Environmental and economic assessment of the use of biodrying before thermal treatment of municipal solid waste

Abstract

Mass-burn incineration is a thermal treatment process for municipal solid waste (MSW) that is commonly applied worldwide. MSW can be sometimes pretreated prior to incineration to increase its calorific value. Biodrying is lately widely applied to MSW as a pretreatment process prior to incineration to produce a RDF of higher calorific value compared to raw commingled MSW. However, no information exists on the assessment of the overall environmental emissions and energy consumption of the combined biodrying-incineration process. Therefore, the goal of this work was to estimate the overall viability of biodrying prior to incineration by accounting for the greenhouse gas emissions, net energy balance and total cost. These parameters were compared to the corresponding parameters of the direct mass-incineration of MSW without any pretreatment. The study developed four scenarios that included mass-incineration alone and incineration of biodried waste. Additional scenarios were developed to include transport of waste to a distance of 100 km. Results revealed that direct mass-incineration led to slightly lower overall greenhouse gas emissions compared to incineration of biodried MSW, primarily due to the consumption of electricity during the preceding biodrying stage (because of the required aeration) and the direct emissions of biodrying. In addition, a 5% less overall energy consumption was calculated during mass-incineration, compared to incineration of biodried RDF, while the net cost was also lower in the case of the mass-incineration compared to the RDF based incineration.

Keywords: Biodrying; Greenhouse gas emissions; Incineration; Mass balance; Mass-burn; RDF.