Abstract
In the present study, the protein-extracted grass residue (press cake) was processed through hydrothermal liquefaction under sub and supercritical temperatures (300, 350 and 400 °C) with and without using a potassium carbonate catalyst. The results revealed that bio-crude yield was influenced by both temperature and the catalyst. The catalyst was found to be effective at 350 °C (350 Cat) for enhancing the bio-crude yield, whereas supercritical state in both catalytic and non-catalytic conditions improved the quality of bio-crude with reasonable HHVs (33 to 36 MJ/kg). The thermal behaviour of bio-crude was analysed and higher volatile contents (more than 50% under the range of 350 °C) were found at supercritical conditions. The overall TOC values in the residual aqueous phase varied from 22 to 38 g/L. Higher carbon loss was noticed in the aqueous phase in supercritical conditions. Furthermore, GCMS analysis showed ketones, acids and ester, aromatics and hydrocarbon with negligible nitrogen-containing compounds in bio-crude. In conclusion, the catalytic conversion of grass residue under subcritical conditions (350 Cat) is favourable in terms of high bio-crude yield, however, supercritical conditions promote the deoxygenation of oxygen-containing compounds in biomass and thus improve HHVs of bio-crude.
Highlights
The utilization of non-renewable resources, especially fossil fuels, for energy production contributes to carbon emissions, resulting in climate change and global warming concerns
To decrease the concentration of greenhouse gas (GHG) emissions in the transportation sector, the utilization of advanced biofuels is considered as an attractive option
Under all temperatures with and without catalyst, the grass residue was successfully transformed into the bio-crude within the yield of 26 to 34%
Summary
The utilization of non-renewable resources, especially fossil fuels, for energy production contributes to carbon emissions, resulting in climate change and global warming concerns. To decrease the concentration of greenhouse gas (GHG) emissions in the transportation sector, the utilization of advanced biofuels is considered as an attractive option. In this case, the production of biofuels from lignocellulosic residues is well known and appealing due to the carbon-neutral cycle, along with waste management [2]. Different species of grass, such as switchgrass etc., have potential features as dedicated lignocellulosic feedstock that can play a vital role in the bioenergy sector [4,5,6]. Different species of grass residues are used for different applications related to foraging
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