การประเมินผลการผลิตก๊าซชีวภาพจากหญ้าขนโดยกระบวนการหมักร่วมกับมูลกระบือ

Abstract

Biogas production is an important technology in the improvement of sustainable energy source schemes that aims to reduce consumption of conventional fuel, therefore reducing greenhouse gas emissions. Biogas production can be accomplished through anaerobic digestion (AD), a biological process which uses biomass as an energy source. In this study, wetland aquatic plant (para grass) and buffalo dung substrates were used for biogas production. These substrates are widely available and hence do not compete with food production. This study focused on the pretreatment methods on para grass and co-digestion with buffalo dung which was divided into 3 parts. The first part was to evaluate raw material pretreatments: thermal pretreatment (hot water 100°C with 2 h) and chemical pretreatment (2%NaOH with 72 hour). The effect of pretreatments on para grass was demonstrated by using scanning electron microscopy (SEM) images. In the second part, efficiency of pretreatment on para grass for biogas production and different ratios between para grass and buffalo dung was performed at a lab scale. The experiment was conducted at room temperature and the highest biogas yield was 12.11 L and the concentration of methane was at 69.30% by using 2% NaOH as pretreatment at 72 residence time. This optimal condition of biogas production was obtained from co-digestion with a 2:1 ratio between para grass and buffalo dung. In the third part, the best ratio was used in the final scale up experiment. Each reactor was made from a 200 L tank with working volume of 150 L. The biogas yield was 1,620.65 L with 69.70% methane. The other objective is to optimize the condition process and develop an engineering/mathematical model. Response Surface Methodology (RSM) can be employed to maximize biogas production. An experiment was used to optimize operational factors. In this case, variables like time, ratio of para grass and buffalo dung were used as the factors on the response of biogas yield. Moreover, heating value of biogas was measured. The heating value of biogas was 39.40 MJ/m3. High heating value (HHV) was 27.80 MJ/m3 and low heating value (LHV) was 25.04 MJ/m3. The volume size was increased to ensure future large-scale applications; and techno-economic process was verified. The result of mass balance analysis suggested that this study apply conservation of mass to the analysis of physical systems. All in all, this study indicated that co-digestion of para grass and buffalo dung was a promising approach in improving biogas production. Also, digestate from the biogas systems containing many macro and micro nutritious can be used as an effective fertilizer.