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This British Supermarket Will Be Powered Entirely by Its Own Food Waste

A Sainsbury's store has gone off-grid thanks to the energy produced from the chain's food waste through anaerobic digestion.
Image: Shutterstock/Xavier MARCHANT

A supermarket chain in the UK announced today that it’s going to power one of its stores entirely off food waste. It’s an attractive solution to two of the most gnawing sustainability concerns: waste and energy.

A Sainsbury’s in Cannock, a town in the West Midlands, will get all of its electricity from food waste through a process called anaerobic digestion. The process is pretty much what it sounds like: waste food is “digested” by microorganisms in huge tankers sealed off from the air, which Sainsbury’s compares to a human stomach. Biffa, the waste management company working with the supermarket, explains that the waste is broken down into a slurry that degrades into an energy rich biogas, a mixture of methane and carbon dioxide.

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Those two aren’t particularly desirable—they’re greenhouse gases—but a site run by bioenergy consultants NNFCC explains that their production is offset by the fossil fuels they go on to replace when they’re turned into energy, and adds that if the same food waste went to landfill, it would rot and release methane anyway.

In the Sainsbury’s case, that biogas will be turned into biomethane at Biffa’s anaerobic digestion plant in Cannock by removing other gases. That’s turned into electricity and sent along a new 1.5km cable to power the supermarket’s lighting, refrigerators, and so on, without the need for fossil fuels. Any surplus goes back into the national grid.

The supermarket was actually already the largest retail user of anaerobic digestion in the UK, and the waste process is growing rapidly; government-funded sustainability organisation WRAP told me that there are currently 60 anerobic digestion sites in the UK, while 15 years ago there were none. But Sainsbury's plan to use the generated electricity to directly and solely power one of their stores, taking it off-grid, is a nice demo of the recycling feedback loop. It’s the first business to put such a linkup into practice. It will only send food waste that’s unsuitable to be donated to charity or turned into animal feed to the processing plant.

There is a byproduct—the creation of the biogas leaves behind a digestate—but that’s full of nutrients and can be used as a biofertiliser for agriculture. Win-win.

Sainsbury’s hasn’t revealed how much waste food is used in the process and exactly how much energy it produces (a request for comment was unanswered at time of press), but from their announcement it seems like there’s limited opportunity to power more stores this way. The company explains that Biffa picks up food waste not only from the Cannock store but also from their supermarkets across the UK to be digested at the plant; you need a fair amount of waste to power just one store.

Of course, a lack of waste is a good thing—it’s surely still preferable to limit the amount of food that goes to waste in the first place, even if you have a way to recycle it. Biffa’s anaerobic digestion plant is licensed to process up to 120,000 tonnes a year.

The amount of energy produced depends on both the kind of waste you put in and the type of digester you use, but the NNFCC site states that one tonne can generate around 300kWh. The UK government says that anaerobic digestion is the “best environmental option currently available” for food waste that can’t be avoided, and the Renewable Energy Association reckons that if the entire country’s domestic food waste was recycled using anaerobic digestion, it could power 350,000 households. Put another way, WRAP said that a typical household's food waste for a year could power their home for four days.

That might not make it particularly reliable as an energy source, but it's still an extra environmental, and potentially economical, advantage to the waste solution. And certainly a lot better than continuing to blindly pile up landfills and pump out fossil fuels.