Food waste-to-energy in developing countries: A case study on anaerobic digestion in a Costa Rican urban area

Municipal Solid Waste is often composed of a high share of food waste, which entails a constraint to achieving sustainable cities and food systems due to the societal, environmental, and economic challenges it represents. Therefore, many efforts are made to address the issue: waste-to-energy alternatives pose an opportunity to retain value still present in food waste and recirculate it in economic systems. This study addresses the waste-to-energy potential that anaerobic digestion represents when used to treat food waste in urban settings, using the Costa Rican Great Metropolitan Area as a case study. Our methodology provides a step-by-step guide to measure food waste and its potential by estimating food waste based on the common urban Costa Rican diet and food waste percentages, followed by the preparation of food waste samples that were treated at lab scale to estimate their biogas productivity (220 Nm3/ton): three food-group blends were analyzed, considering the composition and standard deviation of the Costa Rican diet. Finally, electric energy potential was calculated for the mixed blend (as the more likely to occur in this context, assuming 200 kWh/ton) and results were cross-referenced with local actors and experts. As a result, anaerobic digestion seems to be viable for energy production while treating food waste. However, there are several technical, logistic and political barriers that are limiting the potential of these type of alternative energy options. Other cities can take advantage of this study to begin assessing the potential of treating food waste and converting it into energy.