Margareta Lundin

A life cycle assessment based procedure for development of environmental sustainability indicators for urban water systems

Environmental sustainability is a concern and stated objective for municipalities and organisations, but is often vaguely defined and clear measurement procedures are lacking. An iterative procedure for the selection of indicators, which reflects the environmental sustainability of urban water systems, is presented. The analytical basis for selecting indicators is life cycle assessment (LCA), which provides a stringent assessment of environmental sustainability. The indicators were evaluated in Case Studies in a developed and a developing region. The iterative procedure allows refinement/replacement of indicators through Case Studies and further LCA.

Environmental assessment of supercritical water oxidation and other sewage sludge handling options.

Sustainable development relies on the eco-efficient use of all flows in society; more value created out of each resource unit. Supercritical water oxidation (SCWO) can be used for treatment of wet organic waste. The technology has been under development for over 20 years but has not yet been fully commercialized. SCWO allows for complete oxidation of all organics in sewage sludge and almost complete recovery of the inherent energy, essentially without harmful emissions. In this paper, a life-cycle assessment (LCA) of sewage sludge SCWO (Aqua-Critox) is presented and the results are compared with LCA results for other sludge handling options: agricultural use, co-incineration with municipal solid waste, incineration with subsequent phosphorus extraction (Bio-Con) and sludge fractionation with phosphorus recovery (Cambi-KREPRO). For SCWO, beneficial utilization of the heat of reaction is of crucial importance for the outcome. The electricity consumed by pumping and the nitrous oxide produced are other important parameters. The best sludge handling option from an environmental point of view depends on what aspect is considered more important in the impact assessment. Regarding global warming, the energy recovery methods perform better than agricultural use.