Biogas-to-Energy

Biogas, produced by the digestion of organic materials in waste sites and sewage treatment plants (or farms), has to be collected and combusted. Since it contains about 45-60% by volume methane, it is a valuable fuel for energy production. In general, there are three alternatives for biogas utilization; they are 1) Power production or cogeneration, 2) Direct medium-BTU gas use, and 3) Sale of upgraded pipeline quality (high-BTU) gas. The quickest use of biogas is usually power generation. Power generation by biogas is a mature industry with hundreds of facilities operating throughout the world. The second alternative for biogas utilization is direct burning of biogas. Most of the medium-BTU biogas can be burned in a packaged boiler to generate electricity with a steam turbine or to generate steam for various application. This kind of system has high on-stream reliability and typically the highest use of the heat provided by the biogas. The third project option is to upgrade the biogas to a high-BTU product for injection into a natural gas pipeline. Because of the relatively high capital cost of this option, it may be cost-effective only for those projects with substantial recoverable gas.