Assessing the value of fertilisers derived from container-based sanitation systems

Abstract

It is estimated that 61% of the world population lacks access to safely managed sanitation and that in low-income countries (LICs) only 6.7% of the population is connected to a sewerage network. Container-based sanitation (CBS) systems have shown great potential for increasing access to sanitation in densely populated urban slums given that they do not require permanent infrastructures. Resource recovery is usually an essential part of CBS systems to provide sustainable faecal sludge management. Transforming human excreta into fertilisers creates value from faecal sludge while producing an organic soil amendment, addressing both sanitation and soil fertility challenges. Soil amendments made from organic residues are however known to be difficult to market profitably. This thesis therefore investigated the properties of human excreta derived fertilisers (HEDF) and the opportunities and challenges to their commercialisation in LIC. Nutrient characterisation of composts, anaerobic digestate and vermicompost from two CBS ventures showed significant differences in nutrient content between these three HEDF types. Pathogen and heavy metal analyses demonstrated that there is no pollution threat from HEDF when produced according toWHO guidelines. Field and glasshouse crop trials demonstrated the positive effect HEDF can have on crops and soil health. These benefits however do not currently translate into their commercial value. A case study approach was used to identify barriers and enabling conditions faced by two CBS organisations that successfully produce and sell HEDF. The low market value of compost prevented both organisations from recovering treatment costs from HEDF sales. One major barrier to wider adoption of HEDF use was the lack of regulations or certifications specific to this type of fertiliser. Perception challenges exist because of the potentially harmful components human excreta contain such as pathogens and heavy metals. It is therefore essential to create a way of proving or guaranteeing the quality and safety of HEDF products. The value of qualityassuring schemes for HEDF became evident when applying the Biosolids Assurance Scheme from the UK to HEDF, which helped identify a contamination issue in one of the treatment sites considered.