Semi-continuous hydrothermal process for conversion oat husks to fuel and precursors

The hydrothermal process uses water as a solvent and high thermodynamic condition for converting lignocellulosic biomass, being an environmentally friendly and promising alternative. Subcritical water conditions were exploited for hydrolysis carbohydrates, including cellulose and hemicellulose, present in oat hulls, in order to produce biofuels and precursors as platform chemicals and fermentable sugars. A synergistic conversion of lignocellulosic biomass at the evaluated temperatures (300 and 330 °C) and 20 MPa, makes the process versatile for producing different products. Under these drastic temperature and pressure conditions, it was a challenge to operate in semi-continuous mode due to difficult temperature control and blockages in the process lines. At 300 °C, the highest yields of fermentable sugars (4.98 g/100 g oat hulls) and platform chemicals (5.48 g/100 g oat hulls) were obtained for both solvent-to-feed ratios (S/F 3.7 and S/F 60). The greatest bio-oil yield (43.11 g/100 g oat hulls) was achieved at 330 °C under the same solvent/feed conditions.