Improving the stability and simultaneously capturing CO₂ during biogas production under controlled internal pressure using NaOH

The current phenomena in research is coupling the digestion process and cleaning stage in one compartment with an aim of suppressing gas cleaning and energy costs. To improve the stability of the digester two concentrations of NaOH were tested in a batch pressure digester at the pressure of 6 bar. Significant amount of biogas and methane gas were recorded, both cumulative and daily. The highest amount of biogas was recorded when the system was buffered with 2.66 M NaOH solution, followed by the one without NaOH in daily productions. Cumulatively the amount of biogas produced when the system was buffered with 5.33 M NaOH appeared to be higher than amount of biogas produced with buffer. In this study, the methane composition at 0 M NaOH, 2.66 M NaOH and 5.33 NaOH were 71.2%, 76.9 and 78.8%, respectively. Using 2.66 M NaOH buffer the system was more stable as evidenced by the amount of biogas produced.