Researchers at Ben-Gurion University of the Negev say they have conducted a pilot study that showed that raw human excrement can potentially be converted to a safe, reusable fuel and a nutrient-rich fertilizer.
The discovery addresses two major needs of the developing world: better sanitation and environmentally friendly fuel for energy, the researchers said in a statement.
The research was published ahead of World Toilet Day, which will be marked on November 19. World Toilet Day is a day designated by the United Nations to bring attention and inspire action to the global sanitation crisis. Some 4.5 billion people, or some 60 percent of the global population, either have no toilet at home or one that doesn’t safely manage their excrement, while some 892 million practice open defecation, according to the UN.
“The impact of exposure to human faeces on this scale has a devastating impact upon public health, living and working conditions, nutrition, education and economic productivity across the world,” the UN said on its website.
The Bill and Melinda Gates Foundation has also pinpointed sanitation as a major world health issue and has set up the Reinvent the Toilet Challenge to address this problem and help deliver new kinds of sewer-less toilets that cater to the needs of people who live and work off the sanitation grid.
According to the study by the Israeli researchers, published in the Journal of Cleaner Production, researchers at the Ben-Gurion University Zuckerberg Institute for Water Research used a hydrothermal carbonization (HTC) process to heat solid human waste in a designated “pressure cooker” and managed to convert the excrement into hydrochar, a safe, reusable biomass fuel resembling charcoal.
The BGU researchers conducted similar research last year on the excrement of turkeys and other poultry.
“Human excreta are considered hazardous due to their potential to transmit disease,” said Prof. Amit Gross, the newly-appointed dean of the Zuckerberg Institute. While it is rich in organic matter, nutrients such as nitrogen, phosphorus and potassium, human waste also contains micro pollutants from pharmaceuticals, which can lead to environmental problems if not disposed or re-used properly, he said in a statement.
Energy scarcity is also a challenge in these areas. Approximately two billion people worldwide use solid biomass, especially wood, which is converted into charcoal and then used for cooking and heating. But these practices leave a footprint on the environment – air pollution, greenhouse gas emissions, deforestation and soil erosion, the statement said.
“By treating human waste properly, we can address both of these issues at once,” Gross said.
In the pilot and laboratory study, the researchers subjected the raw waste material through HTC to three temperatures (180, 210 and 240 °C) and reaction times (30, 60 and 120 minutes). The solids become dehydrated, creating the hydrochar, a combustible solid, as well as a nutrient-rich aqueous (liquid) phase.
The researchers, including doctoral candidates Reut Yahav Spitzer and Vivian Mau, also said the reaction that creates the hydrochar sterilizes the waste material, so it becomes safe to handle. The “coals” can potentially be utilized for household heating and cooking, while the liquid byproduct can be used as liquid fertilizer.
The study was funded by the Rosenzweig-Coopersmith Foundation and the Israel Water Authority.
The Zuckerberg Institute for Water Research, Israel’s largest and leading water institute, conducts interdisciplinary research and graduate education in water sciences.
Named after New York philanthropist Roy J. Zuckerberg, the institute was founded in 2002 within the Jacob Blaustein Institutes for Desert Research at the Sde Boqer Campus of Ben-Gurion University of the Negev.