Industrial energy demands are rapidly outpacing the available fossil fuel sources, and the need for alternative energy sources is widely recognized. Experts have proposed biogas as one of these new sources. Biogas is a combustible mixture of gases produced from the anaerobic digestion of organic material by a community of microbes. Biogas is naturally produced in large quantities by landfills and waste-water treatment plants. Many farms worldwide have invested in anaerobic digesters to produce small quantities of biogas from organic waste. Because of the wide availability and renewable nature of the organic materials and microbes required for biogas synthesis, biogas is a potentially effective and sustainable energy source. Compared to natural gas, biogas production, processing, and use generate lower greenhouse gas emissions.
Current methods of biogas purification involve chemical or mechanical processes, including chemical scrubbing, chemical adsorption, filters, and membranes. These are expensive and often environmentally hazardous due to the nature of the chemicals. Problems associated with cost and sustainability prevent biogas from becoming a competitive alternative energy source.
Biological methods of purifying biogas exist but are not used on an industrial scale. Photosynthetic algae and a few other autotrophic microbes metabolize CO2 to produce sugars and other compounds that can be used as biofuels. Other microbes, such as purple and green sulfur bacteria, consume H2S during metabolism and produce solid elemental sulfur. These microbes can be used in a system that removes CO2 and H2S impurities from biogas. Because these microbes are self-sustaining and renewable with minimal nutrients, a biological system may be more sustainable and cost-efficient.
Below is a model of our implementation: