Assessing environmental sustainability and value addition opportunities for by-products from aquaculture

Abstract

By-products and mortalities from aquaculture have often posed significant challenges to the industry because of their low value resulting in high costs and environmental impact from their disposal. However increasing interest is being expressed in their utilisation to add value to the aquaculture industry and provide synergies with industries which had previously been in competition with aquaculture. Current and prospective processing by-product and farm mortality utilisation strategies were reviewed along with regulations and standards which aim to control their use and protect against human and animal health hazards. The role of aquaculture and fishery by-products in the supply of fishmeal was investigated and it was found that both sectors had the potential to contribute to increasing global supply. There were significant quantities of processing by-products identified which could be directed to fishmeal manufacture but there were also significant amounts of fish production which were not being processed in some regions and could also add to supplies. Processing by-products from aquaculture species often exceed 50% of the production by mass and therefore their efficient utilisation is of significant importance to the overall performance of the value chain. Their utilisation strategies are diverse and in some circumstances offer the possibility to add significant value. Life Cycle Assessment (LCA) is increasingly being used to inform decision makers and consumers about the environmental performance of goods and services to make choices on best practices and informative decisions on purchasing choices. Current methodology in LCA was critiqued and developed to be used for identifying disproportionate impacts from by-product industries and comparative assessment of the eco-efficiency of value chains from Thai shrimp, Vietnamese Pangasius catfish and Scottish salmon aquaculture. New LCA methodology was developed assessing the eco-efficiency of co-products as a whole and in relation to a tonne of edible yield. Measuring the impact of the by-product industry in relation to their edible yield gave different results to measuring their eco-efficiency between the three study species. It was found that the Thai shrimp value chain was the most eco-efficient when by-products were directed to chitosan and hydrolysate manufacture, but production of the salmon was the least impacting between the species in terms of edible yield. Pangasius was the most environmentally impacting of the three species value chains using both methods. It was also found that the upstream impacts of fish and shrimp production, especially feed manufacture, contributed most to the environmental impact in most circumstances, using both economic and mass allocation. Although the methodology produced interesting results, there were some drawbacks and the data sets also had several gaps which led to some assumptions, which could have skewed the results and interpretation. The cause of mortality for five aquaculture species in five countries and their subsequent utilisation was investigated. It was found that extensive systems were more prone to mortality than intensive systems in many cases. There was a wide range of strategies for mortality utilisation. In countries where by-product industries existed, farmers were often able to sell some of their mortality losses but in other areas, disposal could create health and biosecurity hazards. In conclusion, it was found that both by-products and aquaculture mortalities could be utilised effectively and that the additional impact from their use was low in proportion to the rest of the value chain.