Bench-scale composting of source-separated human faeces for sanitation

In urine-diverting toilets, urine and faeces are collected separately so that nutrient content can be recycled unmixed. Faeces should be sanitised before use in agriculture fields due to the presence of possible enteric pathogens. Composting of human faeces with food waste was evaluated as a possible method for this treatment. Temperatures were monitored in three 78-L wooden compost reactors fed with faeces-to-food waste substrates (F:FW) in wet weight ratios of 1:0, 3:1 and 1:1, which were observed for approximately 20 days. To achieve temperatures higher than 15 °C above ambient, insulation was required for the reactors. Use of 25-mm thick styrofoam insulation around the entire exterior of the compost reactors and turning of the compost twice a week resulted in sanitising temperatures (⩾50 °C) to be maintained for 8 days in the F:FW = 1:1 compost and for 4 days in the F:FW = 3:1 compost. In these composts, a reduction of >3log10 for E. coli and >4log10 for Enterococcus spp. was achieved. The F:FW = 1:0 compost, which did not maintain ⩾50 °C for a sufficiently long period, was not sanitised, as the counts of E. coli and Enterococcus spp. increased between days 11 and 15. This research provides useful information on the design and operation of family-size compost units for the treatment of source-separated faeces and starchy food residues, most likely available amongst the less affluent rural/urban society in Uganda.