A thorough literature review encouraged us to explore the
feasibility of converting the spent coffee grounds (SCG) to bio-oil
via HTL. SCG has higher contents of lipid (z15%) and protein
(z17.4%), while a lower content of lignin (z23.9%), compared to
the lignocellulose biomass [11,12,53]. It might be a promising
feedstock for the bio-oil production using the HTL technology. More
attractively, the size of SCG is in the range of 200e300 mm [19],
which makes it suitable for being directly fed to the HTL reactor
without a prior energy-intensive grinding process.