Sewage sludge handling with phosphorus utilization – life cycle assessment of four alternatives

Four handling options for sewage sludge were studied from an environmental systemʹs perspective using life cycle assessment. The studied options were restoration of mining areas, composting with other biomaterials for use on golf courses, hygienisation through storage for agricultural use, and supercritical water oxidation with phosphorus recovery. The results are discussed in terms of impact on global warming, acidification, eutrophication, and the use of finite resources and primary energy. A very large impact of including biogeochemical emissions from sludge handling and spreading on land can be seen. System expansions for replaced artificial fertilizers also had a major influence on the results. It is clear that it is important for the environmental outcome of sludge treatment options that biogeochemical emissions from sludge are minimized and that nutrients and other resources are utilized efficiently.