Microbial lipids: Progress in life cycle assessment (LCA) and future outlook of heterotrophic algae and yeast-derived oils

There is an increasing interest in the replacement of traditional plant based glyceride oils with microbial oils for fuel, food, dietary supplements and other pharmaceuticals and chemicals. To understand the environmental implications of this technology a systems approach is required. To date the majority of Life Cycle Assessment (LCA) studies have addressed the use of photoautotrophic (light stimulated growth, atmospheric carbon fixing) microbes to produce biofuels. But, with an increasing number of biotechnology companies using heterotrophic (non-light stimulated growth, requiring an organic carbon feedstock) microbes for large-scale industrial food and consumer goods production processes, it is important that the environmental implications of heterotrophic technology for products outside of the energy sector are better understood. This review assesses the current life cycle literature available that relates to heterotrophic algae and yeast microbial oil production, evaluating where current gaps in knowledge and uncertainties lie. It also includes relevant LCA information from other production processes. Overall, the review finds significant gaps relating to both life cycle inventory and impact assessment information. Improved industrial data sets are needed, particularly for novel feedstocks, and cultivation and downstream processing towards non-fuel products. The implications of synthetic biology also need to be addressed. Impact assessment does not currently include a broad range of impact categories, focusing predominately on energy use and climate change. And to answer wider implications questions, further LCA studies are needed that take a more consequential approach. Addressing these areas is vital to ensure commercial viability, sustainability and public acceptance of the technology going forward.