Open access publications in the SLU publication database

Abstract

Source separating wastewater systems are often motivated by their integration with farming. It is thus important to scrutinise the critical factors associated with such integration. This was achieved in this work using a life cycle perspective and qualitative interviews. The objective of the thesis was to examine the environmental performance of systems integrating crop production and wastewater management in urban and rural areas. The focus was on comparisons between source separating and conventional systems using a life cycle approach. Critical factors for beneficial recycling and use of source separated sewage products as fertilisers were also investigated. Source separation of urine or blackwater with subsequent use in crop production proved most beneficial in locations where the eutrophying emissions were critical. For Swedish conditions, such separation techniques were particularly interesting as complement for on-site systems. The life cycle studies highlighted the importance of a high substitution rate when sewage products replaced mineral fertiliser in crop production. Plant nutrient availability and the fertilisation strategy employed at farm level are important factors to consider in this regard. A carefully constructed system for separation and collection and choice of sanitisation method also proved important. It was demonstrated that resource aspects associated with recycling systems are far more than a matter of plant nutrient recovery rate, since different activities required for the recycling might be associated with considerable use of energy and other resources. Methods for weighting abiotic resources are therefore needed. There are varying motives, roles and responsibility for actors involved in existing recycling schemes. The results stress the importance of local authorities and farmers devising strategies for better long-term utilisation of the nutrients in source separated sewage products. Providing arenas for participation, exchange and learning is recommended for continued development of recycling systems.