Review of Life-Cycle and Techno-Economic Analyses for Algae Systems: Bottlenecks to Sustainability

It is increasingly suggested that bioremediation of atmospheric carbon dioxide (CO₂) can be achieved by fixing CO₂ as algal biomass. This topic has been the subject of numerous life-cycle analyses (LCAs) in recent years, which have attempted to assess the environmental impacts of such processes, with mixed conclusions. Authors of techno-economic analyses (TEAs) have endeavored to determine the practical feasibility of algae production systems, but it is difficult to draw conclusions from their results due to uncertainty surrounding the wide variety of process designs proposed for this immature technology. To date, no comprehensive review of publicly-available LCAs and TEAs has been published.

Herein we have assembled a critical review of studies that have been published, and provide some illustrative benchmarking calculations based on fundamental relationships. It is clear that analysis of the detailed process designs and operations is necessary to quantify the potential sustainability of a system: in short, sustainable production of algal biomass is not an a priori result of all process scenarios. Good LCA studies identify major technical and economic lever points, but this step is often overlooked. It appears likely that co-production of high-value products (in addition to biofuels) is the most economically efficient way to lower carbon footprints of industrial CO₂ emitters.