To overcome the problem of rapid depletion of natural energy reserves and
consequent pollution caused by them, this work explored the possibility of
utilizing sewage sludge biomass to produce bio-oil using hydrothermal
liquefaction (HTL) pathway. In this study, effect of different reaction
parameters such as reaction temperature, residence time, and sludge-to-water
(ss-to-water) ratio on solid biomass conversion and bio-yield and its higher
heating value (HHV) were investigated. Although maximum conversion of (99.7
%) and highest bio-oil yield (22.01 wt%) was achieved at 330?C, however
optimum temperature was chosen as 300?C which produced conversion
efficiency and yield of bio-oil very close (98.07 % and 21.5 wt%
respectively) to what was obtained at 330?C as lower temperature is
beneficial for overall economy of the process. Similarly, a residence time
of 60 min and ss-to-water ratio of 1:6 was screened to be producing
optimized yield of bio-oil. HHV of different fractions bio-oil was much
improved (30.18 MJ kg-1 of acetone phase and 38.04 MJ kg-1of DCM phase) as
compared to that of raw feedstock (12.74 MJ kg-1). Carbon balance performed
on the products indicated that maximum amount of carbon went to bio-oil
phase (53.4 wt%). However, a significant portion of carbon was lost (33.9
wt%) due to the limitation of experiments at lab scale which involves
evaporation and drying to reach final products. FTIR spectral analysis of
different bio-oil phases showed that it was mainly made up of alcohols,
alkane, ketones, aldehydes and carboxylic acids.