Optimizing the processes of extracting proteins from yellow peas and ethanol production from spent pea residues

By considering neutral and alkaline extraction processes, this study aimed to maximize the yield and quality of a protein isolate from yellow peas while minimizing minimum selling price (MSP), then investigate the feasibility of integrating ethanol production from the starch in the spent pea residue from an optimized protein-extraction process. Thus, response surface methodologies were used to optimize experimental measurements and industrially simulated outcomes (Aspen Plus®) from variations in pH, temperature, time and solid loading. Then the energy and stream integration of ethanol production were simulated and costed. Alkaline extractions optimized at pH 10, 20 °C, 100 min and a 5.3% solid loading resulted in a protein yield of 73.6% and MSP of 3.25 US$/kg, at a processing rate of 2000 kg/h. These outcomes were technically and economically superior to water extractions, which only obtained a maximum protein yield of 56.2% and lowest MSP of 3.52 US$/kg. The output of ethanol integration was 8 million litres per annum, but further capital and energy demands of 230% and 126%, respectively, increased the MSP of the pea protein to 4.58 US$/kg. Sensitivity analysis showed that process changes, larger scales and incentives for renewable fuels are needed to favour the integration of ethanol.