Green biorefinery of giant miscanthus for growing microalgae and biofuel production

Abstract

In this study, an innovative green biorefinery system was successfully developed to process the green biomass into multiple biofuels and bioproducts. In particular, fresh giant miscanthus was separated into a solid stream (press cake) and a liquid stream (press juice) using a screw press. The juice was used to cultivate microalga Chlorella vulgaris, which was further thermochemically converted via thermogravimetry analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis, resulting in an approximately 80% conversion. In addition, the solid cake of miscanthus was pretreated with dilute sulfuric acid and used as the feedstock for bioethanol production. The results showed that the miscanthus juice could be a highly nutritious source for microalgae that are a promising feedstock for biofuels. The highest cell density was observed in the 15% juice medium. Sugars released from the miscanthus cake were efficiently fermented to ethanol using Saccharomyces cerevisiae through a simultaneous saccharification and fermentation (SSF) process, with 88.4% of the theoretical yield.