Biomass based biofuel production systems benefit from a carbon
credit associated with the uptake of carbon dioxide in the
growth phase. The GHG emissions for a WTP systems boundary
for the HTL pathway results in net negative CO2-eq emissions of
11.4 g CO2-eq MJ1. The aqueous phase from the HTL unit contains
ammonium and phosphite, which represent a co-product credit,
and is assumed to be recycled and supplement the nutrient
requirements for microalgae growth. In terms of GWP, a benefit
of bio-oil recovery through HTL results from the processing of a
wet microalgae slurry, eliminating the energy and GHG emissions
associated with drying. In addition, HTL processing produces a
small quantity of combustible gases which are burned to improve
the energetics of the system. Compared to conventional diesel, the
HTL pathway for the production of renewable diesel results in a
32.5% reduction in GHG emissions based on a WTW system