Characterizing Properties of Biochar Produced from Simulated Human Feces and Its Potential Applications

This study presents a comprehensive characterization of biochar obtained from simulated human feces (SHF) with a view to improve human waste sanitization and stabilization before usage as a resource. The possible applications of SHF are as a fuel, as a soil amendment, or for emerging applications (e.g., activated carbon precursor and odor control), depending on the charring conditions. Simulated human feces were charred under different conditions of peak temperature (200-800°C), heating rate (2-50°C min), and holding time (0.5-6.0 h); these parameters have been shown to have the largest influence on the thermal and physicochemical characteristics of the final product. The peak temperature was shown to have a higher impact than the heating rate or the holding time. At 200°C, the very mild structural changes of the product were characteristic of dry torrefaction, a process useful to remove moisture and sterilize the product. At 400°C the carbon content (76.2 ± 0.4) and the calorific heat value (30.6 ± 0.4 MJ kg) of the product increased by 60%. From 600°C onward, the improved degree of aromatization verified by Fourier transform infrared spectrometry (alkene [C=C] stretching around 1680-1450 cm) and C nuclear magnetic resonance (C=C stretching at 140-110 ppm) made the biochar increasingly suitable for carbon sequestration or commercial fabrication of briquettes of charcoal. In conclusion, SHF proved to be a suitable feedstock to produce a biochar whose characteristics depended mostly on the peak charring temperature. Ultimately, the selection of a suitable application may depend on local and sociological considerations.