Fish wastes to omega-3 concentrates in a biorefinery concept

The present work reports a case studio for the industrialization, in Trentino Province, Italy, of a “bio-refinery” aimed at fish oil extraction and fractionation of omega-3 concentrates from trout residues. The bio-refinery is designed and modeled by Aspen PlusTM in terms of two main stages: fish oil extraction from fish residues via the “wet reduction” process, and fish oil transesterification and fractionation to omega-3 concentrates by CO2 “supercritical fluid fractionation” SFF. Together with the main product, i.e. the omega-3 concentrate rich in EPA and DHA, all the other by-products, i.e. proteins, glycerol, saturated fatty acids and short chain unsaturated fatty acids, are separated and valorised. Trout processing produces in Trentino almost 870 t/year of fish wastes, mainly viscera, heads and spines. Detailed mass balances over the optimized oil extraction process lead to estimate the production of 160 t/year of fish proteins and 176 t/year of fish oil which can be efficiently converted into fatty acid ethyl esters (FAEEs) via ethanol transesterification by an optimized procedure developed experimentally in this work. FAEEs are then fractionated by SFF: this process, accurately modelled, allows the production of 13.5 t/y of omega-3 concentrate (87% content in EPA and DHA) and 133 t/y of remaining fish oil (lighter FAEEs). The sale of fish proteins to the market allows to estimate an economic income ranging from 110,000 to 170,000 €/year, while the energetic valorisation of the residual fish oil and glycerol can be performed by means of a 100 kWel high efficiency volumetric engine cogenerating 720 MWhel and 870 MWhth.