Feargus O'Sullivan is a contributing writer to CityLab, covering Europe. His writing focuses on housing, gentrification and social change, infrastructure, urban policy, and national cultures. He has previously contributed to The Guardian, The Times, The Financial Times, and Next City, among other publications.
By spring 2017, the town of Keynsham could get up to 80 percent of its electricity from food waste alone
The future of green energy production might be in that bag of slimy kale in the back of your refrigerator. That’s the promise of a new power plant being built in a small U.K. town. The plant, now under construction in Keynsham, a town of 16,000 residents between Bath and Bristol, will use anaerobic digestion to generate electricity from food waste. The plan is to make enough of it to supply 80 percent of the town’s needs.
Plants like these aren’t in themselves a new idea, of course. Anaerobic digestion of sewage is common across the world. Several European countries, notably Germany, have also invested in power plants run partly on food waste, whose energy yield is generally higher than that for sewage slurry. What is potentially groundbreaking is that Keynsham’s plant, which is being built by the company Resourceful Earth, aims to be the first in a national network of small waste recycling/power production facilities designed to service individual communities. Instead of shipping expensively extracted fuels to large centralized power plants and then transmitting that electricity across long distances, this scaled-down approach uses a resource that’s locally abundant—food waste from nearby residents—and distributes the power it creates within the same area.
This so-called distributed generation model is generally more efficient and resilient than the more-common centralized generation power network, especially if, as in Keynsham, the plants consume renewable sources of energy. This combination of waste management and power generation could spin up a virtuous cycle of reduced carbon emissions, smaller landfills, less power transmission infrastructure, and cheaper electricity for residents. With a construction price of £8 million ($9.8 million), the plant isn’t even that expensive.
The technology itself is quite simple. Locally sourced food waste is digested by bacteria in an airless environment, producing methane. This methane is then captured and burned to produce electricity, a process that will begin at Keynsham in spring 2017. Prices haven’t yet been fixed or published, but the hope is that the electricity will be offered at a considerably lower rate than conventionally sourced electricity. The residue left over after the methane has been extracted—called digestate—can then be pasteurized and used as a fertilizer.
The idea of burning gas being a green solution might seem counterintuitive, but converting food to biogas via digestion is actually climate-friendlier than composting it: As it biodegrades, compost (which Resourceful Earth already makes) emits methane, which can trap a lot more heat in the atmosphere than carbon dioxide. Composting doesn’t produce extra methane: The gas would have been released anyway as the waste rotted. Capturing it and burning it releases no more carbon dioxide than the plants absorbed while growing, but methane emissions are completely eliminated.
It’s an elegant solution, but only a partial one: Even if the U.K. waste-food mountain remained as high as it is currently—around 15 million tons a year—and all this waste was used for anaerobic digestion, the total power produced would only be enough to provide power for 350,000 households. That sounds impressive, but wouldn’t go far in a country of 26.7 million households.
Still, Resourceful Earth’s plan to synchronize recycling and power production is worth watching: Rolled out nationwide, it might help the U.K. hit its carbon emissions targets—a reduction of 80 percent from 1990 levels by 2050 —without boosting energy costs.