Towards a circular economy: sustainability assessment of biorefineries for green energy and polyphenolic production from biomass

Pomace is a waste stream that is generated during fruit processing and is regarded as highly polluting due to its high moisture content, biological instability and acidic properties. To facilitate pomace management, the current study has applied the biorefinery concept to develop systems that facilitate value extraction. In this regard, alternative scenarios for the production of polyphenolic compounds and electricity from apple pomace were investigated using ASPEN Plus for process simulations. Scenarios enabling the production of polyphenols using green solvents of subcritical water (scenario (a)) and ethanol (scenario (b)), while also co-producing electricity, were compared to scenario (c) in which the pomace was employed in only electricity production. Comparisons of profitabilities and environmental performances were achieved via a consideration of the net present values (NPVs) and potential environmental impacts (PEIs) respectively, of all scenarios. The study was able to show that scenario (a) constituted the only economically viable strategy, with an NPV of US$19.86 million, while scenarios (b) and (c) were determined to have NPVs of US$-88.12 million and US$-4.05 million respectively. Scenario (b) was also determined to have the poorest environmental performance with a PEI of 148 kPEI/h. Notably, although scenario (c) (PEI of 0.21 kPEI/h) was determined to present a better environmental performance than scenario (a) (PEI of 47 kPEI/h), its economic infeasibility indicated that it will be impractical to consider it as a viable pomace strategy in a future scaled-up system. The present study therefore proposed that scenario (a) may constitute a preferred pomace valorization strategy provided technological innovations i.e. use of renewable energy and gas filters are explored and integrated to reduce the major existing challenge of greenhouse gas emissions. This study provides information regarding the sustainability implications of executing the proposed biorefinery scenarios for pomace management in the fruit processing industry.