The Unit performs both research and education, at both undergraduate and postgraduate levels. The main topic is systems and processes for safe recycling of plant nutrients from the city back to the food production, which is an essential part of a sustainable society, both in developed and developing countries. The research is based on systems analysis and process oriented. Important methods in the system analytic research is ”Substance Flow Analysis” (SFA) and ”Life Cycle Analysis” (LCA). The process oriented research is mainly focused on source separating sewage systems, sanitation/hygienisation technology, both for Swedish conditions and conditions in developing countries, and systems in the compost process.