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Home & garden.

21 October 2021

What is green gas?

Find out about green gas, or biomethane, where it comes from and which energy companies sell it.
SI
Sarah Ingrams

Several energy companies now sell green gas alongside renewable electricity. 

Green gas is biomethane and accounts for a very small proportion of the gas in our grid. The rest is natural gas. 

The proportion of biomethane is set to increase as the government plans to help fund enough anaerobic digestion to produce gas for 230,000 homes, starting in autumn 2021.

How is green gas made?

Organic materials (such as food waste and farm waste) are broken down by bacteria in huge tanks, or digesters. The breakdown happens without oxygen so it’s called anaerobic digestion. This produces biogas.

Biogas is then purified and the CO2 is removed, turning it into biomethane. Biomethane has similar characteristics to natural gas so it can then be added to the gas grid and used in homes.

Biogas can also be produced from landfill gas and the gasification of biomass. Find out more about landfill gas and biomass.

Like with renewable electricity, green gas is not piped directly to your home. You’ll get the same proportion as everyone else on the gas grid. The difference with a green gas tariff is that you're paying towards green gas in the grid.

Biogas facility producing green gas

Is green gas renewable?

Yes, green gas comes from a renewable source, such as food waste or farm waste. 

In contrast, natural gas is formed when decomposing plant and animal matter are put under heat and pressure under millions of years. So it’s not easily replaceable in our lifetimes and there’s a limited amount of it.

Biomethane is carbon neutral. It releases emissions when we burn it to heat our homes but is made from organic materials that absorbed carbon dioxide when they grew. Burning it releases the same amount of carbon dioxide so, overall, it doesn’t add more CO2 to the atmosphere.

Cooking on a gas hob

Which companies sell green gas?

There’s less choice of companies that sell green gas than green electricity. They include:

Energy companyPercentage of green gas
British Gas0.02% (10% for customers on its Green Futures tariff)
Bulb3%
Ecotricity1%
GEUK100%
Good Energy10%
Ovo1.01% (15% for customers with the Ovo Beyond Plan upgrade)
Based on energy companies' responses to our questions in August 2021.

Some companies make additional claims for their green gas, for example Ecotricity says its green gas is vegan (made from grass cuttings) and GEUK says that biogas for one of its tariffs comes only from waste (rather than from crops grown specifically to produce biogas). 

Field of energy crops grown to produce biogas

What is carbon offset?

Carbon offsetting is reducing carbon dioxide (or other greenhouse gas) emissions to compensate for emissions released elsewhere. Some energy companies offset the carbon emissions of gas customers in order to state that their gas is carbon neutral.

British Gas, Bristol Energy, Co-operative Energy, Eon Next, ESB Energy, Octopus Energy, Pure Planet and Shell Energy are among companies that offset the carbon emissions of some or all of their gas.

Carbon offsetting usually involves supporting projects that reduce emissions and fight climate change. They can be around the world. Examples include:

  • Tree planting
  • Supporting biomass power plants in India and Chile
  • Supporting a hydropower plant in Bhutan
  • Building wind farms in India
  • Reducing deforestation in Brazil

Look for firms which use verified emission reduction schemes.

Young tree plantation

Is green gas expensive?

Green gas is more expensive than renewable electricity and there is less of it around. 

Like renewable electricity, there are also certificates to show where green gas was produced. These are called Renewable Gas Guarantee of Origin (RGGO) and Biomethane certificates.

These are much more expensive than certificates for electricity. RGGOs cost £6-£8 per megawatt hour in 2020, according to energy consultancy Cornwall Insight.

Some suppliers offer green gas as an ‘add-on’ for which you pay extra, rather than including it in their tariffs as standard.

If you’re looking to cut the carbon footprint of your heating, find out more about heat pumps.