Coffee waste: A source of valuable technologies for sustainable development

Coffee, an agricultural commodity principally cultivated in Latin America, South-East Asia, India, and Africa, has exhibited a growing production rate throughout the decades. Through its production chain, different types of waste are generated, which due to their quantity and chemical nature represent an environmental pollution problem. Currently, the strategies applied for proper waste management are designed within the concept of biorefinery to favor sustainable development, within a circular economy. The application and reutilization of such wastes depend on the properties and nature of each constituent. Coffee wastes have been utilized in applications such as animal feeding, enzyme, compost, biogas, and bioethanol production, while novel approaches focus on wastewater treatment, food ingredient replacement, and mimicking materials. Coffee skin, pulp, and parchment (husk) are rich in chemical compounds with relevant bioactive properties. In addition, the polysaccharide content from mucilage allows its exploitation in fermentative processes, whereas the antioxidants and fiber present in silverskin potentiate their use as an ingredient in bakery, dairy, and cosmetic products. Also, spent coffee is a promising material for green energies and sustainable alternatives, which makes the whole coffee process a source of relevant bioactive compounds with several functions. This chapter explores the reutilization of the structural layers of the coffee bean, when discharged as waste. Especial attention is focused on the obtained compounds whose application in the food, pharmaceutical, energetic, materials development, and agricultural sectors allow its sustainable reutilization for different processes.