| By Coco Liu and David Herbling For most urban dwellers, flies are a nuisance to be kept in check with screens, swatters and traps. But in the Mukuru area of Nairobi, Kenya's capital, they are being cultivated for a surprising purpose: to help tame increasingly destructive flash floods driven by climate change. Enter one fly farm, located in a church compound, and you'll be greeted by fetid odors. A peek at a nearby plastic tray reveals why: Clumps of larvae wriggle around decaying food waste. The greenhouse-like facility breeds a common species known as the black soldier fly, tens of millions of them at a time, to feed on tons of neighborhood rubbish that might otherwise choke drainage channels. "These flies are soldiers in waste management," says David Kinyanjui, 43, an operator of the experimental farm, standing next to a rack of trays. While flash flooding can occur anywhere that experiences bursts of intense rainfall, the risk in Mukuru is amplified here by heaps of garbage that block storm drains and natural waterways. Every time it rains, the trash becomes a liability. In May, when catastrophic rainfall battered the district, "there was flooding almost everywhere," Kinyanjui recalls, in part because of the clogged ditches. He spent days draining flood water out of his home. But he is lucky—the flood killed dozens of his neighbors. As climate change disrupts weather patterns, scientists say that flash floods will likely get "flashier," meaning the water level rises higher, faster. Governments worldwide are expanding and retrofitting infrastructure to withstand future flooding, but that requires time and a big budget. While advanced economies may be able to afford that kind of outlay, poorer nations such as Kenya cannot. Hence the enlisting of black soldier flies to battle garbage in Mukuru — a pilot funded by the Netherlands-based Global Center on Adaptation. For Kinyanjui, rearing black soldier flies means frequently knocking on his neighbors' doors. Twice a week, he and his 10-member crew visit alleys of corrugated iron shacks to collect organic waste. They also stop at food stands and community farms to gather more. Organic waste — an umbrella term for all biodegradable refuse — is the main culprit behind Mukuru's trash accumulation. A tray of fly larvae consume as much as 10 kilograms (22 pounds) of organic waste over the course of 14 days. As they eat, they leave behind nutrient-dense manure that can be sold as organic fertilizer. Since Russia's invasion of Ukraine drove up fertilizer prices worldwide, Kenyan farmers have been in search of more affordable alternatives. Protein-rich fly larvae can also be sold as animal feed. The farm has yet to break even since its debut in June, but Kinyanjui says he is confident that it will make a profit as the production scales. Once it reaches its full potential, it is expected to handle 6 tons of organic waste each month and yield $970 worth of fly byproducts. "This is just the beginning of the journey," says Patrick Verkooijen, chief executive officer of the Global Center on Adaptation. The group is considering replicating the Mukuru model elsewhere. Globally, more than 1 billion people — about one in four urban dwellers — live in informal settlements facing similar struggles. Mukuru's success, or failure, will "provide very important lessons, not just for Nairobi or Kenya but for the Global South in its totality to reap the benefits of working with nature, as opposed to working against it," Verkooijen says. Read the full story on Bloomberg.com — and for unlimited access to climate and energy news, please subscribe. | 
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