Safe retrieval of nutrients to improve food security

Abstract: Safe retrieval of nutrients from human excreta to fertilize crops in order to gain adequate yields will increase food security and sustainability in agriculture areas with nutrient-poor fields. Safe and nutritious food will meet the dietary needs of the individual which promotes public health and the ability of an active life. Human excreta should be considered as a resource instead of being assumed as waste. Human faeces and urine is excellent fertilizers which may close the nutrient loop if utilized properly. However, sanitation of the excreta is required to prevent disease transmission by reducing the content of gastrointestinal pathogens such as bacteria, viruses and parasites. The objective of this study was to in small scale evaluate the sanitation in a combined liquid compost and urea treatment by monitor the inactivation of bacteria and viruses at the combination three start temperatures, 45, 40 and 35 °C, and three additions of urea, 0.5, 0.75 and 1 % and reference, 0 % urea addition. A inoculate buffered to pH 9 was used as an additional reference. Urea was added to already composted material and from the start of the treatment temperature was decreased 1 °C per day. The microbial reduction of Enterococcus spp., thermotolerant coliform bacteria, salmonella and coliphages was monitored by plate count methods together with pH and TAN. Urea addition resulted in an increase in pH and TAN and caused inactivation of various degrees among the different temperature and urea addition treatments. To obtain a sufficient inactivation of bacteria within a week of treatment the excreta has to be treated with at least 0.5 % urea and at least 40 °C initial temperature.