Environmental and economic analysis of management systems for biodegradable waste

The management system for solid and liquid organic waste affects the enviro nment and surrounding technical systems in several ways. In order to decrea se the environmental impact and resource use, biological waste treatment an d alternative solutions for sewage treatment are often advocated. These alt ernatives include increased agricultural use of waste residuals. To analyse whether such proposed systems indicate improvements for the environment an d its sustainability, systems analysis is a useful method The changes in en vironmental impact and resource use is not only a result of changes in wast e treatment methods, but also largely a result of changes in surrounding sy stems (energy and agriculture) caused by changes in waste management practi ces. In order to perform a systems analysis, a substance-flow simulation mo del, the organic waste research model (ORWARE), has been used. The results are evaluated by using methodology from life cycle assessment (LCA). An eco nomic analysis was also performed on three of the studied scenarios. The ma nagement system for solid organic waste and sewage in the municipality of U ppsala, Sweden, was studied. Three scenarios for different treatments of so lid waste were analysed: incineration with heat recovery, composting, and a naerobic digestion. These three scenarios included conventional sewage trea tment. A fourth scenario reviewed was anaerobic digestion of solid waste, u sing urine-separating toilets and separate handling of the urine fraction. The results are only valid for the case study and under the assumptions mad e. In this case study anaerobic digestion result in the lowest environmenta l impact of all the solid waste management systems, but is costly. Economic ally, incineration with heat recovery is the cheapest way to treat solid wa ste. Composting gives environmental advantages compared to incineration met hods, without significantly increased costs. Urine separation, which may be implemented together with any solid waste treatment, has great advantages, particularly in its low impact on the environment. However, there is a lar ge increase in acidification. (C) 2000 Elsevier Science B.V. All rights res erved.