Removing Hydrogen Sulfide Contamination in Biogas Produced from Animal Wastes

Hydrogen sulfide (H2S) contamination in biogas produced from animal wastes limits its use to cooking and precludes it from being used for heating, lighting, or electricity generation. This limitation results in the release to the atmosphere of between 3 and 51% of total biogas produced. Biogas contains 50 to 70% methane (CH4), a potent greenhouse gas that contributes to global warming. This study aimed to develop a cost-effective H2S filtering system using local materials rich in iron as iron oxide (Fe2O3), which reacts readily with H2S and forms adsorbed iron sulfide (Fe2S3) when gas is passed through it. Here we tested the performance of seven New Zealand soils and sand, each at five different gas flow rates (59, 74, 94, 129, and 189 mL min(-1)). We found that three materials (allophanic soil, brown soil, and black sand) had stable H2S removal efficiencies close to 100% at all gas flow rates, followed by typic sand (89-99%), raw sand (76-99%), acidic sand (48-89%), and podzol soil (58-87%). These results show that inexpensive and simple filters to remove H2S from biogas can be made using local soils. Used soil in the filters can then be easily regenerated by exposure to the atmosphere and reused to achieve sustained H2S removal efficiency.