See: https://www.ecotricity.co.uk/our-green-energy/our-green-gas

The basic idea is three steps:

• Grow "grass" (like what's on your lawn) on a few acres of land, which can be marginal land.
• Harvest the grass from time to time, putting it into a biodigesting processing system.
• Clean up the resulting methane gas, supplying it to the electricity grid, and using other byproducts for other means including fertilizing the land.

From: https://www.ecotricity.co.uk/news/news-archive/2016/ecotricity-s-green-gasmill-at-sparsholt-college-gets-go-ahead

Ecotricity’s Green Gasmill at Sparsholt College gets go-ahead

13 October 2016

Ecotricity, Britain’s leading green energy company, has today received planning permission to build a Green Gasmill in Hampshire – the first of its kind in Britain.

Located at Sparsholt College in Hampshire and fuelled by locally sourced grass, the Green Gasmill will inject £60 million into the local economy, create new jobs, and produce enough clean gas to heat over 4,000 homes every year.

As part of the unique partnership, Ecotricity will finance and build the Green Gasmill with an investment of £10 million, and also help fund the development of a Renewable Energy Demonstration Centre.

The College has agreed funding of £1.2m in grant funding from the Local Enterprise Partnership (M3 LEP) to go towards the development of the College’s Renewable Energy Demonstration Centre.

The Renewable Energy Demonstration Centre will also be the first of its kind – a place to train the next generation of green energy engineers in Britain.

Ecotricity introduced the concept of making green gas from grass in Britain early last year, and after today’s planning permission from Winchester City Council, it will be full speed ahead to complete the necessary preparation before construction can begin.

Dale Vince, Ecotricity founder, said: “This is great news, green gas from grass has so much to offer Britain, and this planning consent gives us the opportunity to get started.

“Earlier this week the government overruled the local planners in Lancashire to grant approval for the first Fracking site in Britain - as opinion polls show opposition to Fracking reaching an all-time high.

“Green gas is the answer, Hampshire looks set to lead the way.”

Tim Jackson, Sparsholt College principal, said: “I had every confidence that the planning committee would see the logic of this application which is entirely in line with local and national planning policy.

“The low carbon aspirations of Winchester through their Low Carbon Strategy are commendable but ambitious, and it needs projects like this one at Sparsholt College to help the 20% target of energy generated from renewables by 2020 in order to stand any chance of meeting this.

“I'm confident that working with Ecotricity, the College will be able to allay the many unfounded concerns that have been raised during the Planning Application process, and ensure that the project both delivers strongly on its outcomes without inconvenience to those living nearby or further afield.

“I'm also delighted that this project has been so well supported by Grant Funding from the Enterprise M3 LEP and look forward to working with Ecotricity on the delivery of the project.

“It’s good for developing the learning and skills of our current agricultural students and also for developing skills for the future of the industry. It’s also a really significant low carbon energy project for the Winchester area, and in the wider public interest.”

The original planning application for the site was refused in April of this year, however instead of appealing the proposal, Ecotricity addressed the transport concerns in a fresh application, which was submitted in July and included significant traffic alterations and new information.

The company also consulted representatives of the nearby parish councils and incorporated their requests, wherever possible into the routing plans and operational controls.

The resubmission included new and revised traffic data and assessment, new traffic plans to keep vehicle movements away from Sparsholt village and a commitment to protect local road infrastructure.