The British supermarket Waitrose has a bone to pick with food waste . Five years ago, Waitrose stopped sending food waste to landfills; now, it turns any food that can’t be donated into electricity (Sainsbury’s, another U.K. chain, also turns waste into power ). The stores started selling a line of misshapen produce , marketed with messages about food waste, in 2016. Now, the supermarket’s new delivery trucks will be powered by fuel made from food scraps.

Gas made from food waste is cheaper than diesel, which is used in most heavy-duty trucks. It also emits about 70% less carbon dioxide. Waitrose’s 10 new eco-friendly delivery trucks can run for up to 500 miles on the food-based fuel.

“Waitrose has been spending the last seven to eight years looking at ways they can clean up their transport,” says Philip Fjeld, CEO of CNG Fuels, which partnered with the supermarket on the switch, and which operates the fueling stations. “They’ve looked at biodiesel, they’ve looked at electric, they’ve looked at all kinds of renewable fuels,” he tells Co.Exist in an interview.

Biodiesel fuel is expensive; fully electric trucks face challenges with the weight of the batteries and the time needed to recharge (unlike a city bus, which can charge while it sits in a garage overnight, large trucks are often on the road for much longer hours).

Fuel made from food waste, on the other hand, is about 35-40% less expensive than diesel. While the trucks that can use it cost about 50% more upfront than a normal diesel truck, the extra cost can be offset with two or three years of cheaper fuel; over the lifetime of a truck, the supermarket could save more than $100,000. The trucks can also refuel within five minutes.

The trucks don’t run directly on rotting food. Anaerobic digestion plants capture biomethane from the food waste, and that gas goes into the national gas grid. At fueling stations, CNG Fuels pulls gas from the grid, compresses it, and then tracks how much fuel goes into the truck, so it can buy the exact equivalent amount of biomethane and issue Waitrose a certificate for renewable fuel.

A handful of other companies are also beginning to use the new fuel, and there’s enough for more to do so. “As of today, there is sufficient biomethane or renewable gas from food waste to fuel thousands of trucks–I would say somewhere between 2,000 and 5,000 trucks,” says Fjeld. While that’s only a fraction of the heavy duty trucks on U.K. roads, there is (unfortunately) enough food waste that production can be scaled up in the future.