A multi-stage biogas upgrading system for household applications: Removal of hydrogen sulfide, carbon dioxide, and moisture using Locally Sourced materials

Abstract

In this work, we aim to study and develop a low-cost multi-stage biogas system for household applications using local materials. The system consisted of three sequential stages: hydrogen sulfide removal using ferric chloride and sodium hydroxide solution–coated clay pellets, carbon dioxide scrubbing with lime water, and moisture control with mangrove charcoal. From the experiments, H₂S can be reduced from over 100 ppm–1.67 ppm to achieve the non-corrosive level for domestic appliances by coated clay pellets. 10 g/L of lime water yielded the highest efficiency (7.84 %) for CO₂ removal. An increase in lime water concentration over 10 g/L diminishes the CO₂ removal due to calcium carbonate precipitation and mass-transfer limitations. In the moisture control stage, the adsorption of mangrove and compressed briquette charcoal is compared; mangrove charcoal exhibited higher capacity and maintained adsorption for ∼110 min, while compressed briquettes reached saturation earlier at ∼55 min. The methane concentration has remained stable in every stage while doing the experiment, with 0.5–1 % of total loss, which is a negligible penalty. The proposed integrated system effectively eliminated H₂S, reduced moisture, and partially removed CO₂, which increased the safety and usability of biogas. While commercial technology (PSA or membrane separation) provides high methane purity and high capital and operation costs. The proposed system offers a more affordable and accessible solution for small-scale rural households. The findings highlight both the feasibility and limitations of using simple, low-cost materials, while future research should emphasize kinetic modeling, CO₂ scrubbing optimization, and long-term adsorbent regeneration to strengthen scalability and reliability.