Accounting for inventory data and methodological choice uncertainty in a comparative life cycle assessment: the case of integrated multi-trophic aquaculture in an offshore Mediterranean enterprise

Abstract

Purpose Integrated multi-trophic aquaculture (IMTA), growing different species in the same space, is a technology that may help manage the environmental impacts of coastal aquaculture. Nutrient discharges to seawater from monoculture aquaculture are conceptually minimized in IMTA, while expanding the farm economic base. In this study, we investigate the environmental trade-offs for a small-to-medium enterprise (SME) considering a shift from monoculture towards IMTA production of marine fish. Methods A comparative life cycle assessment (LCA), including uncertainty analysis, was implemented for an aquaculture SME in Italy. Quantification and simultaneous propagation of uncertainty of inventory data and uncertainty due to the choice of allocation method were combined with dependent sampling to account for relative uncertainties and statistical testing and interpretation to understand the uncertainty analysis results. Monte Carlo simulations were used as a propagation method. The environmental impacts per kilo of fish produced in monoculture and in IMTA were compared. Twelve impact categories were considered. The comparison is first made excluding uncertainty (deterministic LCA) and then accounting for uncertainties. Results and discussion Deterministic LCA results evidence marginal differences between the impacts of IMTA and monoculture fish production. IMTA performs better on all impacts studied. However, statistical testing and interpretation of the uncertainty analysis results showed that only mean impacts for climate change are significantly different for both productive systems, favoring IMTA. For the case study, technical variables such as scales of production of the species from different trophic levels, their integration (space and time), and the choice of species determine the trade-offs. Also, LCA methodological choices such as that for an allocation method and the treatment of relative uncertainties were determinant in the comparison of environmental trade-offs. Conclusions The case study showed that environmental trade-offs between monoculture and IMTA fish production depend on technical variables and methodological choices. The combination of statistical methods to quantify, propagate, and interpret uncertainty was successfully tested. This approach supports more robust environmental trade-off assessments between alternatives in LCAs with uncertainty analysis by adding information on the significance of results. It was difficult to establish whether IMTA does bring benefits given

A critical perspective on uncertainty appraisal and sensitivity analysis in life cycle assessment

“…One immediate implication of this finding is that only assessments where the differences among options are pronounced can be considered meaningful. However, few contributions acknowledge that overlapping output uncertainty ranges may challenge ranking reliability in a comparative analysis (Mendoza Beltran et al, 2018;Muñoz et al, 2014).…”

Integrated multi-trophic aquaculture of red drum (Sciaenops ocellatus) and sea cucumber (Holothuria scabra): Assessing bioremediation and life-cycle impacts

“…It is important to include uncertainty analysis in comparative LCAs, since deterministic results that do not include significance information can lead to oversimplified conclusions (Mendoza Beltran et al, 2018), especially in ex-ante analysis. Uncertainties due to unrepresentativeness (i.e.…”

“…In the IMTA system, the additional 3 t of sea cucumbers (and 109 kg of edible protein) represented a minor increase in annual farm production; therefore, finfish production still drove the impacts. Mendoza Beltran et al (2018) reported and discussed this issue when comparing impacts of a finfish monoculture (240 t) to those of the same farm in an IMTA system with oysters (244 t of aquatic products). They estimated similar differences between the two systems (0.4-1.8% depending on the impact category)…”

“…LCA has been used mostly to identify problematic stages or components of systems and to compare alternatives such as intensive vs. extensive systems, monoculture vs. polyculture and open water vs. closed recirculating systems. To date, only a few LCA studies have examined the potential of IMTA systems to mitigate aquaculture impacts (Mendoza Beltran et al, 2018;Mendoza Beltrán and Guinée, 2014). In this context, the present study examined environmental benefits and trade-offs for finfish monoculture of shifting to an open-water IMTA system co-culturing suspended sea cucumber culture beneath finfish cages, by assessing the latter's mitigation potential at local and global scales.…”

Strategic considerations for establishing a large-scale seaweed industry based on fish feed application: a Norwegian case study

“…Another important environmental benefit from cultivating seaweed is the sequestration of nutrients and CO 2 from the water (Seghetta et al 2017). The sequestration of nutrients is even higher when cultivation happens in connection to fish farms as in an IMTA configuration (Beltran et al 2017), where some of the excess nutrients from the fish farms are incorporated by the algae. When it comes to the processing of the seaweed, the literature focuses on drying technology whereas the investigation of SPP production in this study will focus on freezing technology.…”