Executive Summary
Pillar 5: Gas Quality Regulations defines clear standards for parametres such as methane content, impurities and moisture, ensuring biogas can safely and efficiently replace natural gas and solid fuels. Quality criteria for biogas will enable its use for cooking, generating heat and electricity, injected into the gas grid, and in vehicles, expanding market opportunities. Governments can play a crucial role in developing a regulatory framework for biogas, biomethane and bio-CO2, implementing technical safety and enabling offtake and smart grid initiatives.
The recommendations exemplified in this pillar serve as a blueprint for governments to ensure the safe and efficient use of biogas.
Conclusion
This pillar spells out the implementation steps needed to be taken by governments to promote a high-performing and viable biogas industry through clear standards for quality, grid connections and offtaking.
PILLAR 5: Gas Quality Regulations
Introduction
Biogas is at the heart of the anaerobic digestion (AD) industry and is often its primary product. Energy security, along with waste management and climate mitigation, is the primary driver for governments to support the industry.
Gas quality regulations for biogas are needed to ensure its safe, efficient and compatible to use with existing energy systems. They establish clear standards for parametres such as methane content, impurities and moisture, ensuring biogas can safely and efficiently replace natural gas and solid fuels. By defining quality criteria, regulations will enable biogas to be used for cooking, generating heat and electricity, injected into the gas grid, and in vehicles, expanding market opportunities.
A robust regulatory framework combined with technological advancements and market integration is needed to drive the sustainable development of the biogas industry.
5.1. Pretreatment of biogas for combustion
Biogas is the raw gas produced by AD or other sources. It is water saturated and contains various contaminants, depending on the feedstock and the quality of the digestion process itself. For this reason, it is best to be at least partially cleaned before combustion and/or transport to an off-site location.
As a minimum, the cleaning must remove water – to avoid complications arising from twin phase flow, to increase the heating value, and mitigate the risk of corrosion in pipework and equipment – and the most important contaminants, such as hydrogen sulphide (H2S), to avoid risks to human health, and volatile organic compounds (VOCs), to reduce risks to appliances at the point of combustion.
Biogas cleaning, or upgrading, is therefore standard practice on almost all biogas production sites, whether small or large-scale.
Depending on the biogas (biomethane) production route, its characteristics might differ and affect the required pretreatment: 1
- biogas from agriculture
- biogas from sewage sludge
- biogas from organic municipal solid waste
- biogas industrial wastewater
- biogas from industrial solid waste
- landfill gas
- gasification (producing gas from solid fuels).
5.1.1. Direct combustion
For small-scale biogas production (less than 100 m3/h), direct combustion can be the best option. This is because small flows may not be economical to process or large enough to be suitable for transportation to another location. It may also be more practical to use biogas at the production location, particularly at microscale, but it must be borne in mind that the contaminants in raw biogas must be known and managed to avoid risks arising, for example by the use of H2S filters and water traps.
At larger production rates (an estimate would be approximately 100 to 150 m3/h), it is common for biogas to be burned at the production site in a combined heat and power (CHP) unit to generate power and thermal heat and support the production process. However, this is only efficient if the heat generated by the CHP engine can be fully used. Therefore, at larger flows, the option of upgrading biogas to biomethane should be considered before direct combustion.
In addition to the gains in efficiency and energy recovery, this enables:
- use as a direct alternative to fossil (or “natural”) gas, including transportation in existing natural gas networks, enabling direct supply to any consumer at any location
- compression to high pressure for trailer transportation directly to a consumer or injected into an existing fossil gas network grid at an off-site location. (Note that pressurising biogas is technically challenging for various reasons.)
Operating rules and possibly subsidies available to the biogas producer may also make direct combustion less economical than upgrading to biomethane. These economics would be linked directly to the scale of flows, the cost of upgrading and the production location.
Therefore, transportation of biogas should only be undertaken after it has been at least partially dried and H2S concentrations have been reduced or removed. Furthermore, the use of biogas for combustion should be carefully evaluated in comparison to its alternative use as biomethane.
The gas quality recommendations for combustion – and therefore for transportation by pipeline or road trailers – are explained in 5.1.2.
EXAMPLE
The UK government issued Combined heat and power – guidance for renewables 2
5.1.2. Upgrading of biogas to biomethane
The degree of biogas upgrading may depend on the conditions within the gas transportation system and the permitted compositional limits applicable to any given network. These limits may concern chemical composition, heat content (the calorific value, or CV) or both. There are wide variations in the range of gas networks globally. After full upgrading, however, biomethane can be made chemically similar to, and therefore fully interchangeable with, fossil gas.
In general, network entry conditions can only be met by biomethane gas that is dry and free of particulates, with very low levels of chemical contaminants. There may also be specific network requirements: for example, an upper limit on the proportion of inert gases, such as nitrogen.
For road-trailer transportation, biomethane must always be completely dry and have very low levels of impurities.
EXAMPLE
Europe has the standard EN 16723-2:2017 that sets specifications for biomethane used as transport fuel. 3 This standard is still being developed to fully assess and limit contaminates such as siloxanes, terpenes and amines. The updated EN 16723-2:2017 is expected to be published in October 2025.
Upgrading removes almost all carbon dioxide (CO2) and other unwanted contaminants. It can be achieved by various, well-proven technologies such as membrane separation, pressure swing adsorption (PSA), amine scrubbing and water wash (or water scrubbing), producing a controlled stream of methane rich biomethane that can be measured and analysed to yield known quality specification, desired flowrate and operating metrics of pressure and temperature.
The contaminants captured in the upgrading process can be valuable. For example, CO2 (typically c.40% volume in many biogases) has established markets, and the CO2 stream can also be processed in a dedicated plant so that its purity can be managed to a desired standard. This presents the opportunity to both displace other CO2 (and work towards making biomethane projects carbon negative) and to be a viable and reliable secondary income stream for the biogas producer. At present, the markets for CO2 are such that many existing biomethane projects are retrofitting CO2 capture plant, and it is becoming standard to include this facility in new projects. Similarly, there can be value in the sulphur captured from removal of sulphurous compounds, most notably H2S .
5.2. Quality regulatory framework for biomethane
All jurisdictions are expected to have their specific arrangements for overseeing industry in general, and energy networks in particular. These may vary in complexion and detailed responsibilities, however there are common characteristics:
- A government-appointed body – a regulator – is established to monitor and develop policies relating to a part of industry. The regulator may have responsibility for commercial matters, safety matters, or a combination of both. These bodies are almost always independent, and (relevant to biomethane) oversee the gas grid networks, which are commercial enterprises that deliver gas from the production source to consumers.
- There is regulatory oversight of safety in operations, cost and resource efficiency, and working practices, against legal obligations, targets and/or comparable organisations.
- There is oversight of regulations and technical standards relating to high-pressure road trailers, the transport of hazardous substances, and road haulage in general.
Globally, there is extensive variation and a wide range of possible characteristics for regulatory bodies and their exact remits of responsibility, whether they are national or local. There is no standard model. They may also vary greatly in their extent of their legal powers and levels of authority. Therefore, it is important to recognise these possible differences, plus any variations in technical standards, when considering biogas and biomethane in any location.
Polices for the biomethane development market can be divided into five groups: 1
- national vision
- direct investment and production support
- indirect production support
- demand-side incentives
- regulations enabling market access.
Policies may be divided further into five areas: 4
- type of policy
- administrative area
- administrative level
- which part of the value chain is addressed
- how policies change over time.
The aim is to aid the policymaking process by helping to understand how the different mix of policies affecting biogas can be developed to improve biogas production and use.
Grid networks or grid operators typically operate under obligations set by their respective regulator(s). Grid operators may be expected to adopt a conservative approach to ensure compliance with regulatory requirements, especially if they are liable under their operating regime for any financial costs or reputational risks. When considering biomethane connections it is, therefore, important that the overarching principles are:
- clear assignment of regulatory powers and their oversight: the starting point should be to do what facilitates biomethane connections while maintaining the required levels of performance, accuracy and compliance with technical standards (and any other rules and limits that may be in place).
- clarity of the associated responsibilities: this attaches to grid operators, biogas producers and transportation operators. This could be complicated, as it may be that different regulators are involved; for example, for energy production and for road transport.
- visibility of regulatory practices: arrangements for audit, inspection and the consequences of non-compliance; for example, the need to report remedial steps taken, or additional demonstration of changes made, etc.
- consistency in application where more than one transporter is operating in any given jurisdiction.
Observance of these principles, regardless of the exact details of the operating regime and existing laws, will provide biogas producers and all transporters, including grid operators, with full understanding of their roles, obligations and liabilities. In turn, this will help reduce any perceived need for excess caution to the benefit of all parties concerned and the biomethane industry in particular.
5.2.1. The preferred regulatory regime for biomethane
Taking the general principles of regulation, the following describes the more detailed aspects, so stakeholders in any jurisdiction can understand how the regulations are applied in practice and what they must do to comply with them.
5.2.1.1. Regulation should be proportionate and specific
Biomethane production is relatively new and generally post-dates regulations applicable to gas grids, both technical and commercial or contractual.
Biomethane grid connections can be considered in two ways:
- the composition of the biomethane compared to fossil gas and/or their grid entry requirements. Commercially available instrumentation can be used to “read” gas composition in real time at any number of sites, simultaneously if required.
- consideration of multiple smaller-volume flows into gas grids, generally at lower pressure tiers, compared to small numbers of bulk supply points feeding the highest pressure tiers. The hydraulic modelling related to capacity planning is more difficult with multiple smaller infeed connections.
Hydraulic modelling is rendered more difficult because the issue is not about peak flow capacity, i.e. making sure the pipes are big enough, but consideration of the local supply/demand balance, i.e. making sure there is enough demand on a network to consume the biomethane at times of low consumer demand.
Taking these points into account, it is much more appropriate to attach specific entry conditions to biomethane connections, and specifically not to treat them the same as larger bulk-supply points. The real effects and operational needs of biomethane production can then be properly considered, and the appropriate operating rules applied. This would yield benefits to both the producers and the grid operator, for example, by enabling simpler requirements for flow notifications, data reporting and information exchange.
Currently in the UK, from a legal and regulatory viewpoint, a biomethane injection site is considered to be the same as a bulk-supply point such as a beach terminal or a liquefied natural gas (LNG) importation terminal. A typical biomethane site may flow around 600 to 800 m3/hr predominantly into the distribution grid, whereas a bulk-supply point will flow several hundred times this amount into the transmission grid. This means that rules written to address the risks of bulk-supply volumes are applied to much smaller flows, where the risks attached are manifestly different.
While this arrangement is simple in that it requires just one set of regulations, it is profoundly undesirable. The biomethane industry is best supported by specific requirements. The areas where clarity and uniformity are needed are discussed in the next sections, with general and more detailed considerations. Thus scale of production should be taken into consideration when designing policies specific to the biomethane industry.
5.2.1.2. Risk-based entry conditions
Biomethane producers should rightly be accountable for all aspects of their production: gas quality, flowrate, delivery pressure, etc. This would address all possible risks the biomethane connection could present to the gas grid operator. These risks comprise only two main areas. The first is the possible flow of biomethane outside the required gas quality limits at grid entry, and the second is the risk of exceeding the pressure limits at the connection point.
It may be that a network has a wide range of allowed gas composition. It is also the case that newer gas grids are made from corrosion-resistant materials. These network-specific characteristics should be identified and taken into account when defining the grid entry requirements and used to reduce the requirement for composition monitoring to the minimum required. This offers significant savings in instrumentation and simplifies data uploading.
Standardised gas pressure control equipment can be readily configured to manage the risk of both under- and over-pressurisation. A pressure regulator arrangement can be easily implemented using widely available equipment; biomethane applications can readily use the devices already available from an existing mature supply chain.
Appropriate levels of obligations are necessary for biomethane producers; there should be no exemption to important gas standards, but focus on only the relevant parametres. For example, for gas quality, after first commissioning, there should be no ongoing requirement to confirm the absence of radioactivity, microorganisms and high methane number constituents, enabling a more cost-effective demonstration of the required gas composition through less sample testing.
5.2.1.3. Harmonisation of connection procedures
There can be wide variations in connection procedures and the associated costs. In the UK example there is a ratio of 10:1 between the cheapest and most expensive network connection cost, and a comparable difference in the time taken from enquiry to completion.
It should be the case that the conditions, approach and costs are standardised; what happens in one location should be the same in another if all other regulations are consistent, and there should be no need for variations in connections to the same pressure tiers arising from different ownerships of the grid in question. Any variation or stated need above the minimum required should be explained and justified by the grid operator so that it is supported by expert opinion, risk assessment and/or actual experience.
Note that this issue has much in common with the injection of hydrogen, where grid operators and regulators are currently active in creating technical standards and regulatory requirements that meet safety, operational and commercial criteria that would apply uniformly everywhere.
In practice, the approach to new connections can vary considerably between grid operators in the same jurisdictions. Also, how regulatory authorities are empowered to enforce compliances also differs widely between jurisdictions. However, experience to date gives overwhelming evidence that biomethane must be able to operate under dedicated regulations that are proportionate to the scale of individual project flowrates and lower levels of complexity.
5.2.1.4. Plant supply responsibilities and ownerships
There is wide variation observed among grid operators in their approach to the supply and operational responsibility for biomethane plant. This is in part due to different regulatory approaches that either inhibit or incentivise different plant ownerships, or offer cost allowances and subsidies to grid operators. Again, there is a huge variation in approach, even among EU member states.
It would be very helpful if the approach to the supply of connection plant and equipment is standardised. This would mean that a biomethane producer would know at the project inception stage what they must provide. Note that this point concerns who provides what; the adoption of technical standards is always required (see sections 5.6 and 5.7).
Experience tells us that biomethane producers can procure the necessary plant more easily and economically than network operators. Further, the producers are better placed to have the expert knowledge and familiarity to specify the plant required and to maintain it when in use. So the most effective model is one in which the grid operator provides the minimum necessary to facilitate the connection (information about the pipe, operating details, locations, etc.) and the producer then assumes responsibility to provide, install and, for the whole project lifetime, maintain all the required plant. This is expected to yield efficiencies in costs, time and reliability.
5.2.2. Allowances for changes and innovations
There should be recognition in grid operator licences and operating code conditions that allow flexibility so existing blockers to biomethane entry to their grids can be avoided by innovation. Naturally, the benefit must be demonstrably linked to the change, and observance of technical standards and good governance must always be maintained, but this can be shown to be achievable.
The outcome would be rewarding grid operators for showing innovative thinking (the reward could be financial, reputational, or other), and the benefit would be a higher probability of new biomethane connections and hence growth in the industry. The most illustrative example of this is reverse compression (see section 5.7.3) in which a simple concept using standard equipment can be easily frustrated by overly complex regulations, grid operator policy decisions, and long periods needed for design procedures.
5.2.3. Active obligation to facilitate biomethane connections
Active obligations should be placed on grid operators who, as natural monopolies, are then encouraged to facilitate and support biomethane connections There should be recognition of successful implementations and corresponding penalties for underperformance.
This would need to be accompanied by corresponding relief for them from actions by the biomethane producer, so the grid operators can be fully objective, and much less conservative, in their perceived and actual obligations.
Taken in conjunction with the point above, this could be a very effective way of encouraging and achieving more, and cheaper, connections.
Furthermore, these regulations must be applied uniformly to deliver the desired outcome; experience in the UK shows how different interpretations and practices can lead to strong variations in practice and resultant degrees of difficulty in achieving a grid connection.
5.2.4. Gas composition tolerances
Where the biomethane input represents a very small flow into a larger volume, it should be desirable and possible to allow some exceptions, or wider compliance limits, that recognise the dilution that will happen, while staying within the aggregate limits required to maintain safety and meet overall grid-delivery gas quality limits.
An example would be oxygen content, where a grid may have a low maximum level (often in the range 0.2–0.5% by volume) to manage historic risks of internal pipework corrosion, whereas dry biomethane would not present any additional risk, allowing a maximum biomethane oxygen level to be increased. This has been achieved in some European cases, where an upper limit of 1.0% oxygen has been implemented by the regulatory bodies. This is highly significant, because most biomethane is made with an oxygen content of around 0.2–0.5%, and removal of oxygen is uneconomic.
EXAMPLE
Variation in the maximum admissible content in European gas networks is shown in Table 1. 5
Table 1. Maximum admissible oxygen content in European gas networks
| Country |
O2 concentration in injected biomethane |
Notes |
| Denmark |
1,000ppm (daily average) at entry points and storage points |
5,000ppm at transition and metreing points for biomethane |
| France |
100ppm mol |
On an hourly basis |
| Spain |
100ppm mol |
For transition grid including UGS (underground gas storage) sites |
| Italy |
6,000ppm |
|
| Netherlands |
5,000ppm (8bar < RTL <40bar) |
5ppm (40bar <HTL <67 or 80 bar) |
| Poland |
Up to 2,000ppm |
|
| Czech Republic and Slovakia |
Up to 200ppm |
|
RTL: regional transmission line – low pressure
HTL: high-pressure transmission line
A similar approach could be taken for other biomethane components, where no risks are presented and a more sensible limit can be adopted, recognising throughout that (a) the risks identified may be historic and not as severe in contemporary conditions, and (b) the same or similar approach could be adopted where small additional amounts are not material to persisting risks.
Therefore, there is a strong case for following a risk-based approach in which the merits and circumstances of a particular site can be considered. A risk-based approach will also meet other criteria.
5.2.5. Metreing tolerances
The adoption of metreing tolerances that are consistent with the scale of flows is recommended. This would mitigate the need for higher-cost equipment, in terms of both capital and operating costs; fewer and simpler metre tests and recalibrations related to simpler metreing would take less time and be less frequent. It would also allow the use of a wider range of commercially available equipment, supporting open choice of instrumentation and opportunity purchasing.
5.2.6. Electronic data exchange
It is recognised that biomethane sites connected to a gas grid must report operational status to the grid operator at some interval. In practice, this can comprise a long list of data about instantaneous and cumulative flows, all control system alarms, outlet pressure, odorant intensity and many other data points.
Instead, this should be proportionate to the impact the flowrate may have on the connected network, rather than an extensive standardised list of data that requires a high degree of electronic complexity and real-time communication. An example would be to allow an end-of-day download of cumulative flows (volume and/or energy), using a simple datalogger instead of the real-time exchange of a high volume of data via expensive telemetry.
5.2.7. Relief from regulatory breaches in exceptional circumstances
There should be consideration given to grid operators and biomethane producers from regulatory breaches that have no practical impact. If a tiny volume (for example < 10m3) of biomethane with a lower CV than normal flows into a network, it has no practical implications and should not trigger the need for immediate action, stopping of grid injection, or lengthy and detailed post-event reports.
This principle should be applied to all aspects of gas composition; only material amounts should be considered to be regulatory breaches. Experience in some jurisdictions demonstrates that there can be much simplification without any impact on overall levels of safety and/or compliances.
The enforcement of regulatory powers should also be appropriate and proportional, so that the many practical differences between low-volume biomethane and higher volume sources are correctly recognised.
5.2.8. Open selection of instrumentation
There should not be any requirement to specify exact instrumentation for biomethane sites or the grid connection. Instead, the emphasis should be on obliging the biomethane producer to install and operate all plant and equipment that meets an established performance standard.
This would allow economic decisions on the selection of plant and instrumentation to be free of prescribed manufacturers, instrument type or accompanying software, so that projects are able to choose from among commercially available plant and equipment, thereby gaining cost efficiencies.
A secondary benefit of this approach would be to expand the supply chain, opening competition among suppliers and expanding the selection available.
5.3. Technical regulations
Many technical regulations in different jurisdictions are very similar. This can be because the standards themselves may be jointly developed in a universal framework, or a country may choose to adopt foreign standards on the basis that they can be readily and easily implemented. An example is the EU, in which all member states apply the same set of technical standards, and those same standards are often applied in other non-member states.
However, it is also not uncommon for a jurisdiction to have its own bespoke set of technical standards. Therefore, it will always be important for any biomethane project to understand and observe the standards relevant to that location.
5.3.1. General and safety-related
Most current regulations are based on a natural gas grid and so predate the biomethane industry. They are aimed, implicitly, at grid companies and place various responsibilities upon them. At risk of over-simplification, the main obligations are:
- to deliver gas within stated compositional limits at a suitable designed pressure to consumers
- to describe and explain how this is to be resourced, arranged and carried out in practice.
Taking the UK as an example, the second point must be summarised in a safety case, which must then be “accepted” by the national safety regulator, the Health and Safety Executive (HSE).
It is to be expected that there will be similar, if different, arrangements under all jurisdictions.
The safety case, or an equivalent, is an important statement of intent and operating arrangements. Given that all networks carry out the same processes, there should be no variations in their approaches to biomethane connections.
All variations will generate costs for the biomethane producer, therefore they are to be minimised or eliminated in order to support biomethane connections, whereas consistency in the application of grid entry requirements will lead to the development of a cost-effective and streamlined step-by-step sequence to the supply chain, project progress and final installation.
5.3.2. Gas quality specification
The basic requirement for biomethane sites is expected to meet the same entry specification as fossil gas at other bulk-supply entry points. As an example, the UK grid entry specification is shown in Table 2. There are many common features, but also some differences, between these and the specifications in Europe, even though the high-pressure networks are inter-connected.
Table 2. UK grid entry specification
| Parametre |
Limit |
Notes |
| Hydrogen sulphide |
<5mg/m3 |
Always required for safety reasons |
| Total sulphur |
<50mg/m3 |
Always required, however demonstration by extended test frequencies would save costs |
| Hydrogen |
<0.1% molar |
Note 1 (notes below) |
| Oxygen |
<1.0% molar |
This is the sole example in the UK of a regulatory limit being adapted for biomethane |
| Impurities
(H₂S, siloxanes, NH₃, etc.) |
Nothing potentially harmful or affecting combustion |
Note 2 |
| Hydrocarbon dew point |
Nothing affecting appliances |
Note 3 |
| Wobbe number |
47.2–51.41 MJ/m3 |
Always required |
| ICF
(Incomplete Combustion Factor) |
|
Discontinued 2022 |
| Sooting index |
|
Discontinued 2022 |
| Odourant |
Required on all UK non-National Transmission System pipelines |
Required, however instrumentation is robust enough to manage risks arising when biomethane is the small flow into a large network |
| Carbon dioxide |
<2.5% molar |
Note 4 |
| Water dew point |
-10 degrees at 10 bar |
Always required |
| Total inerts |
<7% vol |
Note 4 |
Note 1: Hydrogen content is irrelevant and is not a factor in biomethane production, but offline analysis is still required by UK grid companies. The need to measure this can be removed by risk assessment, as there is no hydrogen in biomethane.
Note 2: When applied to biomethane, impurities relate to siloxanes and other VOCs, for which there is no legal limit applied, only the broad requirement stated. As a result, the gas distribution networks have no guidance and are conservative in their approach, leading to varied interpretations and often overdesigned filtration plant at the biomethane producer’s expense. It should be possible to test for impurities at start up and then assume no change unless or until the feedstock is changed.
Note 3: This is also irrelevant as biomethane contains only methane, nevertheless it must be tested for at regular intervals.
Note 4: The proportion of CO2 (and total inerts) is not a regulatory requirement but is set by the operating policy of the grid operator. Other biomethane content is similarly constrained; for example, a maximum 7% volume of propane. (High propane content can be required to meet high CV targets). In either case, the producer should act upon high levels to manage the risk of breaching the allowed limit for the Wobbe number, which is a safety issue. CO2, as an inert gas, does not combust or contribute to enhancing methane’s calorific value and, operationally, it may suit the biomethane producer to flow at around 2.5% CO2 content.
All these limits must be demonstrated. The usual method of doing so is to commit to frequent and expensive sample analyses in addition to the already extensive online analyses required. Some are simply not required in practice.
EXAMPLE
A special dispensation was granted for an increased limit for biomethane with an oxygen content of up to and including 1% (molar) at pressures below 38 bar at grid entry after extensive analysis of old buried pipework demonstrated to the UK HSE that a higher content did not present material risks. 6 Note that low oxygen content is a common requirement in many networks; a risk-based approach can be taken to allow a higher content for biomethane.
There should also be a simple approach taken to the frequency of offline analyses. Every sample test costs money, and there may be few laboratories that offer a field-based sample collection service. Therefore, the approach should be to carry out enough testing without excess repetition or overly cautious frequency. A gas grid operator may insist on excess testing as part of a conservative approach, with no recognition of the costs generated and borne by the biomethane producer.
Other operational regimes may require different entry specifications or different limit values for allowed composition, but Table 2 is an indicative example.
It can be seen that additional costs and operating overheads would be removed or reduced if the applicable regulations were to be made specific to biomethane. This principle would apply in any jurisdiction anywhere in the world.
For biomethane quality specification for transport, some countries, such as the Czech Republic, introduced national standards defining the quality of biogas used primarily for gasoline engines adapted to such fuel, 7 and quality and testing of gaseous fuels with a high methane content standard. 8
5.3.3. Billing and calorific value
It is possible to cash out suppliers, shippers, consumers, etc. based on the volume of gas or the energy it contains in a set period. Most gas metreing is carried out using devices that read volume, and high-flow-consumption sites have added correction for temperature and pressure. This works very well and has the advantage of simplicity. It does not necessarily offer the best accuracy on the part of the consumer, who may pay for energy not received, or underpay when the gas received is above an assumed energy content.
Billing for energy is complex, as it requires the additional conversion from a measured volume using a measured calorific value (CV). There are profound challenges in matching volume flowed and CV in the same period, and in attributing the correct CV to consumers who have only infrequent metre-reading intervals. This attracts huge complexity and requires significant investment in plant, systems and ongoing administration, so billing in energy is also seen to be imperfect.
It is therefore recommended that biomethane billing is carried out in volume only, unless the given jurisdiction already has energy billing.
It is expected, meanwhile, that most jurisdictions will operate under some range of CV control. This may entail either (a) CV enrichment, usually by the addition of propane, or (b) ballasting, in which the CV of biomethane must be reduced by the injection of an inert gas. The difference depends on the particular network and its allowed CV range at entry.
In either case, a producer must comply with the entry specification and arrange plant accordingly. Where enrichment is required, consideration should be given to blending at the entry point as described in section 5.7.5.
5.3.4. Pressure systems safety regulations
Pressure systems safety regulations (PSSR) are specific EU regulations concerning protection against over-pressurising a gas network or pressure vessel. Equivalents are to be expected in all jurisdictions, although they may be quite different in application, and they are an important safety measure. Biomethane grid connections must be able to demonstrate compliances, usually by reporting and confirming the specific devices and settings that control delivery pressure, and updating this information at intervals as required.
These regulations are EU-wide, so compliance is always required by the European Union. To achieve the correct level of safety assurance, quality of installations and management of possible liabilities, it is important that grid operators and biomethane producers are aware of the regulations to ensure biomethane site design, layout, etc. is managed correctly.
5.3.5. Dangerous substances and explosive atmosphere regulations
Similar to PSSR, dangerous substances and explosive atmosphere regulations are EU regulations that require universal compliance. Also like PSSR, there will be equivalents in all jurisdictions. The main requirements are that:
- hazardous zoning (the extent of possible flammable gas in air mixtures) of possible gas releases are correctly predicted
- plant and instrumentation mounted in areas where gaseous atmospheres are likely are correctly rated to avoid generating sources of ignition
- the biomethane production site is subject to overall assessment to confirm that correct measures have been taken to remove or manage risks of fire and explosion.
5.3.6. IGEM and other technical standards
The Institution of Gas Engineers and Managers (IGEM) operates EU-wide and globally. One of its roles is to create and update technical standards and procedures for everything relating to public gas transporter networks, including a standard for biomethane grid entry plants (IGEM/TD/16). 9 Most of these are based on pre-existing technical standards like the ones created by the American Society of Mechanical Engineers (ASME) 10 but are specifically focused on the UK gas industry.
IGEM is recognised worldwide and operates independently of any specific gas company, network operator, gas producer or gas consumer. Their suite of standards available is extensive and open to all registrants in any jurisdiction.
There are also European equivalent standards and procedures, and many are very similar in content. Technical standards such as those produced by IGEM enable and support biomethane plant designs and operations to achieve the required levels of assurance and safety by providing guidance, design principles and required details for conceptual plant arrangements.
It is not mandatory to use IGEM standards for gas installations (including biomethane) outside the UK; however, it is to be expected that equivalents will exist in all jurisdictions and that they will be accompanied by legal obligations to apply suitable standards of one source or another. Therefore, it is incumbent on all biomethane projects to be aware of what is available, and to apply the appropriate standards.
Because almost all plants used in biomethane production are commercially available and not bespoke, all plant and equipment suppliers will provide confirmation of the design standards they have observed. In the EU, for example, this can be summarised as applying CE certification or providing evidence of independent assurance testing, such as that carried out on behalf of the German government by the testing service provider TÜV Rheinland. Therefore, it is easy for any plant and equipment purchaser to be aware of the technical standards required and to verify compliance.
5.3.7. Summary
The regulatory approach should be characterised by dedicated rules that apply sensibly to biomethane (and other small-scale flows), either by developing a rule set for biomethane, or allowing exemptions to existing bulk-flow rule sets.
The regulations relating to biomethane connections should reflect the following:
- a continued approach to safety assurance in all respects
- incentivising grid operators to facilitate biomethane connections and penalising them if they fail to do so, enforced by a dedicated regulatory role
- encouraging a streamlined, efficient and consistent approach by grid operators with penalties for unnecessary deviations and excessive demands for information they do not use or need
- metreing accuracy, by adopting a “low flowrate” standard and the associated simpler requirements for testing and calibrations
- CV control (where needed), recognising the degree to which biomethane may influence overall grid energy measurement, while safeguarding consumer interests
- enabling open choice of instrumentation for flow, CV and gas analysis measurement
- allowing small flow tolerances to rules for grid entry, so that tiny issues do not generate massive costs. This would be the case for both gas quality and volume/energy flow
- simplifying arrangements for gathering and communicating billing and other operational data, for example daily or even weekly accruals, as opposed to real-time
- relief for grid operators against compliance requirements that are only applicable to large-scale flows
- relief for biomethane producers against onerous and expensive plant and instrumentation
- continuing observance of, and compliance with, technical specifications, e.g. materials specifications and working practice regulations
- continuing observance of, and compliance with, EU and other directives, such as PED, ATEX, and their equivalents in the relevant jurisdictions.
5.4. Gas to grid network entry requirements
Getting biomethane into a gas grid requires certain steps and, in particular, the agreement of the relevant grid operators, alongside other considerations attendant to site selection.
5.4.1. Agreement of a biomethane connection in principle
The grid operator should provide all information detailed in 5.4.1 to 5.4.4 as a package to any site developer at the first enquiry stage. This will allow the project developer to compare alternative sites and alternative connection points for the same site (if options exist). This must be accompanied by the following details:
i. The procedural steps by which a connection will be considered, agreed and confirmed. This may be straightforward, especially if the grid operator has connected sites already operating and has carried out the process before. For first enquiry and/or more complex sites, the grid operator should consider any perceived risks and follow a logical sequence of risk assessment to satisfy itself that any commercial, mechanical and regulatory issues are controlled. In either case, the process should be clear and work logically from first enquiry to completed connection, with ongoing liaison during operation after completion.
ii. The preceding point may be influenced by arrangements for third-party contractors to carry out works on connections, and the extent of regulatory guidance that may, for example, require the grid operator to own or specify particular plant. It should be noted, experience shows that connection speed and efficiency, and hence costs, are improved when the project can provide the maximum extent of the works required. In any case, specific requirements and/or limitations should be made clear at the earliest possible stage.
iii. All information required by the grid operator to facilitate the connection and enable biomethane flow must be provided. Grid operators typically face two main risks: the entry of off-specification gas into the network, which can result in non-compliance with safety regulations and/or other legal obligations, and improper control of gas pressure at the entry point, which can lead to exceeding maximum safety limits. Therefore, the information required from the project should not need to go beyond these areas and always be realistic and reasonable. Therefore, the information required by the grid operator should be limited to:
- a) the expected quality and composition of biomethane, given the feedstock and biology proposed
- b) the arrangements for assurance: for example, what instrumentation is provided, how it will be installed, how reliable measurements will be taken, and how often readings will be available (real time, hourly, end of day, etc.)
- c) details of pressure control equipment at the entry point: the systems or devices used to prevent overpressure and protect the grid infrastructure.
- d) an overview of the project operations: how it will be run, general arrangements for maintenance, contact details, and fault and emergency responses.
The detail of the information will vary depending on the extent of the grid operator’s responsibilities and operating licence in any particular jurisdiction. Where there is specific emphasis on, for example, CV (such as in the UK) it is reasonable for the required details to be extensive (in this case, management of CV control within details of gas composition), whereas the risks of general gas quality, for example, should be addressed simply by details of the measurement equipment applied. Where the grid operator’s obligations are less demanding, the information from the site should be proportionate.
iv. To ensure clarity, the grid operator must indicate all challenges that may arise, including those related to the injection point, flows, capacity restrictions, requirements, testing, blending, and other factors. It should also clearly explain the justification and risk area being addressed for each requirement. This allows the project proposer to understand the context and the level of effort needed to deliver the operation. It is common for key suppliers to only provide details of their plant after receipt of a purchase order, in which case some information will not be available at the start of the project.
v. The timeline required by the grid operator, considering the resources available and extent of direct involvement; for example, if the grid operator is providing any plant and/or connection services.
vi. The key stages needed to meet any regulatory requirements and grid operator policies, and what may need to be demonstrated. There should be a clear distinction between a legal obligation that a grid operator must meet and a matter of policy that it has developed; the first is non-negotiable, the latter may be open to debate and may not even be applicable. In the UK for example, the information needed by the grid operator can vary from a simple explanation of the plant to be built, to a fully detailed information package covering all the site plant, from digester to grid connection. This should, and easily could, be made more consistent.
vii. The details and breakdown of all charges and staged payments that the grid operator expects to receive, and at what milestones, to achieve the full connection.
5.4.2. Biogas site location: export connection considerations
Biogas may be made at almost any suitable location where there is sufficient space for the plant, the necessary utilities are available (electricity, water, etc.), and feedstock delivery is available. However, the site location decision process must be supported with confirmation that a successful and economical export connection can be made, and the details provided as required.
The two main alternatives are:
- direct connection to an existing local gas grid
- export by dedicated high-pressure road trailers.
There are clear advantages in export by pipeline, providing the connection is technically feasible, and using an existing transportation system makes sense. Even if road trailers are required (i.e. the “virtual pipeline”), the objective is to achieve a grid connection at a more remote location. For this reason, the requirements for grid entry tend to be the same for either export connection method.
Grid operators can be reasonably expected to have detailed knowledge of all plant across whole networks and the specific area of any proposed connection point. This is critical information and allows consideration of:
- the distance for any required off-site pipeline
- physical ground conditions
- obstructions, e.g. geographical features such as railways, motorways, rivers, etc.
- any export compression plant that may be needed, depending on the pressure of the destination gas network.
In light of the above, the grid operator must provide core information relevant to a proposed connection:
- pipeline material, as this dictates the type, and therefore costs, of the connection. This will often be related to the operating pressure.
- operating pressure and, if applicable, the range this may have, as alternatives may be available and the choice will be influenced by long-term economics (e.g. the operating costs of the compression plant), and the upfront costs associated with longer pipelines
- whether there are any rules that compel the supply and build of any associated plant to be its responsibility
- gas composition range(s) that may apply, the relevant regulations that enforce them, and the implications for the extent and sophistication of measurement equipment needed
- compositional measurements required, and whether they must be online (i.e. in real time) or offline (at predetermined intervals)
- details of any prescribed instruments that must be used. This should allow the maximum possible range of commercially available devices, materials, instruments, etc. that meet performance accuracies and specifications.
Note that this may depend on the grid operator’s obligations, the outcome of any operational licence obligations, safety considerations, and any limits imposed by legislation.
- confirmed third-party contractors that can be engaged to carry out physical works to (a) build the connecting pipeline, and (b) carry out the actual mechanical connection. It is expected that grid operators will have lists of pre-approved contractors and procedures in place to support this. In other cases, all pipework and connections may only be carried out directly by the grid operator.
- relevant quality assurance/supervision technical specifications, including any specific requirements for material sourcing, construction standards, technical standards and working procedures
- confirmed ownership of the connecting pipeline after commissioning, the associated maintenance obligations, and the relevant boundaries and handover points
- details of any costs to be charged up front, and any ongoing costs for project lifetime.
- detail and format of any connection contracts the grid operator will need, given their own internal operating procedures.
These details would apply to both direct and remote (virtual pipeline) grid connection points and should be the same in either case. The outcome is that the project can make a sensible assessment of the export connection and the costs, issues and timeframe involved.
5.4.3. Biomethane export alternatives
Off-site transport of biomethane can be arranged by:
- direct connection to an existing gas grid
- road transport in a high-pressure virtual pipeline to a remote location, to be injected into an existing grid
- road transport for direct use by a consumer.
It is worth bearing in mind that there are sites where these methods operate in parallel; the exact circumstances of local export capacity and other considerations can make this an entirely sensible approach.
5.4.3.1. Direct connection
Direct connection is generally simpler and less expensive. It may need compression plant if the destination pipeline system operates at a higher pressure, and it may also need a long export connection pipeline, the economics of which are dominated by the length, the presence of open ground for excavations, and the pipeline operating pressure.
5.4.3.2. Virtual pipeline to injection site
A virtual pipeline may be preferable given the specific circumstances of the production site. It is possible, for example, that all other site-selection criteria are fully satisfied, and the relative inconvenience of a more complex export connection is still worthwhile when all other factors are taken into account. It may be the only alternative available if there are physical barriers such as motorways. There are sites where a virtual pipeline has been chosen, even though the transport distance is only a few kilometres, because of a rail line.
Both export connection types can be economically viable and can be accurately costed as part of the business case for a biogas production site. Both use existing and readily available technology and plant.
5.4.3.3. Virtual pipeline to consumer
Direct supply by virtual pipeline to a consumer is also feasible but is likely to depend on more complex considerations. There are clear contractual aspects and there must be mutual benefits for such an arrangement to be viable. However, in the increasing usage of renewable gases, new opportunities may arise; many industrial operators need, or want, to discontinue the use of fossil fuels, and there are already several sites where reception and storage facilities have been operating successfully for long periods.
5.4.4. Detailed assessment
The following are key considerations that must be fully appraised and understood. Each relies on close liaison, or clear information from the grid operator.
5.4.4.1. Capacity assessment
Consumption by consumers (particularly domestic) on most lower pressure networks is both seasonal (depending on the extent of heating load) and diurnal (related to living patterns where most consumption is during daylight hours). The combined effect is that night-time consumption can be as little as 1–2% of the maximum daily consumption rate. In turn, this can mean that the rate of biomethane export flow can exceed the rate of consumption in the same period.
This is referred to as a capacity constraint and it can have profound effects. The biomethane flow causes the grid to “fill up”, and the rising pressure at the connection point reaches and exceeds the allowed maximum. Biogas production is usually at steady rate and in practical terms it cannot be turned off. It may be possible to reduce the rate of biomethane production by turning down the upgrading plant, however this is only possible to (usually) about 50% of the design maximum and, more importantly, can easily lead to flaring of biogas. There are also the obvious economic costs from lost production and the loss of environmental benefit.
Therefore, the ability to inform maximum available flowrate at the grid connection with the corresponding awareness of the credible minimum flowrate is essential for plant design and assessment of the project’s economic viability.
It is a key requirement that the grid operator can be reasonably expected to have modelling tools and simulation expertise to calculate grid capacities. It is worth noting that this capacity constraint reality is generally most prevalent in lower pressure network tiers, where seasonal and diurnal effects are more pronounced. Connections to higher-pressure tiers (e.g. 15 bar and above) may be preferable for this reason, even at the added expense of compression plant, and in many networks the operating pressures are directly managed by the grid operator, which can remove the issue completely.
Consideration of grid capacity should, therefore, be feasible and the outcome may well have bearing on site selection. It is known that many sites that are otherwise well suited to biomethane production cannot proceed due to issues relating to export capacity. In all cases where capacity is viable, the outcome is confirmation by the grid operator of a contractual agreement of the maximum grid connection flow for a site, referred to as the Qmax. It is also feasible that this value may be variable during the year, which will complicate economic assessment but still provide known data for assessment.
5.5. Proposed biomethane quality
The quality of biomethane is a function of the planned feedstock. Some materials are more or less reactive, giving a different biogas yield and variation in chemical composition. There are also changes in biogas quality due to variances in digestion biology. This may mean additional plant is required to completely remove all the unwanted contaminants to meet the limits set out for grid entry. For example, to remove siloxanes (often associated with sewage and food waste feedstock), additional interception plant (usually activated carbon vessels, or other means) can be installed.
In almost all jurisdictions, grid operators are responsible for delivering gas that meets the relevant quality rules to consumers. This is to protect the safety and integrity of the networks themselves, but it is primarily to safeguard the connected consumers, by ensuring the gas they receive is within the ranges of composition compatible with the design of their appliances.
Such obligations are important, and deviations must be both actively prevented and robustly managed out. Grid operators, therefore, can be required to pass on these obligations, and they will do this by setting biomethane composition limits and then stipulating the associated instrumentation accuracy and maintenance.This is, therefore, one of the key pieces of information listed in section 5.3 above. It is likely that a grid operator will operate to the same limits on all pressure tiers, which provides consistency and continuity. However, taking the UK as an example, the bulk transmission system has a wider range of allowed CV compared to the distribution networks, and there are marked variations in the detail of gas composition entry specification and its measurement across the four distribution networks.
The case exists for full standardisation of entry specifications, however the main barrier is that each network can apply its own interpretation of the legal and regulatory obligations.
EXAMPLE
The European Network of Transmission System Operators for Gas’ objectives include; 11
work with the European Committee for Standardisation on revision of the standard EN16726, relating to gas quality parametres: hydrogen and relative density; Wobbe Index (WI); sulphur; methane number and oxygen,
work with the European Committee for Standardisation on revision of the standard EN16726 (CEN TC 408), relating to natural gas and biomethane for use in transport, and biomethane for injection in the natural gas grid, 12 13
work on deploying a “smart gas grid” to improve the interoperability of systems and technologies.
Biomethane quality may also influence the selection of biogas upgrading technology. The grid operator may carry out a risk assessment to give quantified understanding of the potential effects and inform decisions on both plant design and the related measurement instrumentation. Such risk assessment is established practice among European grid operators.
The outcome of any risk assessment would be clarity of the plant specification to support mitigating risks, and the associated frequency and extent of gas sampling needed for additional assurance of compliance with grid entry specification.
In practice, therefore, the project makes a proposal for plant design relating to biomethane quality, and the grid operator then accepts or defines modifications required before the project can proceed. There is a risk of inefficiency in this approach; it may prefer a conservative approach and over-specify its requirements, leading to (a) higher costs for what may be unnecessary plant, and (b) a strong tendency for the requirements to escalate as increasingly risk-averse policies arise.
The quality requirements for the use of biomethane as a fuel for transport will be set by the standards adopted in the national regulations.
EXAMPLE
in the EU, CSN EN 16723-part 2 sets the quality requirements for the use of biomethane as transport fuel. This is due for an update in October 2025. 14
5.5.1.1. Confirmed grid connection point
The confirmed grid connection point comprises:
- the specified point where a biomethane connection (direct or virtual pipeline) is planned, including details of the physical location, pressure tier and who has responsibility for building the pipeline and making the connection
- other details, including confirmation of grid capacity and how long this will be assigned or reserved for the specific site. This is important if there are multiple projects proposed, but in all cases the known capacity must be time-limited to avoid any one project being undermined or disadvantaged by another.
Confirmation of the connection point also allows detailed planning and costing of the pipelaying and/or other plant needed, and the preparation of tenders for the works needed.
5.5.2.Required plant functionality at the entry point
Plant associated with biogas and biomethane production must be correctly selected and operated to achieve the intended outputs in terms of volume flow, compositional quality, energy content (CV), pressure and temperature. The key plant functions are detailed in the next sections.
5.5.2.1. Flow metreing
Flow metreing is essential for billing procedures and quantifying revenues. It is usually volumetric, and there are various commercially available metres that are suitable. There should be no need to stipulate a specific type of metre, providing the associated rules for accuracy are being met.
The metre specification should reflect the expected flowrate to the grid or export connection at all times, for the accuracy of both the anticipated highest and lowest flow rate in a variable range.
The metreing technology used (ultrasonic, rotary, coriolis, etc.) can be open to preference. However, it is wise to recognise the associated maintenance requirements, spare parts and servicing required, and the frequency of accuracy validation testing.
It is worth noting that if billing is to be done in energy units, the volume flow metreing must always be attended by an accurate CV measurement, which would be combined from a separate instrument by a flow computer.
5.5.2.2. Gas quality analysis
Gas quality analysis is necessary to demonstrate that the entry specification is being met, and so confirm compliance with the prevailing safety and regulatory limits of the connected grid. The extent and accuracy of analysis may vary between network jurisdictions, depending on historic sources of fossil gas and the design factors for connected appliances.
Analysis can be online with real-time data gathering, or offline at agreed intervals, or a combination of both. In all cases this should reflect the minimum needed to meet regulatory requirements and any site-specific needs.
It is appropriate to provide assurance by carrying out biomethane analysis at first production and, arguably, again at first flow to grid. Some jurisdictions require the biomethane producer to provide several further analyses at first flow to grid, straight afterwards, and following at very frequent intervals. It is questionable whether these additional measurements are needed, especially if there is also online instrumentation that reports every few minutes. Instead, further analysis could be carried out by lower-cost real-time measurement or by periodic offline analyses.
An idealised offline sampling regime should include consideration of the online measurements already in place, the probability of specific contaminants being present, and the biogas feedstock. Sampling should then be scheduled based on the risks arising and reflect the genuine need to demonstrate that any risks are being managed in practice.
5.5.2.3. Biomethane calorific value measurement
Biomethane calorific value measurement is not usually done by calorimetry (i.e. combustion with measured heat output) but by calculating the exact gas composition. This highlights the rationale of frequent high-accuracy analyses, but only for networks in which highly accurate CVs are important. Elsewhere, the calculation of CV can be proportional to its importance to the given network.
The purpose of biomethane CV measurement is to confirm compliance with the range agreed for grid entry and, in networks where billing is carried out in energy used, to enable calculation of the total energy supplied (volumetric flow × CV per unit).
5.5.2.4. Calorific value control
If the biomethane CV is too low to meet grid entry specifications, it may need to be increased. The established method is by injection of propane, in which the richer propane is used to top up the CV of the combined biomethane/propane flow to the required value. This requires on-site propane storage (typically c.12 tonnes) and sophisticated flow controls to manage the rate of propane injection to meet the target range. Not all networks need this.
A typical CV range is 38–41 MJ/Sm3, but this can vary significantly. In some jurisdictions, some grids operate at much lower CVs, in the region of 30–35 MJ/Sm3. In low-CV grids, it may be necessary to ballast the biomethane, as most of the existing upgrading technologies produce biomethane with a high CV, around 37.0 MJ/Sm3.
EXAMPLE
Gas grids in the Netherlands operate at a low CV (<36 MJ/Sm3), which is already compatible with unenriched biomethane CV. 15
The Republic of Ireland operates with a wider CV range that biomethane can achieve without enrichment. 16
However, upgrading plant suppliers can adapt their standard designs to suit a low CV requirement, within the limits of the technology in question; for example, a membrane unit may operate in the desired range by passing the raw biogas through fewer membranes. Care must be taken to ensure that the resultant overall biomethane composition is still compliant with the grid entry specification; for example, there may be an upper limit on CO2, in which case ballasting with nitrogen or another widely available inert gas is needed.
The use of propane has obvious environmental disadvantages. For this reason and because of the inherent complication it creates, it is undesirable. In all cases, it should also be borne in mind that wherever possible, the need for CV enhancement should be avoided. This can be done by:
- allowing the biomethane to deviate from the grid CV. This may be unlikely, but it could be possible where very high rates of dilution are available so that the smaller biomethane flow has no material impact on the overall grid CV. This might be the case, for example, with a connection to a high-pressure, bulk supply grid.
- actively blending the biomethane with the grid gas using a pipework configuration, or a dedicated mixing device installed for this purpose. Installing monitoring equipment that can confirm the blended CV and its compliance is readily possible. It is also possible to have propane injection as a backup if the mixing gas has an inconsistent flow rate.
- localised billing systems, in which consumers directly supplied with biomethane could pay a lower tariff that reflects the energy content they are getting compared to the same volume of natural gas.
5.5.2.5. Pressure control
It is always necessary to control outlet pressure at the appropriate value for the connected grid at the connection point. This usually includes multiple devices to make the control tolerant of possible faults, and to protect against overpressure (a requirement of the Pressure Equipment Directive 17 ). Generally, outlet pressure needs to be set as high as possible (but no higher than the maximum allowed) to make the biomethane feed the primary source into a network so that it is not “pushed back” by other feeds. The grid operator needs to agree to this arrangement, and historically this has been achieved.
Pressure control equipment is standard and in widespread use, applying the same plant as the established fossil gas industry.
5.5.2.6. Telemetry and data gathering
Telemetry and data gathering is required to:
- enable remote operation of plant at the site and grid connection level
- support billing procedures.
It is important that the grid operator has the ability to “see” whether the biomethane plant is operational or not, and the measurement of flowrate into the network. The principle should be that the plant is designed and operated so that a deviation from entry specification automatically stops the export flow. The grid operator therefore has confidence that all regulatory obligations are being met whenever there is a flow.
This principle requires the site plant to be designed and operated to ensure this “flow stop” functionality is reliable, which is technically entirely feasible. The grid operator should be entitled to review the related design specifications to be satisfied of functionality and reliability. In some cases, the grid operator may require additional protection, to be agreed on a site- or network- specific basis.
Flow data should be collected automatically so that the instantaneous flow and cumulative flow are available from electronic memory and uploaded when required. The minimum requirement should be on an end-of-day basis, using established electronic communications such as the mobile phone network.
It is recognised that requirements for operational and billing data provision may vary across jurisdictions, but the principles of simplicity and proportionality should apply.
5.5.2.7. Compression plant
Compression plant is needed when the connected pressure tier exceeds the biomethane production pressure, or to fill trailers used for virtual pipeline export. It is expected to be generally advantageous to build compression plant at the grid connection site, so that the interconnecting pipeline can be operated at a lower pressure and so incur lower build and operating costs. This requires reference to the specific regulatory regime for plant ownership, third-party construction and the project responsibility to procure the necessary land.
The grid operator should not require any role on the specification, procurement or operation of compression plant, other than to confirm the connected pipeline operating pressure limits. However, the biomethane project should confirm and make available all relevant details to demonstrate compliance with applicable standards and regulations.
5.5.2.8. Odorisation
It is a normal requirement to give gas a characteristic smell to support the detection of leaks in site and public environments, and so support overall safety. Biomethane is odourless, so this is an almost universal requirement; however, it might not be necessary for high-pressure export connections. High-pressure pipelines in the UK and Europe are generally not odourised.
When specified, all odorisation plant details should be made available by the biomethane project or the grid operator to support demonstration of compliance with the applicable regulations.
5.5.2.9. Standardisation of designs
Taking account of the above sections and data requirements, it is possible to develop a single, standard design for any given network. In some EU countries, e.g. the Netherlands, the requirement for detailed design appraisals is less demanding, but no less effective in ensuring the efficacy and performance of the plant. Overall, the trend should be that larger numbers of installations should provide additional confidence, rather than escalating demands for information.
Wherever possible the application of bespoke designs should be avoided. This is a general requirement so that:
- there are efficiencies in design and build costs through repeat application of designs, bulk materials ordering, etc.
- review procedures that confirm the design is fit for the intended purpose and ensure these are streamlined, to avoid the need to re-review each build
- the supply chain is simplified and other market participants are encouraged to join the industry.
It is recognised that different jurisdictions may require different designs, and there may also be small variations for different flowrates and operating pressures; however, this should not affect the use of repeat designs wherever possible.
5.5.2.10. Standardisation of approach
Consideration of new biomethane connections is expected to differ between jurisdictions because of historic industry practice, plant and network ownership, and local factors. Ideally, the same procedures should be applied in every case; as a minimum, the practices and procedures of grid operators in the same jurisdiction should be consistent, follow the same steps, cost the same and have the same outcomes. This may take some effort to achieve, but all participants would benefit from this consistency.
This principle is underlined by experience in the UK, where the four grid operators have developed sets of requirements for biomethane connections that vary in key respects.
One gas distribution network (GDN) retains ownership of the odourant plant, the others do not. This is a small issue but demonstrates the different policy decisions being made.
Another GDN requires a time-of-flight delay pipe at grid entry; instrumentation at the pipe entry provides readings at approximately 30 second intervals, and the time-of-flight pipe provides this delay, so when there is a non-compliant reading enough time is allowed to prevent off-specification gas from reaching the defined grid entry point. The other grid operators do not require this. This attracts substantial capital costs for the pipework required, an additional analyser and associated control-system changes.
Another GDN enforces the maximum allowed grid entry flowrate by automatically closing the outlet remote operated valve, the others do not. This is completely unnecessary as there is no detriment to the grid itself.
One GDN enforces alarm values for gas composition that are within the legal limits, so that technically compliant biomethane (measured above alarm level but still within regulatory level) is prevented from flowing to the grid. This raises massive cost implications and increased gas flaring from lost export flows.
The impact of these variations is that the costs of processing a biomethane connection payable to the relevant grid operator vary between £12,000 and £120,000. This is clearly unsustainable and demands investigation. Similar variances in jurisdictions with a less well-developed biomethane industry must be avoided.
5.5.3. General Principles: Summary
Grid operators must accept this core functionality. Where additional requirements are stipulated, they should be accompanied by a clear demonstration of their justification and benefits.
They must create a standardised, supportive, streamlined connections procedure that actively supports new connections, based on the minimum data requirements, least-cost methods and fastest timelines. They should be satisfied that arrangements are robust and enough to protect their networks without applying increasing layers of protection, based on experience and the excellent record of the biomethane industry.
The biomethane producer should be given maximum scope to procure commercially available plant and equipment, providing they adhere to and demonstrate compliance with applicable regulations, obligations and performances.
The biomethane producer should have maximum freedom to directly procure services for the connection installation, providing the agents meet safety and quality standards.
All plants should be fully functional and meet all performance and technical standards while observing the principles of efficient costs, operating simplicity, factory assembly, and standardised design.
The grid operator must provide all information necessary to support site selection and efficiency in achieving the connection. The operator should specifically avoid being involved in plant design unless it is directly relevant to the safe and secure operation of the grid.
Table 3. Grid entry practical requirements
| Core requirement at grid entry |
Description |
Notes |
| Flow metreing |
Single stream, low flow accuracy standard for low flow volumes |
Volumetric only, later adjustment for CV if required |
| Compositional analysis |
Infrared devices only, annual calibrations, open choice from commercially available |
No specified devices or software |
| CV control |
In order; avoid/render unnecessary, blending at the entry point, smart grid solution, e.g. local CV charging |
Many site-specific considerations but often feasible |
| Pressure control (active/monitor/slam shut) |
Single stream only |
This is a general standard requirement |
| Telemetry |
Data logger only, hourly or end-of-day upload |
Avoids data intensive network traffic, allows lower-cost computing, removes risk of production being stopped if communications are lost |
| Compression |
As required |
Site producer owned |
| Odorisation |
As required |
Network dependent but probably a standard requirement |
| Design assurance |
Standardised designs to be the norm, single review only to apply to multiple sites |
Removes costs and delays incurred by repeated third-party reviews |
| Plant ownership |
Maximise procurement, delivery and ownership by the biomethane producer |
Procurement and installation by the project reduce costs and time needed |
| Connection delivery |
Allowed by authorised third party |
Avoids delays and reduces costs compared to grid operator, secures the same quality and assurances |
| Costs |
Standardised, following the same procedural steps |
|
5.6. Quality standards for bio-CO2 and possible uses
The upgrading of biogas to make biomethane yields an off-gas stream that has very high CO2 content but includes other gases: chiefly a small quantity of methane, and some nitrogen, oxygen and others.
CO2 is in demand for many and varied uses. It is commercially available as a by-product of other industrial processes; however, this incurs costs of purchase (a function of the production cost) and delivery, plus exposure to variable demand-related prices on the part of the buyer. In comparison, CO2 as an unwanted by-product of biogas upgrading can easily be made available at a relatively low cost, it can be captured and stored easily, and so made available for export or “own use” at a biomethane site.
This can also actively contribute to carbon reduction strategies by offsetting the need for specific manufacture, and if the CO2 made is used local to the production site there are further benefits in reducing the required transportation. It may even make CO2 available to new markets where access and carriage are difficult.
It is incumbent on all manufacturers of biomethane that they achieve the best possible environmental performances – no methane at all should be vented to air. This may well happen, albeit in very small quantities, as no upgrading technology achieves 100% methane capture; nonetheless, it is important to make sure this is minimised.
Because there is a market for it, the CO2 stream has commercial value and, subject to the correct level of purity, is readily sellable. This presents the opportunity for a separate income stream for a biomethane project, or the possibility of own use of the CO2 on-site; for example, in commercial glasshouses.
Various suppliers now make plant available that can intercept and treat the CO2 stream to provide a very high purity product. This is usually in liquid form at a temperature of about -60°C. Liquid-phase CO2 provides the secondary benefit of reducing its volume, so smaller storage vessels are needed, making export by road tanker straightforward. It is well within the ability of standard plant to transfer from fixed-site storage to road trailers.
For new projects, there is a clear business case for CO2 capture, either by selection of upgrading technology that includes liquefied CO2 as a product, or by adding CO2 capture plant to the biomethane production stream.
For existing projects, it is often possible to retrofit CO2 liquefaction plant to achieve the same outcome, depending in part on the existing upgrading technology installed.
In either case, CO2 capture should be the norm for biomethane projects, whether the export is by direct grid connection or by virtual pipeline. Measurement instrumentation is also widely and commercially available.
A median-sized biomethane production plant (approximately 600–800 m3/hr biomethane production rate) may be able to produce around 25–30 tonnes of high purity CO2 per day. This will, of course, depend on upgrading technology, the feedstock in use, and plant uptime.
There are existing biomethane sites that directly market CO2 to potential buyers, and some that operate CO2 trailers and so can provide a delivery service to end users.
5.6.1. CO2 purity requirements and specifications
In practice, high purity CO2 is of critical importance to its proposed use. It is, therefore, essential to be able to measure and confirm the desired purity.
Additionally, there may be local uses of CO2 that do not require high purity. An example is large-scale greenhouses, in which it is common to use CO2 to stimulate growth of the vegetable product. In such cases the specification can be relaxed, and only specific local use requirements are met. Local CO2 can, however, provide a significant cost saving against imported CO2; there are examples of growers developing a biomethane project in which they use the vegetable waste to contribute to the feedstock used, export the biomethane as in other sites, and then directly use the CO2. Other sites have developed commercial scale greenhouses to use the CO2, opening up a separate new income stream.
Applications of CO2 can be briefly summarised as:
1. Direct use:
- scientific research: the highest purity is needed to support accuracy of associated tests and investigations
- industrial uses in the chemical industry: as an inert gas for welding procedures, refrigeration, etc.
- food and beverage industries: for carbonising drinks, refrigeration processes, etc.
- medical uses: including wide-ranging routine procedures and research
- farm-based applications: in greenhouses, slaughterhouses, etc.
2. Conversion:
- fuels: synthetic methane, methanol
- chemicals: polymers (plastic), etc.
- building materials: cement, concrete, etc.
The purity required for different uses is matched to how critical purity is to the process. For example, for food and beverage applications the CO2 must be free of anything potentially harmful in consumption and must also be free of any contaminants that might affect the flavour or smell of the main product. Even trace levels of some contaminants can be important. Therefore, a potential buyer can be expected to stipulate a total specification for the CO2 dependent upon the specific end use.
Table 4 identifies the potential uses of CO2 (and therefore customers) and the associated levels of purity required.
Table 4. CO2 purity associated with different end uses
| Use |
Required purity % |
| Technical research |
99.999 |
| Lasers |
99.95 |
| Beverage carbonisation |
99.9 |
| Food |
99.9 |
| Dry ice |
99.8 |
| Medical and industrial, including agricultural |
99.5 |
CO2 is a strategically important gas in the manufacturing industry, especially in the food and drink production sector. Traditionally, the majority of CO2 has been sourced from the production of ammonia for mineral fertilisers, which heavily rely on fossil fuels. To assist in mitigating the emissions associated with fertiliser production, biogenic CO2 captured through AD can be considered a viable option for market development.
A representative total CO2 specification that meets food and beverage industry standards is shown in Table 5.
Table 5. Example food and beverage industry CO2 specification
| Contaminant |
Specification |
Units |
| Purity of CO2 |
>99.99 |
% |
| Water moisture |
<20 |
ppm (parts per million) |
| Oxygen |
<20 |
ppm |
| Carbon monoxide |
<5.0 |
ppm |
| Total methane hydrocarbons |
<50 |
ppm |
| Total other hydrocarbons |
<20 |
ppm |
| Nitric monoxide |
<2.5 |
ppm |
| Nitric dioxide |
<2.5 |
ppm |
| Ammonia |
<2.5 |
ppm |
| Total sulphur compounds |
<0.1 |
ppm |
| Acetaldehyde |
<200 |
ppb (parts per billion) |
| Methanol |
<10,000 |
ppb |
| Ethanol |
<20,000 |
ppb |
| Benzene |
<20 |
ppb |
| Colour |
Clear in water |
|
| Odour |
None |
|
| Taste |
None |
|
It should be noted that modern plant available to biomethane sites, and can be readily incorporated within them, is able to exceed these stated levels of purity.
It is to be expected that performance parametres would be agreed between the purchaser and the supplier of the plant and equipment to enable CO2 production that complies with the required specification. This would be made to fit “back-to-back” with the expected, or targeted, CO2 sales specification agreed with the CO2 purchasers.
5.6.2. CO2 marketing and sales
In all cases, it is both credible and appropriate to describe the CO2 as originating from renewable and therefore sustainable sources. This is the source of a premium value attached to CO2 sales over and above biomethane sales; many energy users want to publicly highlight their environmental credentials, and being able to make open statements about sourcing from suppliers, managing the cycle of waste to energy, and also using the by-products is highly attractive.
CO2 is always made alongside biomethane, so it can be monetised in direct relation to the production rate under suitable contracts.
As a supplier of CO2, it is necessary to be able to demonstrate the appropriate level of quality assurance, confirming that the plant and product streams are correctly specified and operating to the requisite standards. The recognised way to do this is to gain ISO accreditation under ISO 14001 and 9001 (or equivalent quality control standards). This gives potential buyers confidence in a reliable supply that meets their specific needs.
However, another CO2 specification criteria may arise which is a matter of preference, as opposed to chemistry. Experience shows that some potential purchasers may choose to buy only CO2 from sources that can be defined as of “vegan” origin. In practice this means that no AD feedstocks can have animal (or non-plant) content. This may be an exclusive requirement, or perhaps an additional threshold content issue where feedstock will need to be, for example, 90% vegan, but it is a criterion that must be recognised and reflected in sales markets and contracts.
The value of CO2 is expected to be set by agreement at contract stage. There are no other parametres and the market should be open. It is not expected that there will ever be a fixed price, but it would be normal to expect that competition among suppliers will have some bearing on the general market value, as will the overall balance of supply, demand and location.
Multiple biomethane producers in various jurisdictions are now marketing their CO2 directly to potential customers. This is encouraging to the biomethane industry as a whole and is expected to increase. There are also many sites known to be retrospectively installing CO2 capture plant after several years of operation; this underlines the robustness of the business case.
5.7. Regulatory framework for gas off-takers, gas exchange arrangements
5.7.1. Gas consumer connections
The off-taking of gas by a consumer generally requires only a physical flow connection and a suitably sized and registered metre.
However, the ownership of metreing equipment and the connection pipe, and the procedure by which a connection is installed, maintained and operated can vary substantially between jurisdictions. In many examples:
- The physical connection is, in effect, an extension of the gas network. However, rules vary about the location of the metre position; for example, at the consumer boundary or within consumer premises.
- Ownership of the flow metre is sometimes the responsibility of the gas network operator, in others it is owned by a dedicated metreing agency. This is important because ownership is associated with responsibility for specification, accuracy and ongoing maintenance (including periodic testing and replacement).
- It is to be expected that technical standards relevant to metre housings, access security, pressure/temperature correction and remote reading capability will also be specific to jurisdictions.
Chemically, biomethane and fossil gas are almost completely interchangeable. In addition, biomethane that flows into the network will be blended with the fossil gas already present and transported from the injection site according to the flow pattern created by the consumers. It is the grid operator’s responsibility to ensure that security of consumer supply by the network is maintained, so that there is enough capacity to meet demands (see section 5.7 on “Smart Gas Grids, Methods and Initiatives”).
It should, therefore, be the case that all connections to consumers should always be the same, regardless of whether it is expected to convey fossil gas, biomethane, or a mixture of both. This means that no modifications are required if an end user changes from fossil to biomethane, or operation of the gas grid causes this to happen.
The exception would be the case of a dedicated biomethane pipeline; this would be purpose-built but use exactly the same materials and construction as all other networks.
The rules and regulations for the operation of existing off-take connections (and specifically the process for providing new connections) will be specific to any given jurisdiction. In general, it should be confirmed whether a new connection is inclusive of:
- the metre, and any specific metreing ownership rules
- any required pressure reduction equipment
- any requirement for metreing pressure and temperature correction, and associated datalogging (for large-scale sites)
- where the metre will be located relative to the site
- whether any economic test is applied to the provision of the new connection – for example, in the case of long network extension or capacity reinforcement – and the resultant consideration of costs to be borne by the connecting party.
It should also be a reasonable expectation that any existing grid operator could confirm all the above or make the process for application for a new connection publicly available. This would support the application of any user, including one wishing to use biomethane.
5.7.2. The renewable gas premium
5.7.2.1. Regulations and incentives
Various countries currently have governmental initiatives to target the transition to renewable energy. An example is the Renewable Energy Directive (RED) being implemented in the EU. This gives member states specific targets to be achieved to a specified timeline, providing a binding incentive to achieve staged transition, and all member states are committed to following this.
The RED has progressed from RED II to RED III (the latter to be implemented in 2025) to target the more challenging headline achievement of 42.5% renewable energy use by 2030 (plus several other more specific targets). The EU also applies a Fuel Quality Directive and other measures intended to support progress towards achieving the terms of the Paris Agreement on climate change.
The German organisation NOW GmbH – National Organisation Hydrogen and Fuel Cell Technology, in English – has published a summary of the changes between RED II and RED III that will affect transport (see Table 6). 18
Table 6. Adjustments affecting transport targets between RED II and RED III
| Targets 2030 |
Targets in RED II (2018) |
Targets in RED III (2023) |
| Renewable energy in transport |
At least 14% share of renewable energy in final consumption of road and rail transport |
At least 29% share of renewable energy in final consumption of all energy used in transport
Or a minimum of 14.5% reduction in GHGs compared to emissions that would have been created by fossil fuel use instead |
| Fossil fuel comparator (Reference value to calculate baseline for GHG reduction target) |
94gCO₂eq/MJ for all energy used in transport |
94gCO₂eq/MJ for electricity used in transport
94gCO2eq/MJ for all other energy used in transport |
| Electricity used in transport |
No sub-target
Multiplier of ×4 for renewable electricity used in road vehicles and of ×1.5 for renewable electricity in rail |
No sub-target
Multiplier of ×4 for renewable electricity used in road vehicles and of ×1.5 for renewable electricity in rail |
| Advanced biofuels (feedstocks listed in Annex IX, part A) |
3.5% share of advanced biofuels in final consumption of road and rail transport×2 multiplier |
5.5% share of advanced biofuels and renewable fuels of non-biological origin (RFNBOs), in final consumption of all energy supplied to transport, with a 1% RFNBO minimum share
Indicative goal of at least 1.2 % of energy used in maritime transport to come from RFNBOs in 2030 |
| RFNBOs |
No sub-target
Additional multipliers in aviation and maritime transport: ×1.2 |
×2 multiplier for advanced biofuels and RFNBOs
Additional multipliers in aviation and maritime transport: ×1.2 for advanced biofuels and ×1.5 for RFNBOs |
| Biofuels and biogas from used cooking oil (UCO) or animal fats (feedstocks listed in Annex IX, part B) |
Use of biofuels and biogas from UCO and animal fats is limited to 1.7% in final consumption of energy in road and rail transport×2 multiplier |
Use of biofuels and biogas from UCO and animal fats is limited to 1.7% in final consumption for all energy used in transport×2 multiplier |
| Conventional biofuels (food- and feed-based) |
Share of conventional biofuels consumed in 2020 in road and rail transport in member states +1%, but a maximum of 7% |
Share of conventional biofuels consumed in 2020 in the transport sector in member states +1%, but a maximum of 7% |
Other countries apply specific incentives schemes in the form of cost subsidies, feed-in tariffs, financial investment sharing and other mechanisms to encourage production of renewable energy.
There are also many other national and international schemes for allowing subsidies and certifications related to environmental performances. The International Sustainability and Carbon Certification scheme (ISCC) applies to agricultural products (including forestry) used as actual or potential AD feedstocks to verify that sustainability criteria are being fulfilled.
There is, therefore, significant incentive for proliferation of biomethane use as part of the suite of renewable energies, and production of renewable biomethane at every opportunity. There is also an active set of agencies and industry bodies operating at national and international levels to monitor, manage and report on performances being achieved in terms of sustainability.
The importance of achieving compliance with schemes applicable to the relevant jurisdiction and/or international agreement is immediately relevant to biomethane producers and, as is observing the detailed rules and criteria that apply. Gaining the right certifications and demonstrating the relevant compliances is critical, and clearly there are also economic gains for both producers and consumers if they can qualify for incentive schemes.
5.7.2.2. Premium values and certifications
In light of the above, renewable biomethane generally attracts a premium value; it can be very attractive to consumers who are targeting a reduced or negative carbon footprint, with the associated reputational gains, and are, therefore, interested in acquiring renewable energy, even at a higher cost.
Additionally, other consumers may want to change their energy source from higher-cost or more polluting fuels, and in doing so want to make the most environmentally attractive change possible, which can also be expected to increase demand for renewable energy. An example would be the replacement of transport fossil fuels with biomethane. The scope for this is enhanced by the possibility of virtual pipelines, but it can also be achieved using new grid connections.
It can be seen that there is scope to monetise the renewable characteristic of biomethane by accounting for the volume and/or energy involved, and then using the principle that flowing a given volume into the gas grid can be considered to be an equivalent volume off-taken at any other place on the network.
An accounting and certification system can therefore be envisaged that can register, or “certify”, a volume or total energy at a given system entry point and match that to one (or more) points of consumption. The gas molecules are not the same, but the volume they represent always balances out.
The qualifications required for certificated biomethane would be:
- compliance with all rules relating to sustainability of feedstock
- meeting standards of efficiency in production
- traceability of the volume (or energy) involved.
A credible body with recognised permanency, reputation and resources (e.g. ISCC, REDcert, Better Biomass) is required to promote, monitor, audit and manage the financial marketplace, and would be needed to ensure the confidence of users. This body would be accountable to the appropriate regulatory body in any given location and could be licenced itself as a type of market operator.
Any accounting system can be made to operate in either volume or energy; a certificate can attach to a quantity of cubic metres or kilowatts. Volumetric reconciliation is far easier to administrate and operate. The complications of reconciliation in energy should not be underestimated. In jurisdictions where general billing of gas sales is carried out in volume, this would become the default for the certification scheme.
We can see that a premium value can be established in two main ways:
- agreed directly between counter parties under a form of contract, where a producer finds a buyer and they agree a mutually acceptable premium value
- a market for certificated renewable gas can be created in which buyers bid for and pay the premium value of each unit of biomethane.
The producer can then expect a premium cash return per cubic metre (or kilowatt) of biomethane calculated from the price agreed, or as established in an open market.
In its simplest form, the consumer would purchase a volume of gas at price X, and/or a volume of biomethane at price X + the renewable premium, which could be a fixed value or discovered by market activity, usually covered by proof of sustainability (POS) and energy attribute certificates (EAC) value.
A key point is that the market must clear at a set interval so that producers and consumers cash out to a known timetable, and that the value of the “renewable” component is published so that it can support and record all the transactions completed and so enable settlement. Over time it may be expected that market activity will establish the value of the green premium, and that this will vary according to the perceived value to purchasers and the relationship between supply and demand.
In either case, at all times the “market” for renewable certification must exist in parallel to, and independent of, the gas commodity markets in any jurisdiction.
Biomethane producers will, therefore, sell the gas in existing markets under known contractual terms and receive payment in the usual way. They will also receive further income from the buyers of the “renewable” premium value.
5.7.3. Regulatory oversight
How such markets and opportunities are regulated is specific to a jurisdiction, depending on the powers of the regulator and local laws.
It is to be expected that any direct contract between a biomethane producer and seller (the simplest model) would fall within the governance of the contract laws of that jurisdiction, as the basis is a simple buy-and-sell contract agreed by two signatories.
Following this principle, the usual rules of contracts would apply, with given parametres, prices, exclusions, time durations and default clauses, etc., sufficient to enable a buy-and-sell arrangement to operate as intended.
Many countries, however, operate the gas grids under dedicated regulations overseen by an appointed regulator with specific powers. The UK model is designed to ensure that end users receive and pay for the energy received. This is considered to offer better protection of consumer interests. In addition, regulatory oversight considers the “gas chain” as comprising separate functions for production, bulk transportation, shipping, metreing, billing, gas purchasing and sales, and all participants in these separate activities are licence d so that, for example, a gas producer cannot also be a gas shipper. The regulator also oversees the Green Gas Support Scheme, in which biomethane producers receive a cash subsidy, with certain stringent conditions applied, for their produced renewable energy.
This operating regime is set out in the Network Code, which includes all aspects of the obligations and responsibilities of all organisations (except producers) involved in the UK gas industry. This may be described as representing the more (if not most) complex regulatory approach for any gas industry. There are, however, several European and other countries that operate under rules and regulations that are similarly complex, and in which the assignation of roles and responsibilities are quite different.
Continuing the UK example, there are two parallel independent schemes in operation to facilitate the renewable gas premium market. In both cases, the schemes operate a publicly available market under regulatory oversight in which market trades identify the value on a day-to-day basis. Participants are licence d and can trade certificates as they wish. Market bulletins are published to announce prices and volume of trades completed.
Similar arrangements are being developed or already apply in other countries. Clearly it is possible to introduce gas exchange arrangements in any jurisdiction if there is enough volume available to support multiple trades and they can be suitably regulated.
5.8. Smart gas grids, methods and initiatives
Many otherwise viable biomethane to grid projects cannot progress due to export capacity constraints. A constraint is present where:
- There is insufficient flow capacity for the proposed flowrate of biomethane. Typically, this is because the biomethane site is in a rural area close to the extremity of the grid operator’s system where pipes are small diametre.
- The gas demand exerted by consumers is less than the biomethane production rate, at least for some of the time.
This is the most frequently arising scenario affecting export capacity in fixed pipelines, and can be daily, seasonal or both. The possible methods of overcoming capacity issues include:
5.8.1. System reinforcement
It may be possible to alleviate bottlenecks in pipe systems with additional pipework, or the connection of previously separate networks. This is strongly a specific network issue in both cause and resolution. Additional pipework usually attracts high costs, which in most cases the biomethane producer would be expected to cover. There would possibly also be issues relating to the allocation of costs if another project (or consumer), at the same time or later, gained advantage from the system reinforcement. This solution is, therefore, unlikely to be economically feasible unless it is part of a larger scale systemic expansion of the gas grid.
5.8.2. Active network pressure management
At its simplest level, this is the adoption of seasonal network pressure settings made by manual resetting of other local system input feeds. This can help with smaller constraints by reducing pressure, so making headspace in the pipework to absorb more biomethane.
A more sophisticated method is to install remote pressure control capability, in which the network pressures can be adjusted by remote control or automatically to a timed schedule. This is usually done seasonally, but it can also be daily, or even hourly. This technology has been available for many years and is in established use. Costs are less than reinforcement, but the benefit tends to be modest.
Demand-activated regulator systems can also be installed, where the input feeds to a pipework system can be made to decrease operating pressure in response to daily pressure decreasing . This approach can be complicated to install and is not feasible on networks with multiple input sources.
Input feeds and hence pressures in a network can also be automated based on remote measurement of the extremity pressure. In this system the lowest pressure point is identified and an instrument attached, sending a pressure value to instruct an input feed to change so that the low pressure required is maintained but not exceeded.
In all cases the grid operator is required to assess the best solution and the attendant costs, and to implement the required system. It will also need to absorb or recharge the resultant operational costs for the length of the project.
5.8.3. Reverse compression
Gas networks are designed on the principle of decreasing pressure tiers. Larger high-pressure pipelines provide bulk supplies to off-take points where the pressure is decreased in successive stages to lower pressure tiers. High-pressure pipelines are often under remote pressure control; the operating pressure can therefore be actively managed when overall demands are reduced, which is usually summer and/or night-time periods. The lower pressure tiers, which are more likely to be the connection points for biomethane connections, tend to experience pressure variations as a result of fluctuations in daily and seasonal demand.
It is technically feasible to create extra “demand” in the lower pressure tiers by recompressing a volume back into a higher-pressure tier. Biomethane injected into, for example, a small 7-bar system can be partly or fully compressed into a higher-pressure tier operating at 19-bar (or higher).
Studies have demonstrated that the economics and feasibility of this method are sound. Several such installations are operating in Europe, and there are two under construction in the UK.
There are various advantages to this method:
- The compressor only operates when needed, typically during night-time low-demand periods, and then only intermittently. This compares very favourably to a connection to a higher tier that requires constant compression, with attendant operating energy costs and associated savings compared to permanent compression.
- A single compressor can provide additional capacity for more than one biomethane site. This has happened in the UK already, where several producing sites have co-incidentally connected to the same network.
- The location is usually on land already owned by (or at least adjacent to) a grid company site. This is because the most efficient arrangement is where the lower and high-pressure tiers are co-located, and it also allows efficient use of existing telemetry, civil works, access to infrastructure, etc.
- The location does not have to be close to the biomethane site concerned, broadening the possibilities for site selection.
- European experience shows clearly that the approach is successful in alleviating large-scale capacity issues, as well as more locally. In some cases, it is the only solution to enabling a constant rate of biomethane production in a network with varying patterns of consumption.
This is supported by the case study.
CASE STUDY
This is a site where there is an existing single gas supply feed from a high-pressure (c. 70barg) pipeline into a distribution network supplying a medium sized town at c.2barg. The town also has an effective waste collection system and a large-scale AD with biomethane production. The distribution network has a high CV based on the existing fossil gas supply, and allowed deviations from this value are very small.
The overall gas demand in the town varies daily and seasonally; in the summer the rate of biomethane production exceeds the total demand, and in winter demand exceeds biomethane supply. So, in winter consumers need a supply of combined biomethane and pipeline gas at an unchanged CV, and in the summer the surplus biomethane has to be exported.
Propane storage and injection plant is used to enrich the biomethane, so consumers receive an unchanged gas supply of blended biomethane and pipeline gas.
A reverse-flow compressor is used to push surplus biomethane back into the pipeline in the summer. This is entirely automatic, so that any variations in consumer demand, or in biomethane production rate, are readily accommodated. The biomethane does not require CV control as it is sufficiently blended into the pipeline gas.
This arrangement already exists and is operating at several European sites in France and Germany.
To apply this to new locations would require only the agreement of the regulatory authorities and the biomethane producer to correctly specify and install the required plant and controls. It can also be made to work in networks where there is more than one supply from a bulk delivery pipeline.
A secondary benefit is that the waste generated by the town is also sensibly used, the carbon cycle is well established and the CO2 stream is fed directly to local users.
Grid operators and regulators must facilitate these installations to maximise the potential for biomethane production.
- Network code modifications may be required to meet commercial rules. This has been necessary in the UK to cater for the flows and avoid an impact on transportation charges. This may also arise in other jurisdictions, depending on the nature of the operating regime.
- Grid operators should be incentivised to support reverse compression initiatives. This approach will be critical to maximise the range and number of possible biomethane production sites.
- Grid Operators should allow reverse compressors to be owned by third parties; for example, a biomethane producer or another gas transporter. Experience in the UK has shown that a grid company may refuse, or be reluctant to allow, third-party plant to be embedded in their grid. This will lead to:
- increased costs, because the plant required is not familiar to the grid operators and their designs will be bespoke
- longer lead times as grid operators typically have longer approval and procurement procedures
- complications for assigning charges for electrical power and operating expenditure to the sites that receive benefit.
- Grid operators should also be required to facilitate installations within their existing sites. These are the logical locations as the high and lower pressure tiers are already close together so that the required interconnection can be more readily made, and telemetry and communications links are also present on the existing site.
5.8.4. Smart CV grid solution
Some networks operate under regulations that require very accurate CV measurement; generally this is because consumers are billed in energy, as opposed to the simpler alternative of volume. Such regulations therefore require propane enrichment to increase the biomethane CV, or for the CV to be measured accurately in the network to track the energy content actually delivered to consumers.
Changes to pre-existing regulations to better accommodate biomethane flows are usually very difficult and take a lot of time. However, it may be possible to adapt or redefine billing zones to maintain the accuracy of billing in energy. This will present various technical and regulatory challenges, chiefly arising from the variation in the proportion of biomethane at any given time. However, reducing the size of billing zones, and/or increasing the number of CV measurement points (using a standardised device approved by the regulatory authorities) would be a credible and reasonable method of achieving accuracy in billing while avoiding complex rules changes.
Regulators and grid operators are, therefore, to be encouraged to consider introducing innovative approaches wherever there would be benefits. Note that this is not an issue where gas grids operate without the need for accurate CV control.
5.8.5. Blending at the grid entry point
Biomethane has a CV of approximately 37MJ/m3 (assuming 98% methane content). Where the grid is operating at a higher value then the CV must be increased to match it, and the established way of doing this is by adding propane. This has obvious disadvantages and considerable costs for the biomethane producer.
An alternative is possible. Comingling in a ratio sufficient to bring the biomethane CV very close to the existing grid CV can achieve the target value and remove the need for propane. The ratio needed to have the required effect depends on the relevant CVs of biomethane and grid gas.
Currently in the UK, the regulations allow a maximum variation of only 1MJ/m3 for all flows into the local distribution zones. A biomethane input flow is considered to be one of these input flows, regardless of scale, and the same rules apply, so that only 1m3 of biomethane with a CV that varies outside the 1MJ limit would attract substantial cost penalties. This is a product of the existing regulations.
However, a blending ratio of only 3:1 (fossil gas to biomethane) would be needed to meet even this demanding arrangement, and in many cases this is readily achievable. Blending is installed and active at one UK biomethane site and has worked successfully for several years. Efforts to extend this to other sites have, however, proved unsuccessful so far, even though the methodology requires only standard plant and equipment, designs are already available and no additional flow metreing would be required.
Blending at the entry point represents the least cost and most practical solution to support CV enhancement. It requires limited additional plant:
- a CV measurement device at the grid connection. Where the connection is close to the site this may also double as the main CV measurement point.
- computer-based methodology to calculate the required blending volume ratio compared to metreed flows. This is mainly for assurance that the target CV is being met.
- where necessary, standby propane injection plant, to provide a backup for non-planned circumstances and for additional assurance that target CV can be met. It may never be used.
Blending presents an excellent opportunity to facilitate biomethane grid entry, and it must be incumbent on grid operators to support any opportunities for this system where accurate control of the biomethane CV is required.
5.9. Looking ahead
Effective gas quality regulations are crucial for the sustainable growth of the biogas industry. By setting clear standards for key parametres such as methane content and contaminants, they ensure biogas is safe, efficient and compatible with existing infrastructure. This regulatory framework enables biogas to be integrated into the natural gas grid and used in diverse applications, enhancing market access and investor confidence. Combined with supportive policies and incentives, these regulations drive technological advancements, foster industry expansion and promote environmental benefits. A well-regulated biogas sector is essential for transitioning to a cleaner, more sustainable energy future.
Footnotes
- GreenMeUp: Green Biomethane Market Uptake Project. https://www.greenmeup-project.eu/results/
- “Combined heat and power – guidance for renewables” GOV.UK https://assets.publishing.service.gov.uk
- European Standards DIN EN 16723-2. “Natural gas and biomethane for use in transport and biomethane for injection in the natural gas network – Part 2: Automotive fuels specification”. https://www.en-standard.eu/din-en-16723-2-natural-gas-and-biomethane-for-use-in-transport-and-biomethane-for-injection-in-the-natural-gas-network-part-2-automotive-fuels-specification/?srsltid=AfmBOor7zDi3ZS8JzuZBh5BYdZi1CmhuaibDMmIp7REueJo3Uw6QBtrO
- Gustaffson, M., Anderberg, S. “Dimensions and Characteristics of Biogas Policies – Modelling the European Policy Landscape”, Renewable and Sustainable Energy Reviews, 2021, 135, 110200. https://doi.org/10.1016/j.rser.2020.110200.
- “Biomethane Acceptance in Underground Gas Storage Facilities”, Marcogaz. https://www.marcogaz.org/wp-content/uploads/2022/02/20220214-Biomethane-acceptance-in-UGS-facility.pdf
- “1% Oxygen limit for biomethane injection agreed by HSE”, The Green Gas Certification Scheme (GGCS). https://www.greengas.org.uk/news/1-oxygen-limit-for-biomethane-injection-agreed-by-hse?utm_source=chatgpt.com
- ČSN 656514 (656514). https://www.mystandards.biz/standard/csn-656514-1.12.2007.html
- TPG 90202:2005/Z3 (380902). https://www.mystandards.biz/standard/tpg-90202-2005-Z3-29.6.2021.html
- IGEM/TD/16 Edition 2: Biomethane Injection. https://www.igem.org.uk/resource/igem-td-16-edition-2-biomethane-injection.html
- American Society of Mechanical Engineers (ASME).
- European Network of Transmission System Operators for Gas: Annual Work Programme 2024. https://www.entsog.eu/sites/default/files/2023-07/Draft%20ENTSOG%20Annual%20Work%20Programme%20%28AWP%29%202024_0.pdf
- CEN/TC 408 Project Committee: Biomethane for Use in Transport and Injection in Natural Gas Pipelines. https://standards.iteh.ai/catalog/tc/cen/4a70e2ba-a169-4c8a-97b2-dc59bc46aa93/cen-tc-408?srsltid=AfmBOooFBTz_239TV5bwqndSgwAa1EizWCUOUeFuH9C5srANLzEMUuY2
- Standardization of Biomethane: European Gas Research Group. https://www.gerg.eu/wp-content/uploads/2022/02/2_06_Erik_Buthker_CENTC-408_GERG60th.pdf
- European Standards DIN EN 16723-2. “Natural gas and biomethane for use in transport and biomethane for injection in the natural gas network – Part 2: Automotive fuels specification”. https://www.en-standard.eu/din-en-16723-2-natural-gas-and-biomethane-for-use-in-transport-and-biomethane-for-injection-in-the-natural-gas-network-part-2-automotive-fuels-specification/?srsltid=AfmBOor7zDi3ZS8JzuZBh5BYdZi1CmhuaibDMmIp7REueJo3Uw6QBtrO
- “Calorific values”, Gasunie Transport Services. https://www.gasunietransportservices.nl/en/connected-parties/gas-quality-and-metering/calorific-values
- “Current Gas Flow”. Gas Networks Ireland. https://www.gasnetworks.ie/corporate/gas-regulation/transparency-and-publicat/dashboard-reporting/
- “Pressure Equipment Directive”. European Commission.https://single-market-economy.ec.europa.eu/sectors/pressure-equipment-and-gas-appliances/pressure-equipment-sector/pressure-equipment-directive_en
- Renewable Energy Directive III (RED III) Targets for Renewable Fuels in Transport. https://www.now-gmbh.de/wp-content/uploads/2024/01/Factsheet_REDIII.pdf
