Comparison with the relevant studies
A variety of low value biomass have been investigated as feedstock
for the crude bio-oil production via HTL, including agricultural
and forest residues, food-processing waste, animal manure
and municipal solid waste (MSW), etc. Our present study was a first
attempt to produce the crude bio-oil from SCG, therefore, it is
necessary to compare the results obtained with other studies in this
field to evaluate the feasibility and the promise of SCG liquefaction.
It is important to point out that this comparison is a generally
qualitative comparison, as each feedstock was liquefied under
different conditions as reported in the literature.We made our best
effort to select the cases in which liquefaction conditions were close
to our experimental conditions (water as a medium and in nitrogen
atmosphere without any catalysts application).
Table 3 provides the properties of bio-oils derived from the HTL
of SCG and other representative biomass. In general, the crude biooil
derived from SCG liquefaction has a much higher yield (47.28%)
and a slightly lower HHV(31.0 MJ kg1), compared to the crude biooils
derived from lignocellulose-based biomass such as Jack pine
wood sawdust, corn stalk, tea waste, and pulp/paper sludge.
However, the reaction condition employed in the HTL of SCG is
milder or more favorable than the HTL of lignocellulose biomass,
for example, a lower temperature and a shorter retention time. In
terms of the composition, the crude bio-oil from SCG is composed
of long-chain carboxylic acids. No phenolic compounds were
detected, which is very different from the crude bio-oils generated
from other lignocellulose feedstock. This may be attributed to a low
lignin content in the SCG and various liquefaction conditions.