Waste-to-ethanol conversion is a promising technology to provide renewable transportation fuel while mitigating feedstock risks and land use conflicts. It also has the potential to reduce environmental impacts from waste management such as greenhouse gas (GHG) emissions that contribute to climate change. This paper analyzes the life cycle GHG emissions associated with a novel process for the conversion of food processing waste into ethanol (EtOH) and the co-products of compost and animal feed. Data are based on a pilot plant co-fermenting retail food waste with a sugary industrial wastewater, using a simultaneous saccharification and fermentation (SSF) process at room temperature with a grinding pretreatment. The process produced 295 L EtOH/dry t feedstock. Lifecycle GHG emissions associated with the ethanol production process were 1458 gCO(2)e/L EtOH. When the impact of avoided landfill emissions from diverting food waste to use as feedstock are considered, the process results in net negative GHG emissions and approximately 500% improvement relative to corn ethanol or gasoline production. This finding illustrates how feedstock and alternative waste disposal options have important implications in life cycle GHG results for waste-to-energy pathways. (C) 2014 Published by Elsevier Ltd.