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Converting Biogas into CNG for Alternative Vehicle Fuels

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CNG fueling station in Riverview, MI
New technology is being developed in response to a growing interest in lower-cost vehicle fuel alternatives. One example is the patent-pending BioCNG biogas conditioning system invented by Cornerstone, which economically converts methane produced from the decomposition of organic waste materials—or “biogas”—into a renewable natural gas (RNG) suitable for use in compressed natural gas (CNG) vehicles.

The first BioCNG system was installed in December 2010 at the Rodefeld Landfill in Dane County, WI. After applying for a US patent in June 2010, Cornerstone began marketing BioCNG to the US marketplace. The company also established relationships with national equipment manufacturers to help deliver biogas equipment.

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CNG fueling station in Riverview, MI

Today, the system is used to convert biogas into compressed natural gas (CNG) fuel at 10 systems in eight locations in the US. In 2011 and 2012, BioCNG received the EPA Landfill Methane Outreach Program (LMOP) Project of the Year award for its technology. Some of the projects have received alternative fuel production tax credits or rebates through state programs and renewable fuel credits through the EPA’s Office of Transportation and Air Quality.

Lower-Cost Vehicle Fuel Alternative
At less than $2 per gallon of gasoline equivalent (GGE), biogas is a low-cost alternative clean vehicle fuel that is competitive with gasoline and natural gas. The system allows owners to fix their fuel costs for 10 to 20 years and helps meet aggressive national goals calling for reducing dependence on foreign oil by increasing the availability and use of domestic resources. It offers a renewable fuel alternative not dependent on foreign producers or fluctuating market prices.

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St. Landry Recycling Center

Developed using proven industrial gas conditioning technologies, the BioCNG system can economically address small-scale biogas producing facilities. The technology quickly demonstrated that even a 50-scfm biogas source can produce the equivalent of 250 gallons of gasoline each day, resulting in significantly higher revenue and environmental benefits that have been obtained from traditional biogas to energy projects.

Cornerstone conducted a rigorous gas composition analysis to demonstrate that the fuel produced by the system is acceptable for use in CNG engines. The evaluation determined that the system produces a fuel that meets or exceeds both the SAE J1616 Recommended Practice for Compressed Natural Gas Vehicle Fuel and heavy-duty natural gas engine manufacturer Cummins Westport’s fuel specifications.

Cleanworld’s Biodigester in Sacramento, CA

BioCNG in Action
The system is working well in California, Louisiana, and Colorado. Rather than just a standalone BioCNG biogas conditioning system, these are total vehicle fueling systems that integrate with the client’s facilities.

One example is the system developed for CleanWorld’s Sacramento BioDigester at the Sacramento South Area Transfer Station in Sacramento, CA. The project was awarded the 2013 International Bioenergy Project of the Year at the Renewable Energy World Power Engineering awards event. The facility is a public-private partnership between the County of Sacramento, which owns the site, and CleanWorld, which owns and operates the BioDigester facility. Local hauler, Atlas Disposal Industries, built and operates an adjacent CNG fueling station that fuels local fleets with renewable fuel created by the digester.

Another Cleanworld Biodigester

The system uses about 100 scfm of gas from the food waste digester, which yields up to 600 GGE per day in fuel. Cornerstone provided fabrication, materials, and start-up of a biogas conditioning skid for use with an existing CNG fueling station. Additional work included site equipment layout and piping design, integration with CleanWorld’s digester equipment, and integration with the CNG fueling station.

The original site layout, piping, condensate management, waste gas flaring, and controls were designed to accommodate an additional BioCNG unit, and expansion of the facility is now complete. It has the capacity to produce an additional 1,200 GGE per day of fuel.

As Michele Wong, CleanWorld’s CEO, notes, “The scalability of BioCNG’s skid-mounted units match well with CleanWorld’s modular approach and allowed the gas refining technology to be scaled up ­efficiently along with the digester as the system capacity was increased from 25 tons per day to 100 tons per day.”

“We were really excited to work on this project and thrilled that the City of Sacramento had the vision needed to make this project a reality,” says Mike Michels, Cornerstone’s executive vice president. “The city refers to the project as a ‘farm to fork to fuel’ project, which is a great way to express the growing understanding that our resources are precious and touch all aspects of society. We are especially proud that this is California’s first commercially available carbon-negative fuel.”

Another turnkey vehicle fuel system was developed at the St. Landry Parish Solid Waste Disposal District landfill in Louisiana. The project included engineering, permitting fabrication, materials, installation, and start-up for a biogas conditioning unit and an expansion unit, as well as provision of the gas cleanup skids, CNG fast fueling station, and CNG storage tanks, and facility construction.

The original system produced up to 210 diesel gallon equivalents (GGE) per day of biofuel vehicle fuel, at less than the cost of diesel. The fuel is produced from 50 scfm of biogas, containing 52 to 56% methane. The parish initially used the fuel to power 15 sheriff’s department vehicles and district support vehicles.

In 2015, the project was expanded to include an additional BioCNG system and a remote CNG fueling station supported by a CNG tube trailer that transports the biogas from the landfill to the remote station. A new unit tripled the fuel production to 630 GGE per day.

The expansion is part of a contract between St. Landry Solid Waste Disposal District and Progressive Waste Systems. In exchange for continuation of its existing waste hauling contract with the district, Progressive Waste agreed to purchase new CNG-powered trucks and fuel from the increased BioCNG generated from the expanded system. The completed project also will provide biofuel to additional St. Landry Parish clients.

District executive director Katry Martin was especially happy about the latest expansion, saying, “The fact that the hauler that delivers waste to the parish landfill will fuel its trucks with the biogas generated from the landfill is a true example of the power of renewable energy sources and a preview of the future of biogas.”

Another example of a recent system installation is at the Persigo Wastewater Treatment Plant (WWTP), which is jointly owned by the City of Grand Junction and Mesa County, CO. The BioCNG system will produce up to 500 GGE per day from the WWTP digester gas, which is piped about 6 miles to Grand Junction’s existing CNG fueling station. It will fuel a fleet of buses owned by Grand Valley Transit (GVT) and fueled at the City of Grand Junction facility, as well as city refuse trucks, street sweepers, and general utility pickup trucks. The City of Grand Junction and GVT continue to purchase additional CNG vehicles to increase the overall CNG fleet.

“We are extremely proud of this project, which has allowed us to utilize the biowaste at the wastewater plant to create fuel for our own fleet,” says Tim Moore, Grand Junction’s interim city manager. “It has really put us on the map in terms of alternative fuel use, and we are realizing a direct benefit from the resulting energy and cost savings.”

Michels concludes, “It is very encouraging for us to be able to contribute to sustainability through the generation of renewable fuels. The modular nature and flexibility of the technology make biogas perfect for so many practical vehicle fuel applications.” MSW_bug_web

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