Life Cycle Assessment of Soy Protein Isolate

Life cycle assessment (LCA) of food indicates that plant-based diets have lower impacts on the environment than those which include meat. However, such conclusions are based on a narrow representation of plant-based diets that excludes the growing number of meat substitutes available. These assessments therefore misrepresent the potential range of environmental impacts associated with plant-based diets, which depends in part on the foods people choose to fulfill their protein needs. Many realistic plant-based meat alternatives use soy protein isolate (SPI) to replicate the texture and nutritional profiles of a variety of meats. SPI uses soybean meal (soymeal) as a feedstock, which undergoes mechanical and chemical processing that in turn increases the environmental impact of the final product. The environmental impacts of SPI per kilogram are estimated here using LCA and expressed in terms of greenhouse gas emissions, freshwater eutrophication, land use, water depletion, fossil fuel use, and energy use. These results are compared to published values for soybeans, soymeal, tofu, chicken, pork and beef for reference. Publically available data, published literature and the ecoinvent database are used in SimaPro with the ReCiPe method to estimate environmental impacts associated with production of one kilogram of SPI. Results indicate that SPI has global warming potential higher than unprocessed chicken and pork, and similar to beef. Freshwater eutrophication associated with SPI is below impacts associated with chicken, pork and beef. Water depletion and fossil fuel depletion are higher in SPI than chicken, pork and beef. Energy use for SPI is lower than energy use for chicken, pork and beef. Land use associated with SPI is negative because of environmental credits from allocation to the byproduct of soymeal, soy oil and therefore represents a lower impact than chicken, pork, and beef. These findings demonstrate that this component of realistic fake meat may not be an environmentally preferable alternative to chicken, pork, or beef, depending on the impact categories considered.