Sewage Sludge to Energy - A Simulation Study

Abstract

The global shortage of resources and the intention to reduce CO2 emissions from fossil sources has triggered new approaches in the wastewater industry. Better ways are sought for to manage sewage sludge and to exploit its value as a secondary resource. However, we see a lack of tools to assess the appropriate treatment strategy which leads to imperfect process choices and designs. Here we present (a) a modeling approach and a simulation tool that allows the systematic evaluation of different sewage sludge treatment options and (b) a test case study for a mid-sized waste water treatment plant. The sludge model is discussed and tested for consistency with alternative approaches. In the case study, the direct conversion to electricity in a Rankine cycle is shown to be superior to biogas production or dried sludge export based on an energy cost analysis. The development presented is believed to enable more efficient waste-to-energy conversion and to contribute to sustainable resource management.