The primary energy and phosphorus consumption of soybean and seaweed-based aquafeed proteins - A Norwegian case study

In Norway, intensive production of farmed salmon is facing multiple challenges, and concerns about environmental impacts are strong [1]. Life Cycle Assessment (LCA) results show that feed is driving the environmental impacts of salmon aquaculture. During the last decade, aquafeed manufacturers started substituting large percentage of fishmeal with Soy Protein Concentrate (SPC). Today, 94% of the SPC used in Norway originate from Brazil [2]. The Brazilian soy industry activities are reported to result in deforestation, ecosystem degradation, resource depletion and greenhouse gas emissions in one of the world's most biodiverse regions. When looking for sustainable alternatives to Brazilian SPC, seaweed is one of the alternative feedstocks considered. LCA research has already documented the environmental impacts of soy protein products and Seaweed Protein Concentrate (SWPC). Yet, these studies were performed separately and in-depth, comparative environmental analysis of these two value chains is absent from the scientific literature. Thus, this study compares the environmental performances of two protein sources for aquafeed production: Brazilian SPC and Norwegian SWPC [3]. The efficiency and sustainability of these two production systems are assessed using a comparative material and substance flow methodology accounting for the transfers of primary energy and phosphorus. The primary energy and phosphorus demand of 1 t of SPC is compared to 2 t SWPC to assess commodities with similar protein contents. The primary energy consumption of the latter protein source (172,133 MJ) is found 11.68 times larger than for the soy-based concentrate (14,733 MJ). However, the seaweed protein energy requirement can be reduced to 34,010MJ if secondary heat from a local Norwegian waste incineration plant is used to dry the biomass after harvest. The seaweed system outperformed the soy system regarding mineral phosphorus consumption since 1 t of SPC requires 25.75 kg mineral phosphorus while 2 t of SWPC require only 0.008 kg. These results indicate that substituting soy protein with seaweed protein in aquafeed leads to an environmental tradeoff. The seaweed value chain produces proteins with near zero mineral phosphorus consumption by using naturally occurring marine phosphorus while the soy value-chain produces proteins for roughly 1/12th of the primary energy required by seaweed. Based on current technology, the seaweed value-chain require extensive innovation and economies of scale to become energy competitive. Hence, Norwegian studies investigate today the predictive environmental impacts of a fully developed SWPC value-chain and account for the background emissions and multi-functionality in each system. This work was conducted under the PROMAC project (www.promac.no) and financially supported by Research council of Norway.