The potential of waste-to-energy in reducing GHG emissions

133 ISSN 1758-3004 10.4155/CMT.12.11 © 2012 Future Science Ltd Background Municipal solid waste (MSW) is a ubiquitous byproduct of industrialized societies. Sanitary landfills are the most commonly used means to dispose of MSW, but the limited availability of land in some places can make it difficult to find suitable locations for new landfills [1]. Additionally, in some cases, leachate produced from landfills can contaminate ground water. Current landfills are also the source of substantial GHG emissions. The US EPA estimates that 22.3% of US methane emissions in 2008 came from landfills [101]. Landfills also contain considerable unused energy in the form of MSW. Even when landfill-gas-to-energy (LFGTE) systems are used, they do not recover all of the methane produced by decomposition of the MSW. One alternative to LFGTE is the combustion of MSW to generate electricity or heat in a process commonly known as waste-to-energy (WTE). This method reduces the land requirement for waste disposal and could be a more efficient energy recovery system than LFGTE. WTE systems fit well in the concept of ‘zero waste’, along with the recycling and reuse of the MSW. WTE can also provide additional economic benefit in recovering up to 90% of ferrous materials from both waste-stream inflow and bottom-ash outflow [2]; 77% of the WTE facilities in the USA already have this capacity [3]. If WTE facilities are properly equipped with pollution control devices for flue gases, these systems can be cleaner than sanitary landfills in terms of overall environmental pollution. If CO 2 emissions from WTE plants were captured and stored underground, these plants could lead to carbon negative credits, as 66% of the carbon in MSW in the USA is typically biogenic [4–6]. WTE with CCS (WTE–CCS) is therefore one potential method to achieve carbon negative footprints [2,7]. In fact, Kaplan et al. estimate that in the USA the potential capacity for WTE is 9.7–19 GW [102]. In contrast, the total installed US capacity in 2008 was just 2.3 GW, combusting only 6.7% of the nation’s MSW [8]. Based on the large potential for energy generation, and the opportunity that WTE provides to be carbon negative, we evaluate the electricity generation potential of WTE from MSW based on the waste streams of the Carbon Management (2012) 3(2), 133–144 The potential of waste-to-energy in reducing GHG emissions