Thermochemical Conversion As a Sustainable Food Waste Management Strategy

Food waste has recently emerged as a major sustainability issue on a global scale, with 30-40% of food produced never being consumed by humans. Because of the associated environmental and economic impacts, many regions have implemented organics landfill bans that prevent landfill disposal of food waste, especially for relatively large generators such as food processing plants, grocery stores, restaurants and institutional food service operations (e.g., hospitals, universities, school districts, etc.). To enable landfill diversion on a large scale, more sustainable alternatives are needed, with the two most widely available commercial-scale options being composting and anaerobic digestion. However, these biochemical conversion processes have relatively long residence times, and their large physical size, high capital investment and O&M costs may ultimately limit widespread deployment. Thermochemical conversion under reduced oxygen conditions is another potential food waste management strategy worthy of serious consideration, especially for relatively low moisture content feedstocks that may be comingled with paper or plastic packaging waste. Our research has shown that biochar produced by thermochemical conversion of mixed food waste and other organic matter at temperatures of 500 to 1000^oC has favorable properties that may make it suitable as a soil amendment, adsorbent medium or in other applications such as sustainable building materials and printing inks. Moreover, we have shown that converting the solid fraction of the effluent from anaerobic digesters (“digestate”) to biochar can add economic value in an integrated biorefinery architecture that produces multiple co-products including electricity and thermal energy, and also offers the additional benefits of reduced greenhouse gas and wastewater emissions.