From Fish Waste to Omega-3 Concentrates in a Biorefinery Concept

The present work reports a case study for the industrialization of a biorefinery aimed at valorizing fish processing residues in order to obtain ω-3 concentrates for the nutraceutical sector. The biorefinery includes a series of processes: oil extraction from fish waste, fish oil transesterification with ethanol, ω-3 concentration based on supercritical CO2 fractionation. The biorefinery is at first designed and then modeled by Aspen Plus™: this allows for a comprehensive picture (mass and energy flows, processing costs and costs for investment) of the overall process. In accordance with the zero-waste concept, all the biorefinery by-products are valorized: fish proteins as fishmeal, and glycerol, saturated fatty acids and short chain unsaturated fatty acids as liquid biofuel. In addition, fish oil transesterification with ethanol is also experimentally tested in different operational conditions in order to maximize fish oil conversion to fatty acid ethyl esters. A trout processing company located in Trentino Province, Italy, represents the case study. The company produces 870 t/year of fish waste. Mass balances allow estimating a production of 26.6 t/year of ω-3 rich oil (income: 1.3 M€), 160 t/year of fish proteins (income: 0.27 M€), and 160 t/year of liquid biofuel. The biofuel, fed to a 100 kWel CHP unit, allows to produce 720 MWhe/year and 870 MWhth/year, covering the total electricity consumption of the plant and providing more than 45% of the thermal energy needs. This translates into a reduction in utility costs of about 0.12 M€ and avoids the emission of 416 t/year of CO2. Finally, the total investment costs for the whole biorefinery amount to about 3.34 M€. In conclusion, this study demonstrates that the production of ω-3 rich fish oils in a bio-refinery concept could become a good opportunity for valorizing fish by-products and increasing the competitiveness of the fish processing industry.