The British chain Waitrose — similar in scale and vibe to the U.S. chain Whole Foods — has partnered with CNG Fuels, a European provider of renewable biomethane gas. CNG stands for compressed natural gas, although in this case the natural gas is biomethane that’s derived entirely from food waste.

On average, biomethane is 35 to 40 percent cheaper than traditional diesel fuel and emits 70 percent less carbon dioxide, according to numbers from CNG Fuels. It’s a fundamentally different system than biodiesel or liquefied natural gas, and potentially much more cost effective.

So why isn’t everyone fueling up with compressed biomethane? Well, trucks with the modified engines are more expensive, for one thing. Also, there is the matter of infrastructure — biomethane gas stations can be tricky to find.