Assessing the environmental impacts and nutritional outcomes of Tilapia farming in Bangladesh

Abstract

There is an urgent need to transform global food systems into sustainable models which provide affordable, healthy, and micronutrient rich foods for all. This requires data-driven interventions and policies guided by rigorous food system performance assessments. Life Cycle Assessment (LCA) modelling is increasingly being used to evaluate the combined environmental and nutritional performance of food systems, known as nutritional Life Cycle Assessments (n-LCA). This thesis utilises novel n-LCA methodology to assess tilapia aquaculture and integrated agriculture-aquaculture systems in Bangladesh. The environmental and nutritional performance of fishponds, rice-fish co-culture, and poultry-fish co-culture was assessed by combining a nutrition metric, the Potential Nutrient Adequacy (PNA) metric, with LCA methods. Affordability assessments and food and nutrition security assessments were also performed to evaluate the economic and nutritional performance of the farming systems. Additionally, on-station experimental trials compared the environmental footprint and nutritional quality of four different tilapia strains cultured under intensive and semi-intensive feeding and harvesting regimes. A nutritional composition analysis was performed for tilapia taken from different farming systems across Bangladesh with results showing small tilapia, typically consumed whole, and large tilapia, from which only the flesh is eaten, have different nutrient contents due to the differences in consumption practices. Furthermore, diet, seasonality, and farm type significantly impact the level of nutrients in both small and large tilapias. Fishponds were found to have an overall better environmental performance compared to the rice-fish and poultry-fish farms. Results show feeds, fertilisers, energy, and chemical inputs have higher environmental impacts compared to other material inputs across all farm types. Result from the affordability assessment identified tilapia and two other fish species (Cirrhinus mrigala and Esomus danricus) as the most affordable sources of essential micronutrients and has shown these three fish species have a better environmental footprint compared to the other 17 fish species found in the farming systems and considered in this study. Results from the experimental trial, found the local strain had better productivity compared to the three genetically improved strains, and the intensively managed treatments performed better compared to the semi-intensive treatments in terms of nutritional quality and economic returns. When the nutrition metric was integrated into the LCA, results showed intensive treatments also performed better than semi-intensive treatments for several environmental impact categories. In conclusion, this thesis provides an important example of how nutrition can be combined with Life Cycle Assessments and offers insight into the impacts nutrition metrics can have on the overall results of performance assessments. Utilising the potential nutrient adequacy metric as a nutritional functional unit provides a more transparent approach to food system LCAs, although further development, testing, and validation of n-LCA methodology is needed to refine the process. This thesis also shows the nutritional quality of tilapia has been undervalued in the literature and that tilapia can provide sustainable, affordable nutrition to populations across Bangladesh.