Microalgae is a promising biofuel feedstock due to its ability to
grow on non-arable land, does not compete with food, and high
yield. LCA currently is being used to assess the large-scale feasibility
and environmental impact of alternative processing technologies
being explored for processing microalgae as a feedstock into
biofuels. This study integrated experimental and literature data
for systems engineering model validation to perform an environmental
impact and energetic assessment of two different thermochemical
conversion technologies, HTL and pyrolysis. Both
conversion pathways result in unfavorable NER results with
advances in HTL processing expected to improve energetics. Pyrolysis
has proven to be an effective way of converting biomass to a
biofuel precursor, however on a systems processing level there are
challenges associated with microalgae as a feedstock. The biggest
challenge comes from drying the microalgae which represents an
energy intensive process. The pyrolysis sub-process with microalgae
has the potential to be a self-sustaining process, with the ability
to recovery nearly two thirds of the total process energy
through heat recovery and the burning of byproducts. Excess
energy in the pyrolysis process can be used in other processing
steps such as drying. The extra energy is limiting to approximately
20% of the energy required in the drying process with the
remaining energy derived from natural gas. Results from this study
show the pyrolysis pathway is not energetically or environmentally
favorable. This is primarily due to microalgae drying dominating
the energetics of the process.