Supercritical CO₂ extraction as an effective pretreatment step for wax extraction in a miscanthus biorefinery

The use of supercritical carbon dioxide (scCO₂) to extract valuable lipophilic compounds from miscanthus was investigated and subsequent enzymatic saccharification was carried out to determine the impact of scCO₂ extraction on downstream processing of miscanthus. Two miscanthus genotypes (Miscanthus x. giganteus and Miscanthus sinensis) were investigated and characterized. A diverse range of molecules were detected including long-chain hydrocarbons, fatty acids, n-policosanols, aldehydes, wax esters, sterols and steroid ketones. Quantification data indicates that there is a considerable difference among each species in the quantities of specific compounds. The waxes also exhibited significant differences in melting temperature, thus illustrating the opportunity for utilization in various applications. In addition to the isolation of valuable chemical compounds, the scCO₂ pretreatment also had a beneficial effect on the downstream processing of the biomass. The total sugars released after saccharification was found to increase by around 20% when coupled with scCO₂ extraction, as compared to untreated samples.