Rapid Composting and Stabilizing of Feces–A Case Study with Pig Manure

There are still 2.4 billion people practicing open defecation around the world in 2015 according to United Nations’ statistics. Untreated human feces will not only pollute the environmental waters and soils but may also cause human deseases and even death. Accordingly, we must solve the problems of open defecation in areas without flushing toilet or sanitary sewer system. The concept of Eco-toilets has emerged. Eco-toilets should ensure hygienic functions, be environmental friendly, require little to no water and treat human feces in-situ. Besides, the design principles of eco-toilets should be well aligned with economic consideration. In this study a composting system was established to stabilize pig manure, which was used to mimic human feces. The tested system includes a composting vessel, temperature and moisture controling devices and supplying materials. Physical indicators, such as pH value, conductivity and moisture content, chemical indexes, including total Kjeldahl nitrogen, total organic carbon, and C/N ratio, and biological indicators, including germination rate, relative germination rate and fecal coliforms were monitored during each cycle of batch-type composting test. The results of this study revealed that pH value was maintained slightly alkali, C / N ratio was raised due to significant nitrogen loss, and pig manure could be stabilized under suitable moisture content and temperature in 7 days. Finally, we found that the best operational condition for batch-type composting is under 50 ℃, moisture content at 45% and with appropriate amount of seeding and bulking materials.