Production of algal biomass and its conversion to biofuels
are
important technological platforms within the larger umbrella of CO2 capture and utilization. This analysis incorporates a life-cycle
assessment (LCA) with respect to global warming potential and techno-economic
assessment (TEA) of algae biofuels, focusing on the sourcing and delivery
of CO2. This analysis evolves past work in this area to
include high-purity biogenic CO2, industrial fossil fuel
use, fossil power plants, and direct air capture, and uses a Sherwood
plot approach to estimate the CO2 capture energy penalty.
We also show that allocation or displacement facilitates a more intuitive
distinction between biogenic and fossil sources of carbon. Thus, the
LCA better reflects the influence of coproduct handling strategies
as compared to previous works. The TEA is also strongly influenced
by the CO2 concentration in the flue gas. Currently, when
CO2 is sourced from large-point sources, the price of biofuels
($4.5–6.5/GGE) may become comparable to fossil diesel. However,
as DAC systems become more economical, they may deliver competitive
CO2 sources for biofuels in 2050 with a total cost of <$7/GGE.
Based on the net emissions and costs, algae biofuels with CO2 sourced from biogenic sources are consistent with a decarbonized
economy as of now, with substantial potential for DAC with decreasing
costs.