Development of an Iron-Based Adsorption System to Purify Biogas for Small Electricity Generation Station in Vietnam: A Case Study

In Vietnam, there are about 17,000 pig farms with over 500 pigs, and less than 0.3% of them have a biogas facility. Biogas production from this size is about 50,000 m3/year. This biogas is methane-rich, based on a typical composition of 60–70% methane. However, trace amounts of H2S are also present, which hinder their use as it is very toxic and corrodes the equipment. In this study, an adsorption system using iron-based adsorbent (FeOOH) was developed to remove hydrogen sulfide from biogas at the Thanh Hung pig farm (Thanh Oai District, Hanoi, Vietnam). The initial biogas contained high CH4 concentration of 72%, and the H2S was at the rage of 1995 to about 4000 ppm. Based on the results obtained from the study, it could be seen that FeOOH has high capacity for H2S purification from biogas. The adsorption capacity of the FeOOH was estimated to be up to 0.18 g H2S/g FeOOH. The H2S concentration in the effluent was almost lower than 5 ppm which was suitable for electric generators. In this study, the purified biogas was used for a small electricity generator of 3.5 KVA. As a result, the biogas consumed was about 0.64 m3 per 1 kWh of electricity produced. This amount could fully meet the demand of electricity of a farm. In conclusion, the potential of market for biogas production and consumption in Vietnam is huge. Biogas purification technology for electricity generation, therefore, plays an important role in the biogas market of Vietnam.