Life cycle assessment of fish and prawn production: Comparison of monoculture and polyculture freshwater systems in Brazil

Abstract

This study applied life cycle assessment (LCA) to evaluate and compare environmental impacts of monoculture and polyculture systems in freshwater ponds. Two omnivorous native Brazilian species were used: the fish tambaqui (Colossoma macropomum) and the Amazon River prawn (Macrobrachium amazonicum). Four semi-intensive aquaculture systems (at an experimental level) were established and studied: monoculture of C. macropomum (MM), monoculture of M. amazonicum (MA), polyculture in which both species were free in the pond (PF), and polyculture in which C. macropomum was reared in a hapa cage and M. amazonicum was free in the pond (PH). The MM, PF and PH systems were fed fish feed, while MA was fed shrimp feed. Water was not renewed, but added only to replace losses from evaporation and seepage. Seven impact categories were analyzed: climate change, eutrophication, cumulative energy demand, land occupation, acidification, net primary production use and water dependence. Potential impacts of 1 kg of animal biomass produced by the systems were calculated, as was uncertainty in predictions based on uncertainty in data for the systems. Environmental impacts of each species in the polyculture systems were estimated using system expansion and different allocation approach: mass, energy and economic. PF and MM had the lowest impacts in all impact categories, while MA had the highest. When economic allocation was used, PF had lower impacts than MM per kg of C. macropomum. The rearing stage itself was the main contributor to eutrophication, land occupation and water dependence. However, feed was the main contributor to acidification and net primary production use in all systems. Only for PH was feed not the most significant contributor to climate change. Productivity and feed conversation ratio were key factors that defined the most efficient system from an environmental viewpoint. Our study demonstrated the advantage of rearing M. amazonicum in a polyculture instead of a monoculture, while no difference was found for C. macropomum. Changing the allocation approach revealed that aquaculture of M. amazonicum has lower impacts when the species is reared in polyculture systems. Moreover, aquaculture of native species remains in the early stages, and further development of its production chain may decrease its environmental impacts.

Overview of strategies that contribute to the environmental sustainability of pond aquaculture: rearing systems, residue treatment, and environmental assessment tools

“…LCA is a methodology developed by the International Organization for Standardization ISO (2006a,b) to estimate the environmental impacts and identify processes that are less efficient from the environmental point of view. It was developed by the industrial sector, and since the year 2000, several LCA studies related to aquaculture species and rearing systems have been published (Pelletier & Tyedmers 2010;Cao et al 2011;Jerbi et al 2012;Huysveld et al 2013;Aubin et al 2015;Medeiros et al 2017). This methodology is divided into four major steps: goal and scope, inventory, impact assessment and interpretation of results.…”

“…; Medeiros et al . ). This methodology is divided into four major steps: goal and scope, inventory, impact assessment and interpretation of results.…”

Life cycle assessments of aquaculture systems: a critical review of reported findings with recommendations for policy and system development

“…; Medeiros et al . ). To maximize the benefits, the set of species grown together needs to be chosen with different feeding habits so that they can benefit from each other's by‐products and reuse nutrients across taxa (Auburn University ).…”

LCA of aquaculture systems: methodological issues and potential improvements

“…As evidenced in the sensitivity analyses of numerous LCA studies included in the current review (e.g. Winther et al 2009;Kluts et al 2012;Wilfart et al 2013;Aubin et al 2015;Jonell and Henriksson 2015;McGrath et al 2015;Nhu et al 2016;Medeiros et al 2017), the choice of method to solve process multi-functionality is of great importance for the LCA results.…”