Removing Hydrogen Sulfide Contamination in Biogas Produced from Animal Wastes

Abstract

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. Core Ideas Allophanic soil, brown soil, and black sand almost completely removed H2S at a range of flow rates. Typic sand, raw sand, acidic sand, and podzol soil removed some H2S. Inexpensive filters using local iron‐rich soils can remove H2S from biogas. Used soil in the filters can be easily regenerated by exposure to the atmosphere and reused.

Raw Biogas Desulphurization Using the Adsorption-Absorption Technique for a Pilot Production of Agricultural Biogas from Pig Slurry in Poland

“…In a study [91], the H 2 S removal efficiency was nearly 100% at all gas flow rates for allophane soil, brown soil and black sand, followed by typical sand (about 90-100%). This study showed that selected New Zealand soils with high iron content could potentially be used to build simple and inexpensive H 2 S adsorption beds to improve biogas quality.…”

The role of soils in the regulation of air quality

“…In addition to microbial processes, some chemical and physical processes in soils can remove pollutants. For example, iron-rich soils can be used to chemically remove H 2 S from the gas stream by the formation of iron sulfide [74,75].…”

Cryptogamic Packed Biofilter as Potential Adsorbent for CO2, NH3, and H2S Impurities from Biogas

“…Each filter contained one of the four types of soil (T1, T2, T3, or T4) sieved at less than 400 μm with variable mass (100 g, 150 g, or 200 g); 100 g of biochar (charcoal) dust sieved at less 350 μm; and 545 g of naturally grown moss plant collected from damp sidewalk during the rainy season. The packed bed arrangement of the substrates was adopted from Pham et al [20]; the study demonstrated removal of H 2 S using local soil materials from biogas produced by anaerobic digestion of animal wastes. In this study, 700 g layer of small and medium gravels was added above the aerator to prevent blockage by overlying filter material.…”