While the badly needed federal price support for landfill gas-to-energy (LFGTE) projects continues to languish in Congress, smaller but viable LFG-recovery projects are being installed to meet the energy needs of landfills and nearby customers at a fraction of the retail prices charged by the utilities.

By Charles D. Bader

Sidebar An Alternative Scenario

According to the United States Environmental Protection Agency, there are more than 340 operational landfill gas recovery projects in the US. In addition, about 200 projects are currently under construction or are exploring development options and opportunities. These projects, as reported by the EPA Landfill Methane Outreach Program (LMOP), "are responsible for significant reductions in the emission of methane, a potent greenhouse gas. They also are preventing the emission of carbon dioxide, since using LFG for energy offsets the need to use other, more polluting fuels. In the year 2002, all operational LFG energy projects in the US prevented the release of 17.3 million metric tons of carbon equivalent (MMTCE, the basic unit of measure of greenhouse gases) into the atmosphere. This reduction is the carbon equivalent of removing the emissions from 13.9 million cars on the road for one year."

The LMOP report maintains that "LFG is a readily available, local, and renewable energy source that offsets the need for nonrenewable resources, such as coal and oil. In fact, LFG is the only renewable energy source that, when used, directly prevents atmospheric pollution. LFG can be converted and used in many ways: to generate electricity, heat, or steam; as an alternative vehicle fuel to fuel fleets like school buses, taxis, and mail trucks; or in niche applications like microturbines, fuel cells, and greenhouses. Of the 6,000 landfills across the United States, EPA estimates that as many as 500 additional landfills could cost-effectively have their methane turned into an energy resource, producing enough electricity to power 1 million homes across the United States."

For a nation concerned about both near- and long-term sources of energy, capitalizing on the energy potential of LFG would seem to be a no-brainer, even if we continue to ignore the need for a substantial reduction in greenhouse gas emissions is ignored. The IRS Section 29 credit for the sale of LFG-supplied energy expired in 1998, however, and bills to reinstate this or some other meaningful support for the development of alternative-energy sources in general and LFG sources in particular continues to languish in Congress. Without this support, the development of new LFG energy projects has slowed dramatically. In 2002, only 22 such projects went on-line.

The reason is obvious. Without the Section 29 support, LFG energy sold to the grid today brings only about 3 cents/kWh, according to Jeff Pierce, vice president of SCS Energy in Long Beach, CA. "Some municipally owned power companies may buy electricity from alternative-energy sources at perhaps 4 to 5 cents per kilowatt hour as part of their green power programs, but this revenue level just isn't enough to entice investors to lay out the capital costs for LFG-recovery systems for landfills with at least 1 million tons of waste in place, a threshold EPA believes that 'the best candidates' should exceed."

As a result, many developers are exploring development options and opportunities instead of proceeding with construction and installation while the congressional hiatus drags on. But at least one company is finding a viable approach to LFGTE development in small distributed-generation projects that increase net returns by reducing current retail power costs for their existing operations. The leader in this movement appears to be SCS Energy, which has a dozen such projects already in operation. The key, according to Pierce, is a selection strategy based on the existence of four basic conditions:

Not surprisingly, California landfills mostly meet these conditions, although viable opportunities do arise in other states willing to support alternative-energy development or air-pollution reduction. "California is the most progressive state in supporting the generation of power from alternative-energy sources," asserts Keith Field of Capstone Turbine Corporation in Chatsworth, CA. "On July 3, 2001, the California Public Utilities Commission initiated a program to offer customers of Pacific Gas and Electric, San Diego Gas & Electric, Southern California Edison, and Southern California Gas Company incentives to install 'self-generation' units to lessen the electricity load on the power grid.

"Under the Self-Generation Incentive Program, utility customers are encouraged to install submegawatt generation systems on their own property to supply all or a portion of their energy needs. To qualify for the program, the systems must be interconnected for parallel operation with the utility grid so they can supply excess power to the grid. No incentives are provided for diesel-powered or backup generation units.

"Incentive funding under this program will be available through 2004. For systems such as Capstone's microturbine-based systems using renewable fuels such as LFG, the Self-Generation Incentive Program can rebate 40% of the installed base up to $1,500 per kilowatt."

George Wiltsee of the Ingersoll-Rand Energy Company in Davidson, NC, adds, "That powerful an incentive, coupled with California's unusually high retail rate of 14 cents per kilowatt-hour, enables a landfill operator or a developer to make an LFG-to-energy project pay for itself pretty easily. It values the electricity it produces for its own needs at the utility's retail rate by offsetting the purchase of electricity from the utility. In effect, every kilowatt the LFG-to-energy system produces is worth the 14 cents per kilowatt-hour it would otherwise pay to the utility in California. And that rate is far more than the 3-cents-per-kilowatt-hour wholesale rate the utilities have been offering to alternative-energy companies to supply electricity to the grid."

Utilizing the Power

Diver ready to enter a 100-ft. leachate shaft to clean out debris

Since EPA calculates that the cost of generating power from LFG is between 4 and 7 cents/kWh, this would appear to be an ample margin for a project whose capital costs had been defrayed by 40%. It must be remembered, though, that this scenario assumes there is a need at the landfill site for all of this energy being developed, and most landfill operations don't have large power requirements. As Pierce points out, "A landfill might need electricity for flare-station operations and for leachate treatment operations, and it might have a co-located [material recovery facility] with power requirements for such things as grinders and separators. Those requirements typically aren't going to need much of an energy-generation capability. For example, our Butterfield Landfill project in Phoenix employs just one 70-kilowatt microturbine that is fired on landfill gas with a methane content of 40%. That small system generates power that far exceeds the landfill's energy requirement, so it is able to export plenty of excess power to the local power company, Arizona Public Service Company."

Of course, if there are satellite or customer facilities near enough to the landfill, it might be possible to "sell" some of the excess power to them at a discounted retail rate, rather than sell it to the utility at the low wholesale rate. "However," Pierce cautions, "any customer's property must be contiguous to the landfill for LFG-generated electricity to be sold to him directly. Of course, this legal limitation can be circumvented by piping treated gas from the compressor skid at the landfill to the customer's site. There, the gas can either be converted to electricity by an electrical generation turbine or used in a gaseous form for steam generation.

"A good example of how a two-site system would work is our Eastern Regional Landfill Project in [Lake] Tahoe, CA. The project employs two 70-kilowatt microturbines, one located at the landfill and the other located at a transfer station 1,000 feet distant. A skid-mounted 95-scfm blower/refrigeration unit pressurizes and purifies the raw landfill gas and routes the treated gas (1) directly to the microturbine at the landfill and (2) over a compressed gas transmission line to the remotely located microturbine at the transfer station. The system also contains switchgear and a step-up transformer at each site for separate interconnection to the local utility's facilities. Thus, the system will save the county money by significantly reducing electric power purchases at retail rates from the local utility during working hours and by generating additional revenues by selling electric power to the utility during nonworking hours. Had the transfer station been a commercial operation not owned by the county, additional revenues would have been generated by the sale of power to it."

Gas Collection
The existence of an existing LFG collection and flare system cuts the costs of a recovery-system project about in half, EPA estimates. Therefore, the economic viability of retail-deferred operations might well depend on the availability of such a system and the ability of the LFGTE system to tie into it. Pierce says that such a modular addition to existing collection facilities is rarely a problem. "Of course," he cautions, "there are cases where the methane content of the gas collected and sent to the flares is below what the gas-to-energy turbine can handle. In cases like that, we have simply tapped into a couple of wells that had a higher methane content and run a separate gas line from them to the power-generation system. On the whole, existing gas collection systems represent a reliable base for energy-recovery systems."

However, Wayne Brusade, president of Methane Divers in Port Huron, MI, doubts that every gas collection system is a reliable candidate to support an LFGTE system addition. "Our crews go down into landfills every day to do inspections and repairs to gas collection equipment," he says. "We've seen a number of instances where the trench hadn't been prepared properly, so settlement occurred and the lines sagged. And we are constantly repairing pumps, some of them hundreds of feet deep. What's more, we often see hose runs of 1,200 feet or more without any of the intermediate clean-outs that should be no more than 500 feet apart. We found one such hose run in California that was 3,000 feet long without any clean-outs. You can't maintain it."

Wiltsee hasn't encountered serious reliability or maintainability problems in many gas collection systems either. "Some require a more proactive preventive maintenance program than others, but our landfill gas-to-energy projects haven't been adversely affected by collection system problems."

Matching the Generation System to the Application
"Practically speaking," Pierce says, "distributed-generation systems can be a cost-effective solution up to a 1-megawatt size. To date, reciprocating engines have been by far the most common technology used to generate electricity from LFG, with 82% of all of the large installed projects using it. But now microturbines are becoming the technology of choice for the smaller power requirements of 500 kilowatts or less. Our largest distributed LFG-to-energy generation system in terms of microturbine capacity has been 420 kilowatts, provided by six Ingersoll-Rand 70-kilowatt microturbines. Our largest such system in terms of number of microturbines has had a generating capability of 300 kilowatts, provided by 10 Capstone 30-kilowatt microturbines. Where a generating capacity of 500 kilowatts to 1 megawatt is required, we have selected reciprocating engines as the technology."

Reciprocating Engines
Reciprocating engines used on LFG projects typically are four-stroke lean-burn engines that burn LFG with significant amounts of excess air to provide greater efficiency and lower NOx emissions. The engine is connected to a crankshaft that turns an electric generator to produce electricity. Reciprocal engines used at landfills range in size from 500 kW to 3 MW and are usually the most cost-effective electricity generators for landfills containing approximately 1 million–5 million tons of waste, which can typically support an 800-kW to 1-MW project. EPA estimates the cost of LFG electricity-generation projects to be about 4 cents/kWh plus an additional 3 cents/kWh if a new LFG collection system is needed or if other site-specific factors are involved. Reciprocating engines have lower unit-capital costs in their size range, have excellent reliability, and have lower fuel-processing requirements than turbines do. Reciprocating engines, however, have higher NOx emissions and higher maintenance costs than turbines do.

Microturbines

This 10-unit microturbine array at Calabasas (CA) Landfill was a successful 12-month, 97% availability operation.

Microturbines are relatively new to LFG operations but, as EPA LMOP's Brian Guzzone points out, "these small turbine/generator sets create new economic opportunities for landfills—especially smaller, younger, or closed landfills with relatively low LFG-generation rates. Although originally developed to run on natural gas, microturbines perform well on LFG. They can be used to provide both onsite power needs and power to electric grids, and they can be equipped with options that allow the user to recover waste heat for such purposes as heating water, greenhouses, or office space.

"Advantages of microturbines include their size [capacities range from just 25 to 250 kilowatts], modularity, and low-maintenance needs. A 30-kilowatt microturbine system is about the same size as a refrigerator and contains the turbine, generator, and electricity conditioning equipment in a single package. As a landfill develops, microturbines can be added to increase generating capacity and can be removed as generation decreases. Closed landfills can use microturbines to recover decreasing LFG flows to power onsite uses … and microturbines are also well suited to remote landfills where power and waste-heat demand is comparable to the turbine-unit output."

NOx emissions from microturbines are very low; in fact, both of its major manufacturers offer an NOx performance guarantee of 9 ppm (at 15% oxygen), almost 80% lower than is possible with a reciprocating engine. As a result, microturbines might be attractive to landfills facing stringent air-quality standards. Wiltsee notes that landfill project developers facing tight permitting constraints have shown a good deal of interest in microturbines. EPA estimates the capital costs of microturbine electricity-generation projects to be 7 cents/kWh, but programs such as California's Self-Generation Incentive Program make them cost-competitive with reciprocating engines for requirements up to 500 kW and cost-advantageous below that level.

There are two principal manufacturers of microturbines—Capstone Turbines and Ingersoll-Rand Energy Company. Currently, Capstone makes just a 30-kW system for LFG applications, but Field says the company intends to introduce a biogas-fueled version of its 60-kW module. Stressing the advantage of modular deployment and precise requirement-matching possible with the small units, Field describes projects that range from a single 30-kW system to an array of multiple 30-kW units as needed to meet each specific LFGTE system requirement. Although the system at Los Angeles's Lopez Canyon Landfill was designed principally as a pollution and gas-production demonstration system, its arrangement of 50 Capstone 30-kW units is an impressive example of the possibilities of a microturbine array.

Ingersoll-Rand has taken a different approach to microturbine size. Its basic unit is a 70-kW unit, and the company is about to introduce a 250-kW unit, both of which also can be linked into arrays. While less modular for intermediate requirements than Capstone's 30-kW-unit arrays, Ingersoll-Rand's larger units have a lower cost per kilowatt that will enable the company to cost-effectively compete for a wide range of LFGTE operations. However, even though an array of just three Ingersoll-Rand 250-kW microturbines would satisfy performance requirements of greater than 500 kW, Wiltsee says the company has no plans to address the market for LFGTE systems larger than 500 kW in competition with reciprocating engines.

"Distributed-generation systems of up to 500 kilowatts for retail deferral constitutes the natural LFG market for microturbines," Pierce agrees. "We use both Capstone and Ingersoll-Rand microturbines in our LFG-to-energy systems; the selection depends on each project's size and special requirements. We believe that right now the small distributed-generation project represents the best market for LFG-recovery systems with the industry conditions [being] what they are. Will conditions change? I simply don't know. I have been through so many promising energy bills that never [passed], I don't pay any attention to what's going on in Washington anymore. I'm busy enough with what we're doing."

Charles D. Bader is with Dateline II Communications in Los Angeles, CA.