Apple pomace biorefinery: Integrated approaches for the production of bioenergy, biochemicals, and value-added products - An updated review

The apple (Malus domestica) is one of the most consumed fruits worldwide. However, its processing by the juice industry generates approximately 4 million tons per year of apple pomace. Therefore, the agri-food industry must apply waste management technologies to reduce the environmental impacts caused by the incorrect destination of the solid residues. In this sense, this review addressed an update on the novel technologies for producing value-added products and bioenergy in a novel apple pomace biorefinery. Currently, the most common desti-nation of apple pomace is for animal feed and composting. However, if not managed properly, it can cause serious environmental pollution. Recent strategies on the integrated biorefinery approach could explore the application of anaerobic digestion to produce bioenergy (methane and hydrogen) and organic fertilizer. More-over, the apple pomace can be turned into various bio-products using green technologies (microwave, ultra-sound, supercritical fluids, and pressurized liquids) for extracting bioactive compounds (p-coumaric, chlorogenic, ferulic, quercetin, quercetin-3-O-diglucoside, quercetin-3-O-galactoside, and epicatechin). Finally, this review contributes to adopting integrated biorefineries for the apple processing industry, reintroducing the apple by-product in bioprocesses for food, feed, pharmaceutics, cosmetics, and bioenergy production, in a cir-cular economy framework.