Biogas

Trash To Treasure.

Biogas is a renewable energy composed primarily of methane resulting from the natural decomposition of organic waste by anaerobic bacteria. Landfills and wastewater treatment plants are two major sources of biogas.

Landfill Gas to Energy Illustration

  1. Organic waste material (food waste, non-recyclable paper, diapers, etc.) is placed in the landfill and covered with a layer of topsoil. Anaerobic decomposition of the organic material produces biogas. Biogas is approximately 50% methane.
  2. Biogas flows into perforated pipes inserted into the landfill. Each pipe is connected to the biogas collection system.
  3. A blower aids in extracting the biogas from the landfill.
  4. The biogas is treated to remove water and contaminants that could harm power-generation engines.
  5. Power-generation engines use the biogas as a fuel to turn electrical generators.
  6. The electrical power from the generators is monitored and conditioned before being placed on the electrical power distribution system.
  7. Renewable energy is transported to power users through the existing electrical power distribution system.
  8. Renewable energy is seamlessly available to electric power consumers. Power consumers also generate waste organic material that is eventually  transported to the landfill to complete the cycle of renewable energy production.

Municipal solid waste contains significant portions of organic materials that produce a variety of gaseous products through anaerobic degradation when disposed of in landfills. These landfill gases are primarily comprised of carbon dioxide and methane. Methane is a particularly potent greenhouse gas that, according to the Environmental Protection Agency, has more than twenty times the global warming impact of carbon dioxide.

Landfill gas is required to be collected and flared at many landfills to reduce the risk to public health and safety. A better solution is use the gas to generate electricity. This option has the dual benefit of destroying methane and offsetting the use of nonrenewable energy resources such as coal, oil, and natural gas.

For more info about Landfill Methane : Environmental Protection Agency’s Landfill Methane Outreach Program

Wastewater Digester Gas to Energy

Municipal wastewater treatment facilities utilize a range of physical, chemical, and biological processes to produce a treated effluent suitable for discharge to a receiving stream or reuse in non-potable or indirect potable applications. These treatment processes generate waste solids, commonly known as biosolids or sludge that must be managed and disposed. The source of the sludge is a combination of suspended solids in the raw wastewater (primary sludge) and biomass produced in biological treatment process.

The biosolids streams are often thickened, combined and stabilized in an anaerobic digestion process. The anaerobic digestion process produces a methane-containing gas that can be used to generate electricity, similar to a landfill gas applications. There are more than 16,000 wastewater treatment plants in the United States ranging in size from multi-billion dollar complexes to small, single community plants.

More than 3,500 of these facilities employ anaerobic digestion for biosolids stabilization. Since methane production is one of objectives anaerobic digester design and operation, most treatment plants use a portion of the gas to supply heat needed to optimally operate the digestion process. In most cases, the remainder of the available methane is flared. Presently, only 2 percent of these plants utilize the digester gas to produce electricity. Most of these plants could produce power from the gas and still heat their digesters with the waste heat from the generation process.