Sustainable Production of Coffee Husk Pellets: Applying Circular Economy in Waste Management and Renewable Energy Production

Improper waste disposal is one of the leading causes of environmental pollution, impacting soil, water, and air quality. In coffee plantations, each kilogram of beans produced generates an equal amount of husk, emphasizing the urgent need for sustainable practices to process this residual biomass into valued products. This study aimed to evaluate the potential of coffee husks for pellet production. Three coffee husk types were selected with distinct chemical compositions and granulometries: I (>5.3 mm), II (>2.6 mm and <5.3 mm), and III (<1.77 mm). The biomass was characterized for elemental, structural, and proximate composition. Pellets were produced with two knife heights (15 and 20 mm) and assessed for moisture content, density, length, and mechanical resistance, which were compared with the EN 14691-6 standard (DIN, 2012). Pelletizer productivity was also evaluated. Pellets from biomass III had an ash content of 12.09%, exceeding the <10% requirement. Other treatments met the ash content standard, category B. Pellets from biomass I (17.55%) and II (18.1%) at 15 mm length did not meet the <15% moisture content standard. The remaining pellets met category B standards. Only pellets from origin III (1.62%) met the nitrogen content requirement for international trade (<2%). Pelletizer productivity was higher with smaller granulometry biomass. Coffee husk has demonstrated its potential for pellet production, highlighting the valorization and use of this waste for clean energy generation, contributing to greenhouse gas emissions mitigation, and strengthening circular economy.