Energy analysis in fish aquaculture: cumulative energy demand of different farming systems

Energy consumption is one of the critical challenges for the continued growth of the aquaculture sector. In addition to the substantial feed consumption common to all types of systems, the high direct energy demand is driven by electricity use for water extraction, pumping, and aeration in land-based farms, and by fuel consumption in coastal farms. The aim of this study is to analyse the Cumulative Energy Demand (CED) of the production of European Sea Bass and Gilthead Sea Bream across different farming systems in the Mediterranean area. By focusing on both land-based and coastal sea-cage systems, an energy analysis of four different farms was conducted using a “from cradle to gate” life cycle approach. The functional unit for this study was set at 1 tonne of fish. The results show that land-based farms have a higher CED (168,535 and 188,642 MJ/t) due to both feed consumption (32 and 39 % of the total) and the use of liquid oxygen (46 and 16 % of the total) and direct electricity (20 and 43 % of the total, with on-site electricity consumption of 34,167.6 and 14,086.8 MJ/t). The lower CED of coastal farms (66,224 and 76,507 MJ/t) is largely due to feed usage (around 90 % of the total) and low fuel intensity (67.6 and 82.9 l/t, corresponding to 2495 and 3057 MJ/t, respectively). A scenario analysis was conducted using the 2030 projected national electricity mix of the Integrated National Energy and Climate Plan for land-based farms. Additionally, the impact of substituting diesel with biofuel in coastal farms was evaluated. The results indicate that these changes could reduce the use of non-renewable sources by at least 5 %.