Performance of Biogas Production from Coffee Pulp Waste with Cow Dung and Cattle Rumen Fluid as Inoculum in a Batch Reactor

Production of biogas from coffee pulp waste is one of the potential attempts to provide alternative energy in Indonesia. As a leading commodity in Indonesia, the coffee produced the residual waste from its processing such as the pulp waste (include the exocarp, mesocarp, and endocarp). The waste contains the toxic agent such as caffeine, tannin, and free phenols which can inhibit the biogas production. Therefore, in this study, the biological pretreatment using civet feces ( Paradoxurus hermaphroditus ) was performed. The performance and kinetic of biogas formation from the coffee pulp (with and without pretreatment) using cow dung and a mixture of rumen fluid and cow dung as inoculum have been investigated. Biogas production was done anaerobically for 40 days at mesophilic temperature (37  o C) in a reactor with a working volume of 3.6 liters. Measured parameters included the inhibitor components, TS, VS, COD, production of biogas, and kinetic parameters. This study reveals that the pretreatment using civet feces could reduce the inhibitor compounds in the coffee pulp waste leading to produce methane in higher concentration than those without pretreatment. The digester containing pretreated coffee pulp with cow dung and rumen fluid addition showed the best performance of biogas formation. Kinetic parameters which were obtained from the fourth digester were k (0.0446 day -1 ), Y (0.056 g cells/g substrate), μ m (0.0688 day -1 ), K s (25.2359 g/L), and y m (43.299).