Abstract
Coffee is widely regarded as one of the most popular beverages globally, due to its availability, health benefits, and consumer preferences. Nevertheless, the whole process from coffee production to consumption generates nearly two billion tons of solid waste annually, with coffee husk accounting for approximately ten million tons of that waste. Coffee husk is considered the primary co-product generated during the dry processing of coffee, and most of it is directly disposed of in landfills. The mismanagement of coffee husk leads to environmental pollution, impacting both coffee production and its sustainability. Thus, the sustainable utilisation of coffee husk is essential for promoting a circular economy and reducing environmental pollution. In this case, utilising coffee husk for low to moderate added-value products or extracting bioactive compounds for high-value products presents an innovative approach to promoting sustainability. This strategy could enhance the value of coffee husk while contributing to environmental sustainability. However, this review largely emphasises the key bioactive compounds in coffee husk, along with their extraction methods, functional properties, cytotoxicity, digestibility, and various applications. The findings of the current review elucidated that coffee husk extract contains bioactive compounds with strong antioxidant, antimicrobial, sensing, and biocompatibility properties. These qualities enhance digestibility and gut microbiota, providing health benefits and potential applications in food, pharmaceuticals, and biomedical fields.