Animal Feed from Microalgae Grown on Biogas Digestate as Sustainable Alternative to Imported Soybean Meal

This work investigates microalgae’s potential to reduce North-Western Europe environmental burden from excess nitrogen polluting groundwater and provide an environmental replacement for current animal feed. Algae uptake nutrients from nutrient-rich digestate from biogas plants and turn them into high-value feedstock, which can substitute soybean meal imported from overseas and avoid deforestation of rainforests. Life cycle assessments were conducted based on novel and original data from engineers in academia and industry, acquired through pilot-scale research facilities in the UK, France, and Belgium. The findings of this study highlight the environmental impacts of three different technologies with varying scales of production. Mixotrophic algal feed production shows higher productivities and fewer energy demands than the phototrophic systems. Still, the process is less favourable due to higher impacts on human health and ecosystems than imported soybean meal, whereas the impact on resources is more negligible. Sensitive analysis indicates that further technological development, increased productivities, and renewable energy use can improve the environmental competitiveness of algal feedstock. Since this process is a promising solution for making feedstock out of excess nutrients and having an alternative source for imported soybean meal with a comparable, efforts to realize these improvements and successfully upscaling algal feedstock production in combination with biogas plants are justified and can improve the environmental footprint of algal biomass production.