Life cycle assessment of micro algae-based processes and products

Life cycle assessment (LCA) assesses the environmental impacts of products from cradle to grave. It is also possible to assess parts of the life cycle. Available peer-reviewed LCAs dealing with microalgae-based products and processes are reviewed. In processes that require extraction of dry algae, the combined harvesting, drying, and extraction steps are associated with relatively large environmental impacts. In addition, the cultivation stage has been identified as linked to relatively large environmental impacts. Proteins derived from cyanobacteria tend to have larger estimated life cycle environmental impacts than proteins derived from cultivated terrestrial plants such as maize and soybean. Microalgal biomass-based feed for carnivorous fish might have a lower life cycle environmental burden than conventional fish meal. Whether commercial microalgal fuels will have a climate benefit compared with fossil fuels appears to be uncertain. The energetic return on energy invested (EROI) of all microalgal fuels for which peer-reviewed LCAs are available does not meet the criterion of 5–8, which would allow for widespread application.