Repurposing waste as a valuable resource stream is a key step toward building a sustainable circular economy. Researchers from KAUST are rethinking one major component of today’s municipal and industrial waste by taking inspiration from flies. 

Where we see organic waste such as food scraps as garbage, flies sense the perfect meal. In their larval stage, black soldier flies (BSF) devour organic matter to build up the stores of proteins, fats and chitin they need to metamorphose into adult flies. In the process, the larvae — and the waste — are transformed. 

“Over a 12-day period after they hatch, the BSF larvae grow to around 10,000 percent of their original weight as they metabolize the nutrients in organic waste,” says Ribhu Gautam, a postdoc in the labs of Mani Sarathy, who led the project. “At the same time, they reduce the volume of waste significantly,” he adds.   

The fattened larvae and the remaining waste are valuable products, the former as protein-rich animal feed and the latter as high-quality organic fertilizer. “The process is rapid and generates considerably lower carbon emissions compared to any existing technology for processing this waste, including incineration, anaerobic digestion and landfilling,” says Baqer Aljaman, a Ph.D. student in Sarathy’s group. Aljaman is also CEO of Organic Waste Management Solutions (OWMS), the startup launched by the team to scale up and commercialize the BSF-based process.   

A project based on fly larvae may seem an unlikely fit for a group with a core focus on fuel combustion and pyrolysis chemistry, Gautam admits. “Our team started exploring BSF larvae in 2017, when a leading BSF company based in South Africa asked us to develop a technology to valorize the fat extracted from BSF larvae before they are fed to fish and poultry,” Sarathy explains. “We developed technologies for converting BSF fat into fuels and lubricant oils.” 

The team revisited BSF waste processing after being approached by the Tanmiah Food Company in 2020 to develop a solution for poultry farm manure and broiler waste. Sarathy is a leading expert in a process called pyrolysis, which can convert organic waste into valuable biofuels and other products by heating it in the absence of oxygen. Chicken manure, however, is not directly suitable for pyrolysis due to its high nitrogen and fat content. 

“We decided to use BSF larvae to first eat the nitrogen and fats in the manure,” Sarathy says. “The remaining waste can be pyrolyzed to produce a high-value biochar.” The larvae grown on the poultry farm waste could be separated and processed to extract high-value chemicals. 

The team has now brought on a partner, Daniel Enebeli of BSF farming startup Protein Kapital, to implement an innovative process for producing and growing BSF larvae. “Together we are applying a patented method for producing thousands of eggs per fly, instead of the 50 or so eggs they typically produce,” Aljaman says. Based on this efficiency gain, the team is now pursuing wider application of BSF technology to other organic wastes.   

“These innovations have enabled us to deploy the solution more broadly to more types of organic waste streams in Saudi Arabia,” Sarathy says. The OWMS team is developing a module-based BSF waste management process that can be set up on site where the waste is produced to aid waste management and minimize waste transportation. 

The team’s small scale demonstrator module has already processed several tons of waste in this way. “We are now scaling up to handle three tons of food waste per day,” Gautam says. The team is already in talks with several companies interested in adopting the technology. 

For Sarathy, exploring bio-based solutions to organic waste management has brought a new set of challenges, compared to the chemical approach more usually employed in CCRC projects. “We have found that BSF are remarkable creations of nature, and we focus on maintaining a healthy environment for them to devour waste while creating value,” he says.