Keeping Landfill Gas-to-Energy Burning for You

Elizabeth Kubis, Charlie Forbes and Tom Kerr

The local landfill in the city of Brownwood, Texas, saved more than $40,000 last March on leachate disposal costs.

Farther north, the operators of Seneca Meadows Landfill, Waterloo, N.Y., are processing landfill gas (LFG) for public use at a consistent 25 percent savings. And in Orange County, Calif., the Frank R. Bowerman (FRB) Landfill is projected to cut the county's public transportation system carbon monoxide (NOx) emissions in half by 2000.

What do these projects have in common? They are all the result of cost-effective approaches and innovative technologies involving the beneficial use of LFG. In the past five years, landfill gas-to-energy (LFGTE) efforts have seen renewed growth, and the following successful projects are proving that LFGTE can provide economical solutions to the most vexing of landfill operators' problems.

Until last year, Tim Airheart, Brownwood's solid waste superintendent, was paying almost 50 cents per gallon to have his landfill's leachate transported nearly 100 miles away to the nearest wastewater treatment facility in Irving, Texas.

To complicate matters, Brownwood's high precipitation rate produced leachate generation at the rate of approximately 50,000 gallons per month at this 17 million cubic yard design capacity site.

Costs for leachate disposal were prohibitive because the 648-acre site is located in the "dead geographic center of the state, not close to anything," Airheart says. The solution: a leachate evaporation unit that could be operated using the site's LFG as a primary energy source, addressing the facility's LFG and leachate disposal issues.

After expedited permitting, the evaporator unit underwent rigorous emissions testing. The system has been functioning since November 1997, and Airheart is pleased with the results: The system processes approximately 500 gallons of leachate per hour, running it through processing equipment and through two burners, which deliver up to 5 million British thermal units of evaporative heat.

The evaporator minimizes logistics associated with leachate disposal and is literally maintenance-free, because it can be run with minimal supervision 24 hours a day. "It provides us with a lot of peace of mind," Airheart says.

Cleaning Up Seneca Meadows "I have found something that makes the project economics work for me, even without [Section 29] tax credits," says Innovative Energy Systems Inc.'s (Clarence, N.Y.) Peter Zeliff of the LFG cleanup/refrigeration technology in place at the Seneca Meadows Landfill.

Seneca's LFG processing facility, which is designed to clean up LFG and thus reduce maintenance costs associated with the energy project, has been in operation for more than two years.

Approximately 2,200 standard cubic feet per minute of LFG are treated in a two-stage refrigerant and liquid desiccant process prior to fueling an on-site 5.6 mega watt (MW) generation plant.

Zeliff found this method to be relatively inexpensive in terms of processing and maintenance costs. The refrigeration process is crucial because it reduces wear on Zeliff's seven Caterpillar 3516 engines by eliminating cylinder deposits. In fact, Zeliff reports that he has more than doubled the manufacturer's rated engine life.

Although the system's installation cost was approximately 20 percent more than a more traditional LFG treatment unit initially, the long-term cost savings from decreased engine maintenance resulted in a one-year payback for the project. As a testament to the successful project economics, Zeliff is currently breaking ground on another 5.6 MW expansion at the same facility.

LFG Cruisin' in California The Orange County (Calif.) Transportation Authority and Ecogas/GSF Corp. (GSF), Austin, Texas, are working on a project where LFG is being processed into liquified natural gas (LNG) for use as vehicle fuel in the county's public transportation system.

Initially used as a bus fuel, the LNG eventually will power the county's light rail system. LFG will be drawn to the processing plant from the Irvine-based FRB landfill, a 726-acre, 7,000 ton per day, Orange County-owned facility at a rate of approximately 3 million standard cubic feet per day.

Future project economics look bright because Orange County ultimately will have a fleet of more than 600 buses consuming the equivalent of approximately 30,000 gallons of fuel per day.

"Long-term, we expect the economics of using LFG to improve relative to gasoline or diesel," says GSF's Ray Kuroki. "Our belief is that the price of these conventional fuels will rise gradually, whereas the cost of LFG-derived motor fuel will stay more or less the same."

Because LNG engines typically have much cleaner emissions than conventionally fueled engines, virtually all LNG buses are low-emission vehicle (LEV) certified, and many are ultra LEV certified. As this LNG technology becomes more advanced, and thus easier to manufacture, the LNG buses are becoming more affordable.

Due to various regulatory incentives, grant money also can help cover costs. For example, according to Jerry Wiens of the California Energy Commission, California Assembly Bill (AB) 1368 may soon make more than $50 million available to fund projects that provide cost-effective "NOx reduction benefits."

Under this bill, NOx emission reductions from diesel vehicles, such as fleet trucks and buses, will be valued at $12,000 per ton. The bill also makes available an economic incentive for fueling infrastructure to provide assistance to prospective LFGTE project developers.

Is LFGTE Right For Your Site? In order to be a viable host for a LFGTE project, a sanitary landfill must meet the following requirements:

* the landfill must have enough waste in place in order to generate enough LFG to meet the demand of the project (at least one million tons in place is recommended for most projects);

* the landfill must be close to the end-user, whether it is an on-site project, an off-site, direct-use application or the electrical grid; and

* the cost of the recovered LFG as a usable fuel must be significantly lower than conventional fuels that are available (at least 25 percent lower in price is the typical goal).

If these factors are in place, then the appropriate project-specific equipment and technology can be tailored to meet the landfill's characteristics. Cost-effective approaches and innovative technologies can help to make these projects a reality.

The following solutions also have been used to bring real money savings to landfill owners:

* Lean-burn internal combustion engines can be used to optimize air-to-fuel ratios and improve fuel economy and reduce engine wear.

* "Landfill gas farming" uses leachate recirculation to maximize energy recovery through accelerated LFG generation. This approach also promotes landfill stabilization, thereby minimizing long-term post-closure maintenance costs.

Building cost-effective LFGTE projects in the current competitive marketplace can pose significant challenges to the potential project developer.

However, a combination of factors continue to spur on project developers to implement successful LFGTE projects; including:

* new, more cost-effective approaches that use long-established energy conversion technologies;

* innovative technologies that convert LFG to a marketable commodity more efficiently; and

* increasing requirements for LFG control.

Deregulation of the electric industry provides an additional opportunity for LFGTE to be seen in a fresh light.