PNNL

Abstract

The global transition to net-zero necessitates a more sustainable management of wet waste – which is currently being landfilled or used for anaerobic digestion. Hydrothermal liquefaction has emerged as a promising technology which converts wet waste to biocrude and biofuels. Nevertheless, the recalcitrant wastewater associated with this process has hindered its realization at industrial scale. In this work, we designed and constructed pilot microbial electrolysis cells with a total volume > 250 L and operated it onsite alongside pilot hydrothermal liquefaction reactor for treatment of hydrothermal liquefaction wastewater for over 3 weeks. The long-term (3 months) operation conducted on a single reactor in lab demonstrated a successful inhibition of methanogens and acetogens without dosing specific inhibitor, resulting in high-purity H2 and high hydrogen recovery. The optimal COD-to-H2 yield observed under onsite conditions were able to support a self-sufficient, closed-loop upgrading to jet fuel. Moreover, analysis on biofilm revealed a high enrichment of Geobacter spp. and the spatial heterogeneity was most prominent on vertical scale.