Environmental insights of bioethanol production and phenolic compounds extraction from apple pomace-based biorefinery

Abstract

Food waste is one of the main challenges of solid waste management throughout the food supply chain. Apples are one of the most widely consumed fruits worldwide, the production of which is accompanied by the generation of pomace as a by-product with valuable nutrients. This research presents the first environmental insights of a multiproduct apple pomace-based biorefinery through a life cycle perspective. The design and process modelling of this platform aims to produce bioethanol and extract total phenolic compounds (TPC) towards an efficient use of the pomace obtained from the apple manufacturing industry (juice production). Bioethanol production consist of pressing, fermentation, distillation as the main processes; while in the case of TPC, two extraction techniques were evaluated: i) solvent extraction (mainly water), and ii) the Soxhlet method. The life cycle analysis followed an attributional cradle-to-gate approach considering different midpoint impact categories from the ReCipe 2016 method such as Global Warming (GW), Eutrophication, Human Toxicity, Fossil Scarcity, among others. The results indicate that bioethanol production encompasses a GW profile of 3.17 kg of CO₂ eq per kg of product, being the vinasse treatment (subproduct after distillation) the most impactful stage. Phenolic compounds extraction with water achieves a total value of 5.8 kg CO₂ eq per g of TPC, while 0.22 kg CO₂ eq per g of TPC is obtained with Soxhlet technique. Furthermore, a sensitivity analysis is addressed to improve the environmental profile of bioethanol and TPC. This research demonstrated the relevance of process design on the environmental performance of bioethanol and TPC, where stillage treatment has a key contribution to the results and the use of solvents in TPC extraction, although improving extraction yield, leads to a higher environmental impact.