Journal of Environmental Analytical Chemistry

The trace amount of carbon dioxide and hydrogen sulphide in raw biogas lowers its calorific value, causes corrosion and makes it hard to compress the biogas into cylinders. Raw biogas was obtained from anaerobic digestion of cow dung and market wastes. The gas was stored in tubes or urine bags before upgrading process. Eburru natural zeolite rocks were used as the upgrade materials. The measured initial level of raw biogas was 0.0227% H₂S, > 20% CO₂ and 52-56% CH₄. The total removal using zeolite was observed to be 75% CO₂ and 95.34% H₂S leading to 83.45 – 91.23% methane levels. The morphological structure of zeolitic rocks accounted for its higher upgrading properties. In addition, the porosity in these rocks meant that CO₂ and H₂S were adsorbed resulting in higher CH₄ levels in the upgraded biogas.