Anaerobic digestion of undiluted simulant human excreta for sanitation and energy recovery in less-developed countries

Improving access to sanitation is one of the most effective means to improve public health. Anaerobic digestion of high-strength undiluted human simulant excreta was investigated in laboratory systems. The focus was on demonstrating the suitability of using simple unmixed anaerobic digesters for the treatment of a simulant high-strength undiluted human excreta and to quantify the effects of high ammonia concentration on the biogas yield. A maximum biogas yield of 0.44 NLbiogas g(COD)(-1) was obtained in batch experiments, while yields of 038 and 0.24 NLbiogas g(COD)(-1) were obtained at 5 and 8 g total ammonia nitrogen (TAN) L-1, respectively. Using an inoculum acclimated to high ammonia concentrations was critical to successful biogas production at these high TAN concentrations. Stable long-term anaerobic digestion of simulant human excreta at ammonia concentrations ranging from 5.20 to 7.15 g-N L-1 was obtained in a scaled-down mimic of a low cost floating dome anaerobic digester. Overall, the results demonstrate that anaerobic digestion of undiluted human simulant excreta in simple unmixed digesters is feasible and yields biogas, which is a valuable commodity. When combined with proper hygienization of its effluent, anaerobic digestion could contribute to effective sanitation in developing countries with limited water availability. (C) 2015 The Authors. Published by Elsevier Inc. on behalf of International Energy Initiative.