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A team of researchers from Israel’s Ben Gurion University of the Negev (BGU) has demonstrated, for the first time, a technique for converting human excrement into hydrochar—a safe, renewable biomass fuel that resembles charcoal—as well as a nutrient-rich fertilizer.
According to the team, this process could potentially address two major issues that affect many less-affluent countries—poor sanitation and growing energy needs.
While access to waste treatment worldwide has improved significantly in recent years, approximately 2.3 billion people still lack basic sanitation services, according to the World Health Organization. Of those, around 892 million people—most of whom live in rural areas—defecate in the open.
“Human excreta are considered hazardous due to their potential to transmit disease,” Amit Gross, from the Department of Environmental Hydrology and Microbiology at BGU, said 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 reused properly.”
Energy scarcity is also a problem in these regions: Approximately 2 billion people worldwide use solid biomass—such as wood—which is converted into charcoal and then used for cooking and heating. However, these practices have a significant impact on the environment, contributing to air pollution, greenhouse gas emissions, deforestation and soil erosion.
“By treating human waste properly, we can address both of these issues at once,” Gross said.
In a pilot study published in the Journal of Cleaner Production, the researchers described how they used a technique known as “hydrothermal carbonization” to heat raw solid human waste in a special “pressure cooker” to three different temperatures (180, 210 and 240 degrees Celsius) for periods of either 30, 60 or 120 minutes.
This sterilizes the human waste and dries it out, creating a solid coal-like substance known as hydrochar, which can be used for household cooking and heating. In addition, a nutrient-rich liquid is produced that could be used as a fertilizer. Last year, the BGU researchers carried out similar research using poultry excrement.