Scientists claim to have shown that human waste can be used as a fuel safely, which could make it a viable source of fuel in certain countries.
Published in the Journal of Cleaner Production, the study was led by the Ben-Gurion University of the Negev (BGU) in Israel. Using a pressure cooker, the team said they were able to convert excrement into hydrochar, a safe and reusable biomass fuel that resembles charcoal.
“Human excreta are considered hazardous due to their potential to transmit disease," said study co-author Professor Amit Gross from BGU in a statement. “While it is rich in organic matter, nutrients such as nitrogen, phosphorus and potassium, human waste also contains micropollutants from pharmaceuticals, which can lead to environmental problems if not disposed or re-used properly.”
In their study, the team used hydrothermal carbonization (HTC) to heat the waste to up to 240°C (460°F) for up to two hours. This caused the waste to become dehydrated, producing hydrochar, which is both combustible and nutrient-rich, meaning it can be used as fuel and fertilizer. The process also sterilizes the hydrochar, making it safe to handle.
About 2.3 billion people in the world lack basic sanitation, which includes 892 million people that defecate in the open. Some of these regions also have to deal with a scarcity of energy.
Many use solid biomass like wood, converted into charcoal, for cooking and heating. However, these have a significant carbon footprint, whereas human waste could offer a cleaner alternative. In theory, hydrochar could be used to heat homes and in cooking, with its liquid byproduct useful as a fertilizer.
"By treating human waste properly, we can address both of these issues [energy and waste] at once," Professor Gross said.
Similar research was conducted by BGU last year on the excrement of turkey and other poultry. The team found the best results came from cooking the feces while it was wet at high temperature and high pressure, like in a pressure cooker.
“Their ultimate goal is to try to roast a bird with their homemade hydrochar, and eat it afterwards,” noted NPR. “Once made, the hydrochar doesn't emit any stink – it even has a pleasant aroma!”