Introduction
Low trophic aquaculture, such as bivalve species (i.e., mussels) , are candidate species for the minimization of environmental impact of worldwide growing aquaculture, while providing with ecosystem goods and services. Nowadays, mussels are cultured suspended mainly in raft and longline systems, using ropes made of non-biodegradable fossil-based plastics , which use could result in augmenting marine litter and microplastics entering the oceans . The EU BIOGEARS project validated bio-based and compostable ropes ( hereinafter referred to as “biogears ”) as more sustainable solutions than existing commercial counterparts for suspended mussel production in offshore longline systems. Integration of biogears into low trophic aquaculture infrastructures holds promise for enhancing the efficacy of these practices as nature-based solutions. However , defining and advancing the pathway for implementing such aquaculture gears remains a challenge. The aim of this study is to assess the route for the implementation of bio-based ropes in low trophic aquaculture alongside further appraising the effectiveness of such aquaculture practices as nature-based solutions.
Material and methods
Two biogears ropes prototypes (B1 and B2) were developed based on compounds of commercially available biopolymers and manufactured with industrial processes to be fit-for-purpose , with technical and functional properties similar to commercial mussel rope counterparts. T he sustainability assessment of biogears was conducted by comparison with fossil-based counterparts regarding to technical characteristics ( a one-year mussel longline production) , environmental performance (compostability and Life Cycle Analysis) and economic outcomes (cost and benefit analysis along the value chain and ecoefficiency . The compostability tests were conducted in laboratory (58±2 ºC) simulating industrial composting conditions (UNE EN ISO 14855 /UNE-EN 13432). The co-efficiency indicator was calculated according to ISO 14045:2012 and LCA according to ISO 14040/14044 , respectively. In the light of promising results of biogears, the next step is to implement them in the sector and mussel productions as nature-based solutions (NbS). I n Biogears project the potential implementation of biogears in the European aquaculture sector was assessed considering , 1) the current context (considering technical, environmental, policy, etc., aspects of biogears ), 2) the potential circular value chain, 3) a consultation to stakeholders (by online surveys and personal interviews), 4) a BlueLab concept (considering the principal stakeholders involved in the value chain), and 5) end-of-life (EoL ) biogears best practices . Aligning this implementation context with NbS is a challenge that will be overcome in a subsequent project to BIOGEARS , TRANSEATION (Proposal ID 101135343): Advancing Ecosystem-Based Management through Hybrid Blue-Grey Infrastructures in Marine and Coastal Areas). Within this project, efforts are underway to enhance the mechanical properties of biogears prototypes to improve their durability in mussel aquaculture settings. Furthermore, the assess ment of the effectiveness of low trophic aquaculture productions ( mussel longline and raft cultures) as NbS including the implementation of biogears will be conducted .
Biobased ropes promoted similar mussel growth but higher mussel productions per rope linear meter ( 85% in B2 and 23% in B1) with respect to the fossil-based rope counterpart (4.29 kg/m). Overall, mussel quality was not compromised by using biobased ropes (similar Condition Index, meat yield, proximal composition and fatty acid profiles as in mussel grown-out in fossil-based ropes). Mechanical properties (l oad at b reak and elongation) of biogears did not compromise rope functionality in one-year mussel production while holding a higher mussel weight. Compostability tests concluded that industrial composting of biogears is technically feasible and validated composting as EoL option for biobased ropes. L ife Cicle Analysis showed that, considering rope aquaculture production (impact/kg mussels produced per rope linear meter), B2 was the best environmental performing rope , as reducing by 20% the environmental footprint ( 34% reduction of the carbon footprint and 63% reduction of the use of fossil resources) along the whole value chain compared to conventional fossil-based ropes. The economic evaluation revealed that the enhanced productivity of mussels in B2 ropes could counterbalance the present cost disparity in biogears production, attributed to the relatively higher market price of biobased materials. Consequently, the adoption of biogears would render mussel production more economically viable compared to employing commercial fossil-based ropes. Additionally, the eco-efficiency analysis emphasized the importance of promoting the production and utilization of B2 prototype ropes due to their superior eco-efficiency indicators, considering both the environmental impact and economic value per kilogram of harvested mussel. From these results, it can be concluded that biogears , and specifically biobased B2 ropes, can be technical, economic and environmentally sustainable alternatives to currently used fossil-based ropes in mussel offshore productions.
The analysis of the current context of implementation of biogears in the European aquaculture sector concluded that, overall, current market, technology, social, and policy drivers are promising context for their implementation in the aquaculture sector. (Arantzamendi et al., 2023). Furthermore, the consulted stakeholders would support their implementation regarding their environmental benefits when providing with similar mechanical characteristics.
In TRANSEATION project new biogears with improved mechanical characteristics (to BIOGEARS project) are being developed. To evaluate the efficacy of the low trophic aquaculture infrastructures (longline and rafts) through the implementation of biogears as nature-based solutions (NbS ), the following steps are being undertaken:
References
A rantzamendi L, Andrés M, Basurko OC, Suárez MJ. Circular and lower impact mussel and seaweed aquaculture by a shift towards bio-based ropes. Rev Aquac. 2023; 15(3): 1010-1019. doi:10.1111/raq.12816
BIOGEARS (Grant Number: 863708 ) was funded through EU’s CINEA with EMFF funds of BlueEconomy-2018.
TRANSEATION (Grant agreement: 101135343 ) fund ed under EU HORIZON 2.6- Food, Bioeconomy Natural Resources, Agriculture and Environment. HORIZON-CL6-2023-BIODIV-01