Abstract
Pyrolysis of human feces renders the waste free of pathogens and is a potential method of treating fecal sludge waste collected from non-sewered systems. Slow pyrolysis experiments were conducted on human feces and the char yield and gas evolution quantified at 1–10 °C/min heating rates. Char yield ranged from 35.1 to 35.8% (dry mass basis), while the gas yield ranged from 17.2 to 29.6% (dry mass basis). The pyrolysis gases detected were CO, CO2, CH4, C2H6, and H2. These non-condensable gases contained a higher heating value (HHV) ranging from 7.2 to 22.8 MJ/Nm3. Kinetic analysis was done by a pyrolysis reaction model free method (Isoconversional) as well as a DAEM (Distributed Activated Energy Model) method that assumes many irreversible first order reactions. Both yielded very close values for activation energy ranging from 141 kJ/mol to 409 kJ/mol, with half of the biomass conversion happening at 241.5 ± 2.9 kJ/mol. The findings of the research provide useful technical information that can guide the design of a pyrolysis system to treat fecal waste. Social acceptance and scale-up issues need to be addressed through further research.
Highlights
40% of the global population lacks access to sanitation services and facilities in part due to the high costs of construction and materials
The purpose of the current study is to investigate the slow pyrolysis of un-treated human feces using Thermogravimetric Analysis, quantify the non-condensable pyrolysis gases released, and model the reaction kinetics
This study showed that non-condensable gases were released with an average yield of 20.9% on a mass basis for a slow pyrolysis of fresh dried feces
Summary
40% of the global population lacks access to sanitation services and facilities in part due to the high costs of construction and materials. The majority of new toilets being installed in developing countries are ventilated improved pit (VIP) latrines that do not use flush water. Consuming low amount of water for their operation, the level of treatment for pit latrine waste is very low in most low-income countries. This is especially pronounced in densely populated urban areas, where the waste material filling up pit latrines is often dumped into the environment. Development of new and improved treatment processes are needed for fecal sludge generated from latrines. Processes that can convert the fecal sludge into valuable products in addition to treatment, could create monetary incentives for communities and entrepreneurs to adopt safe sanitation practices in lowincome communities
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