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Green Energy from Waste: How Biogas Can Help Plants Save Money- and Save the Planet

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April/May 2016

Environmental commitments, the rising costs of water and energy, and the desire to be more self-reliant are all factors motivating municipalities, industries, and farms to invest in alternative energy sources. Renewable biofuels such as biogas can help secure energy and save money—all while helping protect the environment.

What Is Biogas?
Biogas is a biofuel that is produced through contemporary biological processes, such as the anaerobic digestion of wastewater. Anaerobic wastewater treatment is a biological process that takes place in the absence of oxygen. As organic matter breaks down, biogas made up of approximately 60 to 70 percent methane is naturally released.

Methane is a greenhouse gas much worse than carbon dioxide (CO2). When wastewater treatment tanks and lagoons are left uncovered, greenhouse gas emissions enter the atmosphere, damaging the ozone layer and, consequently, human health. Capturing this by-product of wastewater treatment can benefit the environment and the bottom line.

The Benefits of Biogas Recovery
Biomethane is arguably the most energy efficient biofuel, and one of the fuels with the lowest impact on the environment. It can be used in engines and combined heat and power (CHP) units for electricity and heat, and in boilers for process heat and steam. Benefits of biogas recovery include:

  • • Increased energy security
  • • Reduced energy costs
  • • Income potential
  • • Take advantage of government green energy incentives
  • • Sell extra energy
  • • Smaller carbon footprint
  • • Less harmful emissions
  • • Improved air quality
  • • Odor control

Capture Biogas
The first step to reaping the benefits of biogas is to capture this valuable resource.

A gastight membrane cover, such as those engineered by Geomembrane Technologies Inc. (GTI), is the best way to contain the biogas produced by anaerobic digestion. The waste-to-energy cover should be made with strong, long-lasting materials to resist tears, punctures, chemicals, and ultraviolet rays. An insulated cover design will help maintain consistent temperatures throughout the anaerobic process, so even less energy needs to be produced. To make routine maintenance and sampling easier, look for a cover that is safe to walk on and that has built-in hatches and ports to simplify access to mixers and other equipment.

Safely Control Biogas
To protect your waste-to-energy investment, a biogas control system is recommended. This system protects the cover from damage and safely delivers biogas into a pipeline for renewable energy conversion or disposal to a flare. A biogas control system regulates the withdrawal of biogas from underneath the cover, supplies the gas at the appropriate pressures, and controls sediment and moisture in the gas.

For safety reasons, it is very important that the system maintains a consistent vacuum by removing biogas at the same rate as it is generated. Consider emergency vent stacks, safety valves, and moisture traps. Other biogas safety considerations include:

  • Ability for the cover and biogas control system to withstand corrosive gases
  • Real-time remote monitoring capabilities
  • Alerts or alarms to notify operators of unsafe conditions

Be sure to consult a biogas expert to help commission your waste-to-energy project so they can review safety precautions and provide advice on how to maximize the use of biogas.

Store Biogas
Gasholders allow treatment plants to safely store excess biogas for later use. They regulate and respond to fluctuations in biogas volume, and typically range in size from 1,800 ft³ to 180,000 ft³. Gasholders, such as the VSO Biogas Technologies’ gasholders installed by GTI, can be either pad mounted for solid structure digesters, or mounted directly on round digester tanks. By investing in a gasholder, you can operate your digesters with lower energy demand.

Waste-to-Energy Projects
Wastewater and organic wastes hold tremendous amounts of power, which explains why waste-to-energy initiatives are popping up at many industries, municipalities, and agricultural operations. Some examples of these alternative energy applications include:

Pinnacle Foods
As part of the wastewater treatment plant expansion, Pinnacle Foods introduced anaerobic digestion technology. By capturing the biogas generated from the anaerobic process, Pinnacle Foods can harness the energy to offset costs and become more sustainable. The system can generate 67,000 ft³/d of biogas, which is utilized in a new boiler at the treatment plant, helping to heat the digester to the proper temperature. The insulation provided by the cover also helps the digester retain heat more efficiently.

City of Tulare
Energy conservation is extremely important to both the City of Tulare and its wastewater treatment facility. The city wanted a means to reliably collect biogas from anaerobic digestion while also controlling odors and reducing greenhouse gas emissions. The solution was a 4 acre floating gas collection cover that collects up to 600,000 ft³ of biogas per day. This is enough biogas to generate a significant portion of the plant’s required power, making the facility less dependent on the area’s electricity grid and helping to offset energy costs.

LaForge Bioenvironmental
LaForge Bioenvironmental operates a waste-to-energy facility in a small farming community. It wanted to convert an existing concrete holding tank into a digester, and needed an accompanying cover to collect biogas from the anaerobic digestion of mixed wastes. The cover can operate under both positive and negative pressure. Under positive pressure, the cover inflates into a dome and stores biogas. Under negative pressure the cover rests on the liquid surface, which is the safest mode for retrieving samples or performing maintenance. LaForge now produces up to 1.5 MW of electricity and tied into the local power grid.

When tanks and lagoons are left uncovered, biogas – along with all the money-saving potential that comes along with it – disappears into thin air. Take advantage of the opportunity to convert waste into energy at your facility. In addition to attractive cost savings, by preventing methane from escaping into the atmosphere with a gastight cover, you will be helping save our planet.?For more information contact: Victor Cormier, President of ?Geomembrane Technologies Inc., covers@gticovers.com


City of Tulare
Energy conservation is extremely important to both the City of Tulare and its wastewater treatment facility. The city wanted a means to reliably collect biogas from anaerobic digestion while also controlling odors and reducing greenhouse gas emissions. The solution was a 4 acre floating gas collection cover that collects up to 600,000 ft³ of biogas per day. This is enough biogas to generate a significant portion of the plant’s required power, making the facility less dependent on the area’s electricity grid and helping to offset energy costs.

LaForge Bioenvironmental
LaForge Bioenvironmental operates a waste-to-energy facility in a small farming community. It wanted to convert an existing concrete holding tank into a digester, and needed an accompanying cover to collect biogas from the anaerobic digestion of mixed wastes. The cover can operate under both positive and negative pressure. Under positive pressure, the cover inflates into a dome and stores biogas. Under negative pressure the cover rests on the liquid surface, which is the safest mode for retrieving samples or performing maintenance. LaForge now produces up to 1.5 MW of electricity and tied into the local power grid.

When tanks and lagoons are left uncovered, biogas – along with all the money-saving potential that comes along with it – disappears into thin air. Take advantage of the opportunity to convert waste into energy at your facility. In addition to attractive cost savings, by preventing methane from escaping into the atmosphere with a gastight cover, you will be helping save our planet.?For more information contact: Victor Cormier, President of Geomembrane Technologies Inc., covers@gticovers.com http://www.gticovers.com

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