Green Gas

An introduction to biomethane

Green Gas Production

Green gases are renewable and low carbon gases that can be used in place of fossil fuels, reducing carbon emissions in the heat, power, and transport sectors. They include biomethane, bio-propane, and hydrogen.

The GGCS defines “green gas” in its scheme rules here.

The main type of green gas produced in the UK is biomethane, with over 80 plants connected to the grid. You can see the green gas producers that participate in the GGCS here.

Biomethane plants start by breaking down organic matter with bacteria in an oxygen-free environment, a process known as Anaerobic Digestion (AD). The resulting biogas contains a mix of carbon dioxide and methane. The carbon dioxide is split off from the methane, other impurities removed, and then the resulting biomethane is injected into the gas grid.

Network operators closely monitor the biomethane being injected ensuring it has the correct composition and can be used in existing pipelines and gas appliances. The Environment Agency and WRAP have also published a Quality Protocol which outlines the status of biomethane as a product and not a waste.

The organic matter that fuels the AD process (the feedstock) can come from different sources, such as arable crops grown close to the plant, food waste collected from homes and restaurants, waste water treatment plants (sewage works or residues from processes such as whisky distilling and cheese making.

The government supports biomethane production via the Non-Domestic Renewable Heat Incentive (RHI) and the Green Gas Support Scheme (GGSS). The government places strict sustainability criteria on the biomethane production process. This ensures that any crops used as feedstock cannot be grown on land that has been converted from valuable natural habits, and that the production process has a carbon footprint at least 60% lower than the European average for emissions from heat generation. Many producers achieve reductions well in excess of 60% and AD plants also provide a valuable method for dealing with organic waste products, while generating a high-quality fertiliser that is used by farmers around the UK.

Alternatively, biomethane supplied to vehicles may be rewarded under the Renewable Transport Fuel Obligation, in which case similar sustainability criteria will also apply.

Renewable Gas Guarantees of Origin (RGGOs) issued by the GGCS always contain information on the type of green gas produced, the feedstocks used, and sustainability criteria that have been met.

For more information about the GGCS’s involvement with bio-propane and green hydrogen please contact the Scheme.

Transporting green gas

Biomethane in the UK is, in almost all cases, injected into the gas grid where it mixes with fossil gas and it is not possible to track the actual methane molecules. Most biomethane in the UK is injected into the lower pressure distribution network, although there are now plants injecting into the higher-pressure transmission system. Physical gas flows are determined by supply and demand in different parts of the grid, including flows through international interconnectors that connect the UK to Ireland, Belgium and the Netherlands.

In some cases, biomethane may be physically supplied to a consumer for example if a vehicle filling station is built at the biomethane production site or if the gas is compressed or liquified and transported to a consumer by road. The GGCS system records which type of delivery method is used.

"Using" green gas

RGGOs do not track actual molecules of biomethane, and consumers who take gas from the grid should not claim to have physically consumed units of green gas. However, RGGOs do allow consumers to match their consumption to green gases produced and claim to have bought that gas and own the associate environmental benefits.

This concept of “Certificate backed” green gas consumption is firmly embedded in government and market-based rules on energy use, such as the first and second European Union Renewable Energy Directive’s, green gas supply to households within the Green Gas Levy and use of biomethane under the Renewable Transport Fuel Obligation.

However, recognition of the consumption of green gases via the use of RGGOs, or equivalent Certificates, varies between different schemes and regulations. Different requirements can apply such as using RGGOs from particular time periods or meeting further requirements such as proving a green gas has been mass balanced.

The GGCS can provide information and signposting to consumers on a variety of schemes and regulations, e.g. CDP, Green Gas Levy, Green House Gas Protocol, but the recognition of RGGOs as evidencing green gas consumption is always determined by the internal and external stakeholders unique to each consumer.

Further information:

Official Information Portal on Anaerobic Digestion

Information on the non-domestic renewable heat incentive

Information on the Green Gas Support Scheme


Founder Partners and Associate Members:
British Gas
Thames Water
Milton Keynes Council
National Grid
CNG Services Ltd