Climate variability and food waste treatment: Analysis for bioenergy sustainability

Although reducing food waste is essential for the necessary reduction in greenhouse gas (GHG) emissions for climate mitigation, not all food waste is avoidable. Currently, food waste is mainly disposed of in landfills in low-income countries, whereas some industrialized countries in Asia recycle a majority of their food waste as animal feed or compost. The present study therefore investigates the large-scale implementation of technological alternatives for the valorization of food waste into biogas and bioethanol. First, a projected scenario of global food waste in 2050 is provided using a data-driven model that takes into account spatial differences in the types of food waste at the country level. This scenario indicates that food-waste-related GHG emissions alone nearly reach the 2 °C target emissions allowance. Next, the food-waste-to-biogas and food-waste-to-bioethanol pathways, including the upgrading of food waste-derived acetic acid to bioethanol, are examined via large-scale modeling and analysis to estimate their potential for bioenergy production and their resulting GHG footprint. Finally, a national-scale optimization of climate mitigation benefits under alternative conversion pathways (bioethanol versus biogas) is performed. This optimal scenario indicates that the production of bioethanol using one half of all the food waste generated by the four largest waste-producing countries (China, USA, India, and Brazil) can generate 31.9–34.0 × 1018 J (or 31.9–34.0 EJ (EJ)) of renewable energy and decrease GHG emissions by 22.8–26.8 Gt CO2 eq. Furthermore, the catalytic conversion of food waste to bioethanol can potentially maximize climate mitigation to 4.0–4.8 trillion USD while preventing a 0.06–0.07 °C increase in global mean temperature change in the cumulative period of 2011–2050.