Although biogas is clean and environmentally friendly, its existence is often unsustainable, especially in rural area. Consumption of fossil fuel energy still dominates because cheaper, higher in energy efficiency and ready to use than biogas. One of the efforts to make biogas can compete with fossil fuel energy is by increasing calorific value. Reduction of carbon dioxide by adsorption enhances the calorific value that evidenced by methane enrichment. In this study, we investigated the effect three types of combined adsorbent: pure natural zeolite (Z-Z), zeolite-biochar from chicken manure (Z-B1) and zeolite-modified biochar (Z-B2) on methane content. The result showed that adsorption of biogas using Z-Z, Z-B1 and Z-B2 increased methane level with enhancement of 1,36; 28,92; and 11,27% respectively compared before adsorption. To confirm whether these results were influenced by adsorbent’s character or not as consequence adsorbent characterization have been done in this study.

The utilization of the recycling of biomass waste for carbon dioxide (CO2) adsorption in biogas is still rare. Even though the experiments on the biogas purification still using synthetic biogas. This paper investigated the recycling of biomass waste, sugarcane bagasse for biogas purification. The conversion of biomass into biochar was claimed to expand the surface area of its pores for capturing CO2 in biogas. Five treatments of adsorbents used in this study, 100% volume of zeolite or biochar, 75% volume of zeolite and 25% biochar, 50% volume of zeolite and biochar, 25% volume of zeolite and 25% volume of zeolite, and 25% volume of biochar. The difference of volume treatment in adsorbents affected methane (CH4) and CO2 composition of biogas. Biogas purification by adsorption was conducted at 5-7 bar pressure range and room temperature. Biogas before and after purification were tested of CH4 and CO2 composition by gas chromatography. A significant reduction in CO2 was shown when 50% volume of zeolite was replaced by biochar. The highest in CO2 reduction showed by the composition of 50% sugarcane bagasse-based biochar and 50% natural zeolite. The CO2 decreases did not accompany by the CH4 increases because mesopore-sized still dominated the adsorbents’ pore size.

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We evaluated the adsorption of CO 2 in biogas mixtures using the combination of adsorbents: natural zeolite-natural zeolite (Z-Z), natural zeolite-chicken manure based biochar (Z-CM) and natural zeolite-biogas sludge based biochar (Z-BS). The amount of CO 2 adsorption was controlled at room temperature and under a gas pressure range of 5-7 bar. Samples of biogas before and after adsorption were analyzed by gas chromatography (GC) to determine the percentage of CH 4. The relationship between the percentage of CH 4 composition and calorific value of biogas was investigated. The results of data from GC showed that the highest CH 4 enrichment was performed by Z-CM (28.92%). The highest CH 4 enrichment increased the calorific value of biogas in comparison to biogas before adsorption. The result suggested that CO 2 adsorption using natural zeolite and chicken manure based biochar successfully increased the calorific value of biogas.

Rice husk-based biochar has been prepared by pyrolysis process for carbon dioxide adsorption in biogas. Biochar is considered as porous material for carbon dioxide adsorption. In this study, the adsorption of carbon dioxide, the largest impurity in biogas, was evaluated. The adsorptions were conducted in five treatments (mass variation): 80 grams of biochar (RB1), 60 grams of biochar and 20 grams of zeolite (RB2), 40 grams of biochar and 40 grams of zeolite (RB3), 20 grams of biochar and 60 grams of zeolite (RB4), 80 grams of zeolite (RB5). The best performance of carbon dioxide adsorption showed by RB1 with the decrease in carbon dioxide up to 31.59%. Characterization of adsorbents were also investigated by surface area analyzer to know relation between surface area and adsorption capability. It was found that the larger surface areas are favorable to adsorb carbon dioxide.