Powering lignocellulose biorefineries with solar energy – A critical review with furfural as a case study

Abstract

In the context of a circular carbon economy, biorefineries are set to replace traditional petrochemical installations. While a standard biorefinery model involves the use of decarbonized electricity and reactive gases (such as H2 from electrocatalytic water splitting) to process and upgrade biomass resources, more integrated approaches can be envisioned. In particular, the direct use of solar energy and water as a source of protons in solar-powered electrolysers, photoelectrocatalytic and photocatalytic devices appears attractive. However, the range of chemical transformations accessible through thermocatalytic, electrocatalytic or photocatalytic processes varies greatly, and so do the corresponding operating conditions. Therefore, it is still unclear whether integrating integrated solar strategies to biorefineries would be energetically and economically efficient. In this critical review, we provide elements to address this outstanding question for lignocellulose biorefineries. First, we provide a comparative overview of the current state-of-the-art of catalytic processes for lignocellulose valorization by thermochemical, electrochemical and photoelectrochemical/photochemical approaches, along with their required energy input and operating conditions. Then, we propose a case study on lignocellulose-derived furfural hydrogenation, in which we evaluate the opportunity of replacing established thermocatalytic processes with solar-powered electrochemical processes. We show that there exist a range of conditions in which it is more beneficial to transform furfural electrochemically, and that expanding these considerations to other biomass valorization processes would be useful. Finally, we describe how including integrated solar-powered chemical transformation into biorefinery plants unlocks novel strategies and synergies for future biorefinery designs. Overall, we conclude that there is an interest in supplying solar energy and electrons directly to the catalytic transformations, provided that dedicated and specific catalysts and reactor designs are developed for this purpose.