Carbon Dioxide (CO2) Reduction of Tofu Industrial Waste Water-Based Biogas by an Integrated Process of Activated Carbon and Zeolite Adsorption to Enhance Pipeline Quality Gas

Biogas is a renewable alternative energy source derived from anaerobic degradation of organic materials. The main contents of biogas are CH4 and CO2. Methane in biogas has been developed as energy source, the higher CH4 content in biogas, the better its quality. In Indonesia, biogas from tofu industry waste water is a potential energy source. The tofu waste water contains organic matter as COD (Chemical Oxygen Demand) ranged between 7,500-14,000 mg/l. Anaerobic digestion process can produce biogas composition as follows: 45.89% of CH4, 29.69% of CO2, 0.33% of H2S, 0.0006% of NH3, and 24.10% of H2O. This study focused on CO2 and H2O reduction because both components are the highest impurities. The H2O removal was using condensation process, and the CO2 was removed by integrated adsorption using activated carbon and zeolite. Biogas feed volumetric flow rate was varied by 0.15 m(3)/s; 0.21 m(3)/s; 0.30 m(3)/s, meanwhile the space time was varied by 1 h, 2 h, 3 h, 4 h, 5 h. The best H2O and CO2 removal was given at flow rate of 0.30 m(3)/s and flow time of 2 h, the removal efficiency were 99.80% and 97.22%, respectively. It could give result of CH4 content in biogas of 99.55%. The high purity of the CH4 met the criteria of pipeline quality gas.