What is green gas?

Green gas (or biomethane) is made from biodegradable materials which can then be used in the same way as energy from fossil fuels – to heat your home or cook with.

The biggest difference between green gas and traditional fossil fuel gas, is that biomethane is renewable and virtually carbon neutral, so it doesn’t contribute towards climate change.

How is green gas made?

Green gas is made by turning organic matter (like plants or vegetables) into biomethane, through a process called anaerobic digestion. This is where bacteria breaks down the organic matter in an oxygen-free environment:

  • Harvest the fuel source. Green gas can be made from a number of biodegradable materials – in our case, we will use grass to create green gas.
  • Anaerobic digestion (AD). This creates green gas, along with a natural fertiliser – which can be used to improve soil quality, in place of harmful synthetic fertilisers.
  • CO2 is removed from green gas. The green gas is ‘scrubbed’, which means the CO2 is removed and the biomethane is then pumped directly into the National Gas Grid.
  • Greening up the National Grid. The renewable gas gets mixed with gas from fossil fuels, to reduce the overall carbon impact of the gas in the Grid.

In theory, we could produce 97% of domestic gas demand from grass by 2035. There’s huge potential for green gas to make a big contribution in reducing carbon emissions and building a more energy independent Britain.

Where is green gas made?

Green gas is made using anaerobic digesters or ‘green gasmills’. Anaerobic digestion is commonly used technology throughout the UK, with more than 500 plants already operating around the country.

However, most existing green gas plants currently operating in the UK use non-sustainable biodegradable matter like:

  • Animal manure
  • Food waste
  • Agricultural crops
  • Crops bi-products
  • Human sewage

Ecotricity’s green gasmills will be the first of their kind in the UK, because they’ll use grass to generate green energy.

Advantages of green gas

Renewable energy

The green gas we supply is recognised by The Vegan Society as 100% vegan. Our green gasmills will help us grow our percentage of green gas – we’ll be able to make gas from completely sustainable plant-material, which won’t run out or emit any CO2.

Our green gas is also carbon neutral, which means we invest in carbon reduction schemes to ensure any emissions we generate get offset.

Create and supports wildlife habitats

We source grass for our green gasmills from land previously used for grazing livestock. This allows wildflowers to grow, which attracts pollinators, and protects the habitats and biodiversity of our wildlife.

A co-product of the AD process is a natural organic fertiliser, which can be used to combat the environmental impact of farm chemicals – which contributes 5% of the UK’s total carbon emissions.

So whether the grass comes from a break crop or permanent grassland, that land will be free of chemicals and artificial fertilisers.

Improves soil quality

A UK government report released in 2016 advised that soil degradation could result in some of our most productive agricultural land becoming unprofitable within a generation.

But by using depleted arable soil to grow a variety of grasses, clovers and herbs for our green gasmills, we can:

  • Improve soil structure
  • Draw up nutrients deep beneath the top soil
  • Increase soil organic matter

This not only improves the soil’s health and fertility – it can also help its ability to hold and release nutrients and water.

It also creates a vital opportunity to combat climate change through carbon sequestration. This is where carbon dioxide is removed from the atmosphere and stored in solid or liquid form – in this case, CO2 would be held in the soil itself.

Supports sustainable food production

By growing our grass break crop in rotation, there are more opportunities for farmers to grow a successful food crop due to the improved soil quality.

And the grass break crop also helps rid arable land of black-grass weed – which effects 25% of arable land in the UK and drastically reduces food crop yields.

Income security for farmers

By creating new opportunities to grow and harvest grass, green gas can provide long-term financial security for British farmers. This offers an alternative to meat and dairy production, which accounts for more than 60% of farming’s greenhouse gas emissions.

Growing our grass break crop also reduces the need for farmers to use expensive chemicals and artificial fertilisers for future crops. They can use the natural organic fertiliser that’s created in the AD process instead.


For more information about our green gasmills and our plans to build more throughout the UK, check out our green gasmills progress.

Reasons to switch

Report by National Grid

"...renewable gas could meet up to 50% of UK residential gas demand. Produced mainly via a process of anaerobic digestion (AD) or thermal gasification of the UK’s biodegradeable waste, renewable gas represents a readily implementable solution for delivering renewable heat to homes in the UK."

Report by National Grid, January 2009