Waste-to-energy: Biogas potential of waste from coffee production and consumption

The generation of waste is a necessary process related to the production and consumption of coffee. One of the wastes associated with the production of coffee is the husk, which separates from the beans when it is roasted. The waste from the consumption of coffee is spent coffee grounds generated during the coffee brewing process. The study aimed to determine the possibility of coffee production and consumption waste conversion in the anaerobic digestion process. The tested parameters were, among others, biogas efficiency, methane efficiency, and methane content in biogas. The experiment was conducted under anaerobic digestion conditions using DIN 38414/S8 norm. The total solids content of the coffee husk was 93.37%, with the organic matter content at 93.34%. The biogas efficiency in terms of fresh matter was 329.50 m3‧Mg−1. The total solids content of all three analyzed grounds samples ranged from 41.27 to 45.72%. The high volatile solids content, in the 97.91–98.41% range, confirmed the biogas potential. In all three samples of coffee grounds, biogas efficiency was in the range of 225.45–270.97 m3‧Mg−1. The obtained results allow concluding that analyzed coffee production and consumption waste have a high potential for biogas production.