Abstract
Despite the contribution of prawn (Macrobrachium rosenbergii) production has been considered to grip excellent promise for creating jobs, earning overseas money and supplying protein; a number of issues including environmental aspects of freshwater prawn farming in Bangladesh are important for sustainable trade, as consumers of importing countries are demanding environmentally friendly product. Life cycle assessment (LCA) has been promoted as a good tool for evaluating seafood products. This study was aimed to evaluate overall resource use and environmental impact caused by three prawn farming systems (Pond, Dogi and Gher), and to identify hotspots and improvement options. The inventory covered the entire chain from prawn brood collection to prawn harvesting at farm, mentioned as "cradle to farm gate". Three functional units based on area (one hectare), weight (one tonne) and calorie content (one gigajoule) were adopted. Allocation by economic value was applied to allocate environmental burdens in case of multiple outputs. To assess the environmental impact, the last update of the CML impact assessment method was used. Selected impact categories included global warming, acidification and eutrophication. Life cycle inventory (LCI) and life cycle impact assessment (LCIA) results were calculated using CMLCA software (Version 5.2). Prawn feed (commercial pellet feed and on farm feed ingredients) was identified as the major contributor for the environmental impacts for all farming systems. Among different feeds, commercial pellet feed had the largest contributions to global warming (36.5%), acidification (64%) and eutrophication (47%) in pond system. Wheat based products altogether contributed most to global warming (46%), acidification (62%) and eutrophication (25%) in Dogi system. In Gher, commercial pellet feed had the largest contributions to global warming (40%) and acidification (46%), and pulse products together contributed most to eutrophication (38%). The sensitivity analysis by mass allocation for co-product allocation decisions revealed the overall lifecycle impacts resulting from the two allocation methods (mass and economic) varied notably, but often came to the similar conclusions. This LCA study highlighted the advantages of using LCA to identify the hot spots, rather than comparing different aquaculture systems, especially when there are diversification in integration and management practices, and differences in outputs. Rice-prawn integrated farming was identified as an environmentally friendly technology. Improving the efficiency of commercial feed formulation, best management of capture fisheries for dried fish, expansion of soybean farming in less competitive agricultural farming zones, use of potato starch instead of wheat as binder, increased use of the de-oiled rice bran instead of using rice bran, proper management of snail from nature and initiative of snail culture in pond, practices of crop rotation and production of high yield varieties for pulses, and increasing the current level of prawn production through best management practices were the major recommendations to lower the environmental burdens of prawn farming in Bangladesh.