Abstract
Coffee pulp waste composition consist of cellulose, hemicellulose, lignin, pectin and caffeine, tannin, and polyphenol as inhibitor substance. The high cellulose compound in coffee pulp can be used for alternative raw materials in the manufacture of biogas. This study aims to define the composition of the mixture of microorganisms of Pseudomonas putida, Trichoderma harzianum, and Aspergillus niger that are best to use in coffee pulp pretreatment to degrade inhibitor substance. The best result of pretreatment will be applied to biogas production. The first step is to do a pretreatment of the coffee pulp with variable Pseudomonas putida : Trichoderma harzianum : Aspergillus niger with a ratio of 1:1:1, 1:2:1, 1:1:2, 1:2:2, 2:1:1, 2:1:2, 2:1:1 (v:v:v), then variables that are most excellent in degrading inhibitor substance are selected. The second step, is doing anaerobic fermentation for 20 days at mesophilic temperature (30-40°C) on a reactor working volume of 4.5 L. In the making of biogas, a varied starter as much as 10% of the total are put into the reactor in the form of a mixture of cow dung : rumen fluid with a ratio of 1:0, 0:1, 1:1, 1:2, 2:1 (w/v). The parameters measured include the decreasing of the inhibitor substance, Chemical Oxygen Demand (COD), biogas (CH4 and CO2) and calorific value of combustion (Heating value). This study results a composition of ingredients within the pretreatment process which includes a mixture of microorganisms with a ratio of Pseudomonas putida : Trichoderma harzianum : Aspergillus niger is 1:2:1 (v:v:v). For biogas, a mixture of cow dung and rumen fluid can produce higher methane gas is the ratio of cow dung : rumen fluid is 1:2 (w/v) with the concentration of methane (CH4) formed at 1.825%. At the concentration of methane is 1.825%, the heating value obtained is 76.032 kcal/kg with volume biogas 0.0032 m3/ kg converted of COD.
Highlights
One of the many industrial waste obtained from processing coffee beans include coffee pulp
In bioreactor 1, with addition of Pseudomonas putida, Trichoderma harzianum, and Aspergillus niger with ratio 1:1:1, at the end of process caffeine was decreased from 0.86% become 0.04%, tannins was decreased from 4.81% become 0.05%, and polyphenol was decreased from 3.48% become 0.07%
In bioreactor 2, with addition of Pseudomonas putida, Trichoderma harzianum, and Aspergillus niger with ratio 1:2:2, at the end of process caffeine was decreased from 0.86% become 0.005%, tannins was decreased from 4.81% become 0.01%, and polyphenol was decreased from 3.48% become 0.0011%
Summary
One of the many industrial waste obtained from processing coffee beans include coffee pulp. Some substances within coffee pulp contains inhibitor, such as caffeine, tannins, and polyphenols which are able obstruct the production of biogas [1]. Degradation of the toxic material contained in coffee pulp such as caffeine, tannins and polyphenols, can be executed by the use of microorganisms [1]. Several microorganisms can degrade Tannins, fungi species have a specialty in degrading tannins such as Chaetomium, Fusarium, Rhizoctonia, Clyndrocarpon, and Trichoderma harzianum [4] and microorganisms that can degrade polyphenols such as Aspergillus, Fusarium, Coprinus, Penicillium and the highest degradation rate is Aspergillus niger of 8 mg/L/h It can be analyzed in previous research that Pseudomonas putida, Trichoderma harzianum, and Aspergillus niger have special ability to degrade each inhibitor substance. The three selected microorganisms to degrade the inhibitor substances as a variable in degrading inhibitor substance and applied in the manufacture of biogas
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