Similarities in the results from the sensitivity analysis for the
two thermochemical processes modeled exist as expected. The
bio-oil yield represents the functional unit and changes in the yield
from the conversion processes will have the largest impact on the
system on the metrics of NER. Other inputs shown to be sensitive
in the NER sensitivity include reactor energy and recovery of nutrients.
Nutrient recycle has been identified as a critical step in the
large-scale feasibility of microalgae based biofuel systems
[30,77]. For the pyrolysis pathway drying energy and recovery
energy are also sensitive as they have a significant impact on the
overall process energetics. Sensitivity in GHG emissions for the
respective conversion pathways are shown in Fig. 7B and D. Parameters
found to be most sensitive in both conversion methods
include emissions associated with conversion and emissions associated
with growth in the raceway which are primarily a result of
nutrient requirements. In the pyrolysis process drying of microalgae
and burning of process byproducts were also found to be
sensitive.