Conclusions
HTL was identified to be a promising technology for the crude
bio-oil production from SCG. The preferable liquefaction conditions
were determined as: the reaction temperature of 275 C, retention
time of 10 min and water/feedstock mass ratio of 20:1. Under such
reaction conditions, the highest crude bio-oil yield of 47.3% mass
fraction was achieved with a higher heating value (HHV) of
31.0 MJ kg1, much higher than that of SCG which was only
20.2 MJ kg1. The energy recovery percentage was 72.6%. This work
is an attempt to utilize the waste stream from the coffee industries
for the bio-oil production via HTL. More research is needed and
recommended, including the liquefaction process conducted in
other solvents or co-solvents, and the investigation on the effects of
catalysts on the yield and composition of the resulting bio-oil.