Characteristics and Nutrient Content of Spent and Non Spent Coffee Ground from Robusta Coffee in Samigaluh, Kulonprogo

Abstract Coffee is Indonesia’s agricultural and foreign exchange source. Robusta coffee is grown and processed dry in Yogyakarta’s Samigaluh District, yielding 40–45% green beans and 55–60% pulp and non-spent grounds. Waste is both an environmental issue and an innovation opportunity. This study examines coffee waste sustainability, particularly coffee grounds and non-spent grounds. Physical and chemical properties will be examined for sustainable agriculture and waste management. The study compares robusta coffee grounds from Samigaluh, Yogyakarta, spent and unspent. SEM measured particle size and morphology, and XRD detected crystalline phases and crystallinity. Walkey, Black, and Kjeldahl measured organic carbon and nitrogen, while wet ashing measured phosphorus and potassium. Analyzing the two coffee waste types required statistics. The average spent coffee grounds are 17.52 microns and the non-spent grounds are 17.97 microns. Spent coffee grounds have 17.8% crystallinity versus 13.4% for non-spent grounds, indicating better physical properties. Even though they contain organic carbon and nitrogen, neither meets organic fertilizer standards without other organic ingredients. Coffee waste is biofertilizer and bio-adsorbent, supporting the sustainable use research goal. Nano-sized particles and mixed compositions should be studied to improve efficacy and usability.