Coffee processing waste: Unlocking opportunities for sustainable development

Coffee is the second most consumed product worldwide, cultivated in over 70 countries with an average annual production of 165–170 million bags. Despite the coffee processing methods used, one common research question is about the fate of the wastes generated. Several studies highlight the need for coffee processing waste management, following global calls for climate-smart industrial processing leveraging on reducing the carbon footprint. Various levels of success have been reported in the literature concerning waste transformation into added-value products. Coffee processing waste valorization has been highlighted, including biofuels, building materials, biodegradable containers, organic fertilizer, and value-added compounds production or extraction among others. This review explores opportunities for closing the loop in the coffee value chain concerning circular economy while contributing mainly to seven sustainable development goals. Individual techniques and management practices have been reviewed to propose a scheme for coffee processing waste valorization in a circular economy concept, focusing not only on covering the coffee plantations and processing plants' needs but also on establishing new potential synergies. Thermochemical and biological processes can potentially add further value to coffee waste by facilitating the extraction of high-value compounds. Interest in harnessing these compounds from coffee waste streams continues to grow, highlighting the potential for innovative waste valorization approaches. Despite the data available, gaps still remain in the quest to close the loop and achieve zero waste mainly due to the lack of relative frameworks, regulations, and robust upscaled implementations toward coffee value chain circularity. • Wet processing is preferred due to improved control despite the high waste amounts. • Waste valorization pathways are proposed combining individual published practices. • An integrated coffee waste biorefinery could significantly promote sustainability. • Integrating circularity into coffee processing can transform countries' economies. • A coffee waste valorization scheme under circular context could promote synergies.