Hydrothermal liquefaction of agricultural and forest biomass residue: comparative study

Biomass is a promising feedstock for the production of valuable oxygenated hydrocarbons due to presence of wide range of functionalities. Hydrothermal liquefaction is an attractive approach for the conversion of lignocellulosic biomass as it does not require any drying. The objective of this study is to carry out hydrothermal liquefaction (280 °C for 15 min) of forest (pine wood, deodar) and agricultural (wheat straw, sugarcane bagasse) biomass under non-catalytic and catalytic (KOH, K₂CO₃) conditions. The analysis of solid residue and bio-oils was carried out to understand the differences in composition with respect to feedstock. Agricultural biomass showed higher conversion under thermal and catalytic conditions compared to forest biomass. K₂CO₃ showed higher catalytic activity in terms of both bio-oil yield as well as conversion for agricultural (wheat straw and sugarcane bagasse) biomass compared to forest (pine wood and deodar) biomass. Sugarcane bagasse showed the highest conversion (95 %) among the four samples investigated. The compositions of bio-oils from forest biomass residue contained both phenolic compounds and furans. FTIR and Powder XRD analysis of feedstock as well as solid residue showed that the peaks due to cellulose, hemicellulose and lignin became weak in solid residue samples.