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Ecotricity explains: Making gas from grass

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By Olly Rose
20 Oct 2021

At Ecotricity, instead of paying dividends to shareholders, we invest our customers’ bill money into building new sources of green energy.

Right now, we’re working on a really exciting project, the first green gas mill in Britain – turning grass into gas that can be used in standard boilers to heat our homes and fight the climate crisis.

green gas explained

We want the government to wake up and smell the freshly mown grass; the answer to the question – ‘How should we heat our homes?’ - is growing right under our feet.

We’ve had a lot of questions about how it will work since our founder, Dale Vince, announced the Save our Boilers! campaign in the Daily Express – so here’s our complete guide to making green gas from grass.

Why green gas?
Replacing fossil fuels with renewable energy is a key part of building a green economy - and making our own gas will free us from global fossil fuel markets. As well as the green energy benefits of grass-fed gas, it also provides the economic advantages that come with having jobs and industry based here.

Importantly, it means that the existing gas boilers installed in thousands upon thousands of homes all around the country can still be used in a much greener way. No need to change appliances and send yet more kit to landfill, that’s a really big plus.

What is green gas?
Our green gas will be made from grass material using anaerobic digestion. This means our gas mills will work rather like a cow’s stomach; we’ll feed the mill with grass and harness the biomethane gas which is produced to power the country.

It’s proven technology, this isn’t an experiment. The advantage of grass is that it’s a very clean, consistent feedstock and you can use the waste as fertiliser to grow more grass.

How does the process work?
The grass is cut four times a year and put into a silage plant, which is a big chamber where it sits for a couple of months to break down.

We then put it into a digester, where it gives off a methane-rich gas. We clean it up a little bit and then put into the domestic gas network, ready to use.

green gas

Is it really climate neutral?
When grass grows, it absorbs CO2. We make biomethane gas with that grass and when the methane is burned, it releases the CO2 back into the atmosphere. This means that green gas is carbon neutral over a very short timeframe, just six months from absorption to release.

Fossil gas, by comparison, releases CO2 that is not in the atmosphere now and has been locked up for millions of years; so it’s a net addition to atmospheric CO2.

When will Britain’s first green gas mill launch?
The first gas mill will be just south of Reading and the farmer whose land it’s on will also be growing the grass to feed the mill.

It’s going to be a 5-megawatt plant and will supply about 5,000 homes with gas – for that, we’ll need around 30,000 tonnes of grass each year. We’re expecting it to be in use within the next 12 months.


What does the farmer think about it?
The farmer, Russell Butler, grows grass, wheat, barley, whole crop rye, and maize and forage rye on his farm in Berkshire. He’s passionate about playing this pioneering role in building our very first grass-fed mill because he wants to build a greener Britain.

He also wants to secure a future for his family and thinks that we should be finding ways to create all the energy we need right here rather than importing it from all over the world and having it transported here.

Russell is confident there’s enough land in the UK to produce enough food to feed us as a nation and produce green gas.

How much does the gas from grass cost?
The price of gas fluctuates considerably. Right now, Britain is gripped by very high gas prices and we’re dependent on other countries for 50% of the gas we use. This means we’re really vulnerable to supply chain shocks and price manipulation.

At today’s gas price, green gas is cheaper to make and it has the extra benefits of creating jobs and keeping money in our economy.

How much do the farmers get paid for their grass?
Grass prices on the open market are volatile because of climate change. Crops suffer in poor weather and, as the effects of climate change accelerate in Britain, we’re likely to see more and more damaged crops.

Our commercial relationship with our green gas mill farmer gives him financial security for many years at an agreed price.

What would it cost to deliver green gas to the whole country?
There are 22 million homes on the gas grid in Britain. The current thinking is that hydrogen will take 20% of this load, leaving around 18m homes left to heat.

Our calculations show that 3,000 gas mills will provide the gas needed for all these homes at a cost of just £30 billion.

That might sound a lot but, for comparison, the total cost of installing heat pumps in every home, generating the electricity to power them and upgrading the grid to deliver that energy is approaching £300 billion.

That’s ten times more!

A national green gas programme will also involve zero hassle, upheaval and waste because all we’re actually doing is replacing fossil gas in the existing grid with green gas. It will create almost 100,000 jobs in the rural economy and create vast wildlife habitats into the bargain.

Find out more about our Save Our Boilers! campaign
We want the government to realise that stripping out functioning boilers all over the country is not the way to tackle climate change. It costs an extortionate amount of money and creates mountains of waste.

The better approach is to use existing kit in a much greener way, replacing fossil fuel gas with carbon-neutral green gas on a national scale, using proven gas generating technology.

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