Torrefaction and Degradative Solvent Extraction As Means of Processing Rice Husk Waste

The high moisture level and ash content of biomass often hinder its further processing. In this study, torrefaction and degradative solvent extraction were employed to upgrade rice husk waste. Biomass torrefied at five different temperatures, in addition to dry raw biomass for comparison, was extracted in 1-methylnaphthalene at 300 degrees C for 1 h. Two solid fractions were obtained: extracted biomass (EB) and residue biomass (RB). The extraction yields of the EB and RB were 12-19.3% and 31.7-52% (db), respectively. The torrefaction temperature affected the extraction yields and slightly influenced product characteristics. The EB had almost no ash content as it was concentrated in the RB. However, both the EB and RB had higher heat values and carbon content as well as lower oxygen content than the raw biomass. Therefore, our findings suggest that EB could be utilized not only as fuel but also as functional materials.