Application of Anaerobic Digestion in Decentralized Faecal Sludge Treatment Plants

Over 80% of the population in low- and middle-income countries (LMIC) depends on on-site sanitation, largely pit latrines and septic tanks. Anaerobic digestion (AD) can stabilize the organic fraction of faecal sludge (FS) while also generating biogas to offset some energy needs at the treatment plant. This chapter examined the technical and operational feasibility, as well as opportunities for AD of FS. FS that has spent long time in containment systems produces less gas than the fresh one. Therefore, FS from container-based sanitation facilities can boost gas production in biogas facilities receiving aged FS. In addition, co-digestion with different organic waste substrates improves the quantity and quality of biogas production. However, a system for transportation, pre-treatment and storage of organic feedstock for co-digestion with FS should be examined against the backdrop of cost and benefits to determine whether the improved gas production matches with the required resource inputs. In conclusion, biogas is not the only driving factor for AD. Other benefits such as organic matter stabilization and environmental benefits such as pathogen and odour reduction contribute to the driving factors for adopting AD of FS. The mineralized nutrient content in bio-slurry can be taken advantage of, although with care to avoid microbial health risks.