Valorização dos resíduos de café para obtenção do biogás

Abstract

Coffee The coffee production in Espírito Santo plays a crucial role in the local economy, being fundamental for the agricultural and financial development of the region. As Brazil's second-largest coffee producer, the state contributes over 30% of the national production, with significant outputs of both Arabica and Conilon. The by products generated, such as coffee grounds and husks, represent a valuable opportunity for energy production. However, the challenge lies in maximizing the utilization of these by-products, which are notable not only for their quantity but also for their rich composition of organic matter and lipids, essential elements for methane production. The valorization of these residues through anaerobic digestion is promising, offering a sustainable disposal method and generating useful by-products, such as biogas for electricity production and organic fertilizer. However, anaerobic digestion faces challenges related to nutrient balance, composition, and complexity of high molecular weight organic molecules. One way to address these issues is by pre treating the organic matter to increase biodegradability and bioavailability of the molecules and performing codigestion to balance nutrients. In this context, this study assessed the biochemical potential of methane (BMP) from domestic coffee grounds (both treated and untreated) and industrial coffee husks (both treated and untreated) in combination with food waste (codigestion). Sludge from a wastewater treatment plant (WWTP) was used as the inoculum. Duplicate batch anaerobic reactors (250 mL) were fed with substrates in different proportions, using a substrate/inoculum ratio of 1. BMP tests were conducted on average for 20 days at mesophilic temperature (35±2 °C). The highest BMP levels were detected with 50% treated coffee grounds (400 NmL/gSV), 50% treated coffee husks (344 NmL/gSV), and 100% food waste (600 NmL/gSV). On the other hand, 100% coffee grounds or coffee husks showed low BMP percentages (88 NmL/gSV) and (186 NmL/gSV) respectively, due to low carbon/nitrogen ratios and pH outside the ideal range. These results indicate that coffee residues have potential for energy recovery through anaerobic digestion (AD), highlighting AD as a promising alternative for the valorization of these residues