Portable anaerobic bioreactor design and production trials

Abstract

Biogas is a flammable gas mixture that can be produced by anaerobic digestion of organic wastes. It contains 50-65% methane gas, 35-50% carbon dioxide (CO2) gas and 100-1000 ppm hydrogen sulfide (H2S) gas in biogas. One of the biggest disadvantages in biogas production technologies is the cost of purification technologies that convert biogas to biomethane. In this study, a portable, intermittent anaerobic bioreactor and a 20 liter gasometer were designed. The purpose of using gasometer is to ensure the adsorption of H2S and CO2 gases in the raw biogas coming out of the bioreactor, using only the production power of the biogas without requiring any external intervention. In this context, only the produced biogas amount and biogas content of the batch bioreactor with an effective volume of 5 liters were tested twice. Within the scope of this production, a sample was taken every five days from the start of gas production in the batch reactor and the removal of chemical oxygen demand was compared with the initial situation. Each production trial lasted 36 days. Then, the second stage of the study was started and the biogas outlet was directly connected to the gasometer tank. At this stage, biogas and organic waste samples were taken from the gasometer and batch reactor every five days and tested. While the H2S and CO2 contents of the biogas formed as a result of the experiments without gasometer were 558 ± 55 ppm and 55.4 ± 2.9%, respectively, these values were found to be 45 ppm and 24.5%, respectively, as a result of the production with gasometer. As a result, it has been determined that an industrial-scale gasometer system adsorbs approximately 88% of H2S and 55% of CO2 in biogas without requiring an extra biogas purification unit. For further studies, changing the gasometer volume and increasing the holding times of the water in the gasometer are recommended as CO2 and H2S concentrations can be further reduced.