Integrating Life-Cycle Perspectives and Spatial Dimensions of Sewage Sludge Mono-Incineration

David Wagner,Florian Kretschmer,Georg Neugebauer,Gernot Stoeglehner

doi:10.3390/w12051267

David Wagner, Florian Kretschmer + Show 2 more

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https://doi.org/10.3390/w12051267

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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.

Highlights

In many countries across the world, discussions on the future perspectives of sewage sludge disposal have recently been gaining momentum [1]
Based on the presented approach and the case study in Austria, it can be concluded that sustainable sewage sludge treatment should optimize the processes of mono-incineration with in the wastewater treatment infrastructure and take the possibility to deliver energy to the surrounding spatial urban fabric into consideration
Holistic approach that combines elements of life-cycle assessment, integrated spatial and energy planning, and multiple-criteria analysis, valuable insights for the planning of resource recovery processes with regards to energy and materials can be generated that go beyond the question if central or decentral mono-incineration is more feasible

Summary

Introduction

In many countries across the world, discussions on the future perspectives of sewage sludge disposal have recently been gaining momentum [1]. In this context, the recovery of phosphorous is a key driver [2]. The end-products of mono-incineration are incineration ash and thermal energy. With regard to wastewater based energy supply, recent studies have shown two access points at WWTPs. First, to digest sewage sludge [11,12] and, second, to recover thermal energy directly from the wastewater stream using heat pumps [5,6,13].

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