Integração energética da produção de biogás a partir dos resíduos da produção de café

Abstract

This study determined biogas production from the anaerobic digestion of coffee mucilage to evaluate the biochemical methane production potential with an evaluation of proposed environmental scenarios using coffee production waste (mucilage and process wash water), aerobic treatment plant sludge, and swine whey. The proposition of the scenarios was based on the survey of data previously available in the literature and on experimental tests using coffee mucilage. The specific methanogenic activity (SMA) of mucilage was determined in 500 mL flasks and the volume of biogas produced was determined by the volume shift method after washing in alkaline solution. The presence of nutrients and pH were parameters of analysis in the experimental evaluations. The results obtained experimentally showed that pH was the parameter with the greatest influence on biogas production. From the experimental tests, three scenarios were proposed aiming at the integration of energy generation from coffee waste (scenario 1) with other substrates from the region, such as aerobic sludge (scenario 2) and whey (scenario 2). That of the coffee mucilage was 804NmlCH4/gSTV when the pH was corrected to 6.5. The PMB of the coffee bean processing wash water was estimated theoretically by the ratio of 0.35L CH4/g COD removed, resulting in 0.087NLCH4/gSTV. The theoretical estimates for the scenarios showed potential for energy utilization: for the base scenario, composed of coffee waste only, resulted in the production of 4,919.31 m3CH4, equivalent to 145.657,15 MJ of thermal energy and 16,188.28 KWh of electrical energy per harvest period, and could supply coffee drying stages a 11% in coffee production time. For scenarios 1 and 2, the results showed the alternative use of waste in the off-season, because the energy production was the same for both sludge and whey, in this period it could supply 31 households in the off-season time.