Energetic valorisation of agricultural residues by solvent-based liquefaction

Abstract

The energy demand worldwide is ever-increasing with a growth of 2.3% registered in 2018. This means that there has also been an increasing demand for fuels. Biomass is an interesting alternative to fossil fuels as it contributes to a decrease of their adverse environmental effects. Nonetheless, biomass combustion may present several problems related to, for example, the initial moisture content and the increase of the emission of fine particles. This work describes the study undertaken regarding acid-catalysed liquefaction of different lignocellulosic biomasses as an alternative to process biomasses with high moisture contents and to decrease the emission of fine particles through the partial removal of the mineral matter of biomass. This process allows the production of a liquid biofuel which is more easily burned than the original biomass; moreover, it is also expected to reduce fly-ash forming species. Thus, olive stone/pits, olive bagasse, grape seeds and rice husk liquefaction was carried out at 160 °C using 2-Ethylhexanol as the solvent and a high biomass to solvent ratio of 1:1. In these conditions, a maximum conversion of 55% of the biomass into bio-oil was obtained for olive stone. On the other hand, 60–70% of the inorganic content of the biomasses was removed in the liquefaction stage. This result is an indication that, together with the production of a liquid biofuel, liquefaction can also be used as a pre-treatment to decrease the emission of fine particles associated to biomass combustion.