The old saying goes that you shouldn't let the grass grow under your feet, but a British green energy company sees that neglected greenery as the solution to the UK's energy needs. Ecotricity has announced plans to produce methane using grass harvested from marginal farmland that could one day heat 97 percent of British homes and create a whole new energy industry.

Biofuels is one of those green energy solutions that sound promising, but keeps getting bogged down in the details. Animal waste might work, but how to collect it? Old frying oil could do, but are there enough chip shops? And energy crops, like maize, run the risk of turning needed food into fuel.

Ecotricity's answer is to turn grass into methane the same way as a cow does, but without the cow. In this way, the company hopes to produce a carbon-neutral source of gas that has a readily available source, fits in with the existing infrastructure, and is easily scalable.

The idea is to use marginal farm land as opposed to lawn clippings or grass collected from verges, which aren't economical. Instead, grass would be grown on land that isn't ideal for farming or as a rotation crop with others, like wheat or rapeseed. The grass would be grown, harvested, and transported to production centers called "Green Gas Mills" like any other crop, where it would be stored and turned into silage just like animal feed.

The difference is that instead of being fed to cattle or sheep, the silage is placed in large digester vats where bacteria feed on the plant matter in the absence of oxygen in a process called anaerobic digestion. According to Ecotricity founder Dale Vince, it's a well known process that differs here because it's on a larger scale and the gas collected from the vats is scrubbed of carbon dioxide and other impurities, so it can be fed directly into municipal gas lines servicing homes.

Vince says there's enough marginal land available for cultivating grass to supply the 5,000 Green Gas Mills needed across the country to heat almost all of Britain's homes. In addition, Vince claims that by growing grass using the waste product from the Mills as fertilizer, the process will actually enrich the farm land. In addition, the grass will act as a refuge for wildlife, and act as a source of income for farmers facing the loss of EU subsidies in the face of Brexit.

Vince concedes the grass gas is more expensive than conventional sources, but that might change as economies of scale take hold. In October, Ecotricity was awarded planning permission to build its first pilot plant at Sparsholt College in Hampshire, which will heat 4,000 homes.

"As North Sea reserves run out, the big question is where we're going to get our gas from next," says Vince. "The government thinks fracking is the answer, but this new report shows that we have a better option. Recently, it's become possible to make green gas and put it into the grid, in the same way we've been doing with green electricity for the last two decades. The current way of doing that is through energy crops and food waste – but both have their drawbacks. Through our research, we've found that using grass is a better alternative, and has none of the drawbacks of energy crops, food waste or fracking – in fact, it has no drawbacks at all."

The video below explains the grass to gas project.

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