Lactic Acid Fermentation of Human Excreta for Agricultural Application

Human excreta is a valuable fertilizer for improving soil quality and crop productivity, with a potential to replace or complement the mineral fertilizers. The main challenges related to human excreta regarding agricultural applications are microbial contamination risks, loss of nutrients, and odor issues. Fertilization by lacto-fermented faeces supplemented by biochar has benefits such as improved soil bulk density, nitrate and potassium concentrations as well as the yield and yield components of corn, compared to untreated, simple stored faeces, urine, cattle manure, and unfertilized controls. Even though the mineral fertilizer produced corn with significantly higher height and leaf length, it did not add significantly higher yields than lacto-fermented faeces supplemented by biochar. A faeces treatment process by combined lacto-fermentation with thermophilic composting and biochar supplementation had better reduction of coliforms, Escherichia coli, Enterococcus faecalis and Clostridium perfringens, and higher germination of radish and growth of tomatoes than combined lacto-fermentation with vermicomposting. Urine lacto-fermentation contributed to a pH reduction below 4, a decrease in the ammonium concentration and odor strength, as well as an increase in the germination rates compared to untreated stored urine. The results of this study provide important information that can set the basis for scaling up a sustainable technology for the treatment of source separated human excreta while improving its potential for resource recovery.

Nadejda Andreev was born in 1972. She obtained her Bachelor of Science in Biology from Moldova State University, Faculty of Biology and Soil Sciences in 1994, and her MSc degree in 1998 at the Central European University in Environmental Sciences and Policy and also obtained a second MSc degree in Biodiversity at Swedish University of Agricultural Sciences in 2004. Dadejda is currently employed as a Leading Researcher in the Laboratory of Hydrobiology and Ecotoxicology, Institute of Zoology, Academy of Sciences of Moldova, and leads an NGO which implements projects related to decentralized sustainable technologies including sustainable sanitation.

She carried out her PhD studies at UNESCO-IHE Institute for Water Education, (Delft, the Netherlands) between 2011 and 2016. Her research interests include eco-friendly and cost effective treatment and reuse of human excreta, especially in agricultural applications. Nadejda’s PhD research topic focusses on terra preta sanitation and its applications in agriculture and urine diverting dry toilets.