Abstract. Organic waste, fruit waste and vegetable waste are the best substrate to produce biogas. Waste management system for producing biogas can be used as a solution with the waste problem by converting the wastes into biogas. This study is expected to review of the effect of substrate type and substrate composition for the volume of biogas produced. In this study, materials consist of fruit wastes (oranges, apples, papayas, and tomatoes), cow ruminant, urea, cow dung, Na 2 CO 3 buffer, NH 4 HCO 3 buffer, and distilled water with variations of the substrate materials, F/ W, and the buffer types. The addition of cow manure and Na 2 CO 3 buffer with 1:2 of F/W, production of biogas is greater than variable which is used NH 4 HCO 3 buffer and without the addition of cow dung. Variables with addition of cow dung with 1:1 of F/W and using Na 2 CO 3 buffer, the result is greater than the variable using the same buffer but without the addition of cow dung and variables with 1:1 of F/W with the addition of cow dung and Na 2 CO 3 buffer and variables with the same feed and without the addition of cow dung produce more biogases than variable which is the using NH 4 HCO 3 buffer, 1:1 of F/W and without the addition of cow dung.

Abstract. The result of this research is to determine the ratio of the combination of cow manure and bagasse (F/I) to the volume of biogas production, chemical pretreatment effect of raw material bagasse on biogas production volume and the effect of co-digester on biogas production. The results showed a decrease in total solid occurs when the increase of 2%, 5% to 10%, and this contributes to decreasing the production of biogas. Chemical pretreatment influences on the production of biogas through pretreatment with 2% NaOH solution with surface morphology bagasse seen with SEM image and its chemical structure changes with FTIR instrument. The highest biogas yield of 51.04 L/Kg substrate was obtained from a combination bagasse treated with 2% NaOH solution for 24 hours and as much as 20% cow's rumen.

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Abstract. Rice husk is one of agricultural waste generated from the mill is potential to be converted to biogas. Otherwise, biogas production facing problem due to the high lignin content. This research is objected to study the effect of enzymatic pretreatment and C/N ratio to biogas production from rice husk by solid state anaerobic digestion (SS-AD). The laboratory scale-anaerobic digestions was used in this work. It is operated in batch system and with room temperature. Total solid (TS) was set 21%. Enzymatic pretreatment was conducted using lignase enzyme. Carbon to Nitrogen (C/N) ratio was varied from 20, 25, 30, and 35. The C/N ratio is varied by adding some quantity of technical urea to the substrate. Biogas formed was measured using water displacement method in every two days. The result showed that enzymatic pretreatment could increase biogas production from 30 to 55 %. The highest biogas production was obtained at C/N ratio 35. Specific biogas production on C/N ratio of 20, 25, 30, and 35 were respectively 12.0, 12.6, 13.5 and 18.2 ml/gr TS. The volumetric loading resulted by SS-AD was higher than liquid anaerobic digestion (L-AD). The further research need to conduct for optimization the enzyme concentration and C/N ratio.

Abstract. Rice straw is agricultural waste containing high potency to be treated to biogas. However, the usage of rice straw is still limited due to high lignin content that will cause low biodegradability. The aim of this research was to study the effect of pretreatment using NaOH and acetic acid to biogas production from rice straw. NaOH was varied from 2%w, 4%w, and 6%w; and acetic acid was varied from 0,075 M, 0,15 M dan 0,75 M. The rice straw was cut into 1 cm size and submerged for 30 minutes in NaOH and acetic acid solution. The rice straw then filtered and neutralized before sending to anaerobic digestion process using rumen fluid bacteria. Biogas produced was measured using water displacement method. The result showed that the optimum concentration of NaOH solution was 4%w that resulted in biogas volume of 21,1 ml/gTS. Meanwhile, the optimum concentration of acetic acid pretreatment was 0,075 M that produced biogas volume of 14,5 ml/gTS. These results suggest that pretreatment using NaOH solution is more effective for decreasing the lignin content from rice straw.