Supercritical extraction as an effective first-step in a maize stover biorefinery

Abstract

Supercritical carbon dioxide (scCO₂) has been investigated for the generation of valuable waxy compounds and as an added-value technology in a holistic maize stover biorefinery. ScCO₂ extraction and fractionation was carried out prior to hydrolysis and fermentation of maize stover. Fractionation of the crude extracts by scCO₂ resulted in wax extracts having different compositions and melting temperatures, enabling their utilisation in different applications. One such fraction demonstrated significant potential as a renewable defoaming agent in washing machine detergent formulations. Furthermore, scCO₂ extraction has been shown to have a positive effect on the downstream processing of the maize stover. Fermentation of the scCO₂ extracted maize stover hydrolysates exhibited a higher glucose consumption and greater potential growth for surfactant (in comparison with non-scCO₂ treated stover) and ethanol production (a 40% increase in overall ethanol production after scCO₂ pre-treatment). This work represents an important development in the extraction of high value components from low value wastes and demonstrates the benefits of using scCO₂ extraction as a first-step in biomass processing, including enhancing downstream processing of the biomass for the production of 2^nd generation biofuels as part of an integrated holistic biorefinery.