Renewable Fuel Production Via Electrocatalytic Co-Processing of Biomass-Derived Aqueous Waste and Bio-Oils at Normal Temperature and Pressure

Abstract

Electrocatalytic conversion is emerging as a potentially attractive low-cost approach to distributedly process biomass-derived streams. Conventional upgrading processes require moderate temperatures between 433 and 678 K, pressures of 14,000 kPa, and external sources of dihydrogen; however, the same upgrading reaction can be performed using electrochemical reactors and much lower temperatures and pressures (293 K and 101 kPa) and with no supplied hydrogen (H2).1-4 In this work, we evaluate the electrocatalytic conversion of aqueous waste and bio-oils generated during biomass liquefaction via hydrothermal liquefaction (HTL) and pyrolysis at room temperature and atmospheric pressure. The main biomass-derived compounds (carboxylic acids, alcohols, ketones, etc.) can be upgraded via electrocatalytic oxidation (ECO) into olefins, paraffins, and alcohols following the (non-)Kolbe electrolysis.2, 5 Alternatively, the same compounds could not be upgraded via electrocatalytic hydrogenation (ECH) over a variety of noble and base metals, instead H2 evolution and aldehyde ECH were the preferred reaction.1, 3 Preliminary techno-economic analysis shows that the capital cost associated with the integrated electrocatalytic process for the aqueous waste treatment and H2 generation can be up to 80% lower than the combined cost for traditional thermal (e.g., gasification) and biological (e.g., anaerobic digestion) wastewater treatment, and H2 generation (via natural gas steam reforming), and can lower the minimum fuel selling price (MFSP) by up to $0.84/GGE (Figure 1). Additionally, the operation (electricity) cost can be offset by the sale of the excess H2 generated (valued at >$2/kgH2) specially when operating at low full cell potentials (<4.5 V) and using low electricity cost (<4¢/kwh).2 Figure 1