Life Cycle Assessment of Single Cell Protein production – A review of current technologies and emerging challenges

Population growth trend will have a significant impact on the availability of food resources, leading to a surge in the development of various protein concentrates, including Single Cell Protein (SCP), which is derived from the biomass of unicellular organisms. The objective of this review is to analyze the application of Life Cycle Assessment (LCA) on SCP production, assessing the influence of the technologies on environmental outcomes and the challenges linked to LCA methodological choices. The articles included in the review were classified according to their LCA goal, distinguishing between those focused on the production of SCP for consumption, for feed valorization, for wastewater treatment and for conventional foods substitution in meals. Generally, most systems comprised three stages: feedstock production and pre-treatment, fermentation, and post-treatment, and in some cases, integration of SCP into the final product. The analysis revealed that the type of substrate has a great influence on the environmental profile of the product, as well as its pre-treatment. Electricity was also identified as the main hotspot in virtually all systems, being the most studied parameter in sensitivity analyses. Regarding the definition of LCA parameters, a lack of consensus on the description of system boundaries in the use of organic waste as substrate for SCP production is notable, leading to confusion about the actual associated impacts. Likewise, the study of the environmental performance of SCP based on its amino acid content and nutritional quality is one of the main challenges that would contribute to better evaluating its environmental behavior compared to other types of protein of vegetal and animal origin.