Emergent chemical behavior in mixed food and lignocellulosic green waste hydrothermal liquefaction

Abstract

Hydrothermal liquefaction (HTL) is a promising strategy for conversion of energy-dense waste streams to fuels. Mixed-feed HTL aggregates multiple feed streams to achieve greater scales that capitalize on local resources, hence lowering costs. The potential for new pathways and products upon feedstock blending becomes a compounding level of complexity when unlocking emergent chemistries. Food and green waste streams were evaluated under HTL conditions (300 °C, 1 hr) to understand the effect of feed molecular composition on product distributions and mechanisms. Thousands of emergent chemical compounds were detected via FT-ICR MS, ultimately leading to the emergence of two dominant outcomes. First, the presence of small amounts of food waste into green waste results in substantial decarboxylation and subsequent polymerization to biocrude then chars. Second, in the other limit, small amounts of green waste promote capping of oxygenates into the biodiesel range, such as with the emergence of fatty acid methyl esters.