Integrating life-cycle perspectives and spatial dimensions of sewage sludge mono-incineration

Abstract

The mono-incineration of sewage sludge offers new opportunities to develop wastewater infrastructure as regional energy cells and resource recovery sites. At the moment, the most important products of this technology are electric energy and heat from combined heat and power plants, as well as ash for the recovery of phosphorus. With spatial analysis, scenarios of the decentralized and centralized spatial organization of mono-incineration are assessed with regard to the energy balances of the incineration process, transport demands, and the possibility to accommodate excess heat in the surrounding spatial fabric, and these are evaluated by applying a multi-criteria analysis. The study is based on the Austrian case and shows that the utilization, not only of phosphorus and excess energy but also of other potential resources should be aimed for. The transport of sludge and the potential to use excess heat in the surrounding spatial fabric decide if centralized or decentralized scenarios are environmentally more feasible, whereas an "economy of scale" clearly gives leeway to the centralized options. Therefore, this study clearly demonstrates that introducing mono-incineration should not only focus on the process engineering itself but should also consider spatial planning provisions to reduce transport demands and to deliver excess energy to the surrounding spatial fabric.