Environmental performance and shell formation-related carbon flows for mussel farming systems

This study examined the environmental performance of mussel (Mytilus galloprovincialis) farming in the view of reduction of greenhouse gas emissions, through the Life Cycle Assessment (LCA) methodology. The LCA has been integrated with the evaluation of the carbon sequestration potential of the biocalcification process. Three case studies of mussel farming sited along the coastal area in the north Adriatic Sea, Italy, were analyzed. Two of them concerned mussels that do not require a depuration process (area Class A), and one inspected mussel production in the rearing area of Class B, which imposes a depuration phase after harvesting. This study examined all the relevant flows of materials and energy across the systems and explored the potential role of mussel biocalcification in stocking seawater carbon into the shells. Global Warming (GW) -related emissions amounted to 0.07-0.12 kg CO₂ eq for Class_A case studies and to 0.53 kg CO₂ eq for Class_B case study. Through biogenic calcification, 0.19-0.20 kg CO₂ kg^-1 mussel is fixed in the shells, and 0.12 kg CO₂ kg^-1 mussel is released. These flows resulted in a net sequestration of about 0.08 kg CO₂ kg^-1 mussel. This study confirmed the good environmental performance of the mussel production in the farming systems analyzed. When considering greenhouse gasses emissions, the extent to which the seawater carbon fixed in the shell as calcium carbonate can be considered a carbon sink was discussed and substantiated by locally collected environmental data.