Drop-in fuel production from food waste: system level optimization and analysis

One third of food produced for human consumption is lost or wasted globally, with most of this waste currently being landfilled or treated by anaerobic digestion. Landfilling occupies land without resulting in any valorization, while anaerobic digestion is not effective in recovering energy or any valuable products. This paper proposes a synergistic approach for the conversion of food waste to high-quality, renewable jet fuel. Hydrothermal liquefaction is employed to transform high-protein wet waste to biocrude oil, which can then be upgraded into transportation fuel. The wastewater generated by hydrothermal liquefaction is valorized to hydrogen using a microbial electrochemical (MEC) technology. We perform system-level optimization to Identify promising system configurations and assess their economic, environmental, and energetic performance, as well as identify the major cost drivers. Thereby, the focus lies on system-wide performance and insights rather than the details of individual system components, which are based on experimental data. Although the system exhibits enhanced carbon efficiency in comparison to anaerobic digestion, it is currently expensive when compared to other treatment processes. Nevertheless, potential improvements in the hydrothermal liquefaction and microbial electrolysis technologies could improve system economics. Particularly, a reduction in capital costs and ability to handle higher COD concentrations at the MEC inlet could render the system economically more viable. Moreover, we find that availability of greener electricity and the implementation of policies such as a carbon tax can render the proposed system competitive with currently used technologies.