Recent attention in the North American market has focused on managing food waste biologically using anaerobic digestion (AD) technology, which produces a biogas that can be used to generate electricity and a digestate or residue that can be used as a fertilizer, or composted and used as a soil amendment. The increased focus on AD is driven by the desire to increase waste diversion rates and a perception that AD is a “greener” approach to managing food waste than landfilling or conventional waste-to-energy (WTE) technology. Policy makers in some cases have already concluded that AD of source separated organics is preferable to landfilling and WTE. While the environmental benefits of AD over landfilling are obvious, especially for landfill sites without active gas collection systems, the benefits are less clear when compared to conventional WTE technology since relatively little analysis has been performed to date.
Two environmental considerations often associated with being a “green technology” are energy recovery potential and greenhouse gas generation. This paper examines the amount of energy that can be produced by treating food waste biologically using AD compared to treating the same material thermally using mass burn WTE, which is the most commonly used WTE technology. The impact on net greenhouse gas emissions, namely carbon dioxide generation, from each technology is also compared taking into account a variety of factors including differences in the percentage of the feedstock carbon converted to carbon dioxide, the amount of fossil fuel avoided as a result of power generation, and the amount of vehicle emissions associated with collection and transportation of source separated food waste. This paper also compares other important considerations such as capital and operating costs, residuals management, and odor control.
