Comparison of Batch CSTR Leaching and Biodegradation of Autoclaved and Not Autoclaved Human Feces with Regard to Recovery of Major Inorganic Crop Nutrients

Bioprocessing of human fecal wastes may be an important means for recycling of crop nutrients within a closed Advanced Life Support System. The objectives of this study were to determine the levels of key crop nutrients that can be extracted from human feces that had been autoclave sterilized vs. those that had not. When compared with inedible ALS grown wheat residues, the contribution of feces, which has an ash content 13% to the total potential, recoverable minerals may be small. This paper discusses results from bioreactor runs obtained using continuous stirred tank reactors with an 8 day batch culture of autoclaved or not autoclaved feces. The results suggest that feces should not be autoclaved if mineral recovery is desired. Biodegradation of feces ranged from 27 to 39% in 8 days, with 67 to 79% reduction in soluble total organic carbon (TOC) and concomitant production of carbon dioxide (CO₂).