Zero-Waste Processing of Protein Rich Side-Streams

This study evaluates possibilities of complete exploitation of selected high protein and high oil containing industrial co-streams by applying environmentally benign biomechanical processing technologies. Value components for food and skin care products are main focus. Remaining residue is simultaneously exploited for soil improvement. Rapeseed and fish processing co-streams have been chosen as raw materials, as they have high enough quality for food applications.

The quantities of these side-streams are significant. For example, if the volume of the co-stream from Norwegian salmon aquaculture is 275 000 t annually, there are 55 000 t of lipids and 41 000 t of proteins available. Likewise if 270 000 t of rapeseed press cake is produced by SME cold pressers in Germany, there are 27 000 t of lipids and 95 000 t of protein available for refining.

This study presents three developed process concepts for zero-waste processing of food side-streams: (i) thermo-enzymatic process for recovery fish oil and protein hydrolysate from fish side-stream, (ii) enzymatic process for fractionating proteins and peptides from rapeseed press-cake, and (iii) co-generation of heat and fertilisers out of residue from previous processes, namely fish bones, hulls or solids from hydrolysis.

The main emphasis of this study is to evaluate techno-economic feasibility of proposed process concepts. Mass and energy balances of concepts are estimated, raw material demand, utilities used and intermediates or products produced are calculated and variable production costs are evaluated. In addition, rough estimates for the fixed operating costs and investment costs are given. Finally, a profitability analysis is conducted based on the variable costs and fixed costs.

As the degree of uncertainty is high at early stages of process design, Monte Carlo simulation are applied when estimating variable and fixed costs in order to cope with this uncertainty. By applying this methodology, ranges and distribution can be used for the main process parameters, prices and also for investment. As a result of calculations, a probability distribution of outputs, e.g. profit, is obtained.