Differentiating Bagasse and Straw as Feedstocks for Sugarcane Cellulosic Ethanol: Insights from Pilot-Scale Pretreatments

Abstract

Bagasse and straw are the two feedstocks used to produce cellulosic ethanol from sugarcane. Although this technology is advancing commercially, the differentiation between bagasse and straw remains elusive. This work investigates bagasse and straw supply, conditioning, and pretreatment in a pilot-scale steam-explosion continuous reactor (~ 10 kg/h feed) to illuminate the critical feedstock differences for process scale-up. Evaluating biomass across four sequential harvest seasons (2018–2021) shows that straw supplied in bales requires extra conditioning to reduce mineral matter and particle size before feeding into the reactor. Moreover, straw composition is more variable and consistently has lower contents of glucan (35.6–38.8%) and carbohydrate potential (glucose + xylose, 649–704 kg/dry tonne) compared to bagasse (40.8–42.9%; 735–760 kg/dry tonne). Biomass pretreatments without (190 °C, 5–15 min) and with sulfuric acid catalyst (149–170 °C; 5–15 min; 0.5–5.12%, m/m) show that straw differs from bagasse by presenting a higher acid neutralization capacity and about 5% of labile glucans. These results suggest that straw crushing and aqueous pre-extraction are promising strategies to reduce the dissimilarities with bagasse, thus facilitating the development of feedstock-agnostic biorefining.