Creating 1 MW of power, reducing tons of air emissions, and saving hundreds of thousands of dollars is the crux of the Hill Air Force Base (AFB) Generation Plant project now underway just outside of Salt Lake City, UT, in Layton. Hill is located less than 1 mi. from the Davis County Landfill, a small to midsize landfill owned by Wasatch Energy Systems. Wasatch installed a gas collection system in the landfill a few years ago to control gas migration and decrease gas odor into the surrounding residential areas. The landfill has been flaring all of the biogas (400-600 scfm) into the atmosphere.

The landfill gas is a product of decomposition of the waste in the landfill. During the decomposition process, a biogas is generated that is made up of about 50% methane, 50% carbon dioxide, and trace amounts of nonmethane organic compounds. With the passage of the Resource Conservation and Recovery Act in 1976, landfills began monitoring, collecting, and disposing of methane gas produced by decaying waste, and more landfills and energy users are looking to use this gas as a renewable energy source.

When the new plant is complete, the landfill will divert the gas from the flare station, remove the moisture and other particulates in the gas, and, using a compressor, deliver the gas to the fence line of Hill AFB.

The biogas pipeline will extend from the fence line to the location of the new generation plant. The plant consists of a gas cleanup system, a gas metering system, and two gas engine generators. The gas cleanup system is a series of filters and will be used to remove fine particulates and any moisture droplets carried over from the landfill.

Pushing Forward

Pushing the Hill project forward are two other entities besides the Air Force - Wasatch and Exelon Services Federal Group. Exelon Services Federal Group is a division of Chicago, IL - based Exelon Services and focuses on energy projects. The firm works mostly with federal facilities, primarily with the Department of Defense, providing engineering and construction services. Exelon has done this type of project before for a private company in Sairless Hills, PA, however, involving two large landfills and piped gas. That project, operational for 10 years, provides energy to a U.S. Steel mill.

According to Nicole Bulgarino, senior process engineer in the Federal Group Engineering Department at the Knoxville, TN - based Exelon Services Federal Group, the plant's construction is part of a continuous and aggressive energy conservation program.

Hill AFB is utilizing a unique Super Energy Savings Performance Contract (ESPC): the Biomass and Alternate Methane Fuel Contract. The ESPC is a program of the Department of Energy (DOE) and will be used to develop and implement the project.

"The ESPC allows federal facilities to implement projects without having any capital investment," Bulgarino says. "The project is funded by third-party financing that we set up. The energy savings associated with these projects pays for the project, and Hill will make payments on the project, sort of like a mortgage payment, every year."

Although the financing - said to be in the millions of dollars - has been approved, Exelon still is searching for a bank with the best rate. Exelon's project in Pennsylvania did not include an ESPC. ESPCs, Bulgarino notes, were not available until 2002.

Another reason this project is moving forward is this: Federal facilities are mandated, by a presidential executive order, to reduce their energy consumption and increase their renewable energy sources. ESPCs allow them to utilize renewable energy. The presidential order requires that all federal facilities, by 2005, reduce their energy consumption by 30%.

Landfill gas has been collected and used as a fuel to generate power for more than 30 years in the United States. Still, the scale of this project makes it unique and a model for landfills of this size nationwide.

According to Nathan Rich, executive director of Wasatch, the design capacity of the Davis County Landfill is about 7 million tons of waste. Davis currently has landfill gas collection systems in about 2.5 million tons. "There's another 800,000 tons there that I don't have collection in yet, but it's going to take us another 20 years to fill the landfill," Rich says. "As the generation capacity of the older landfill starts to dwindle, we should be able to bring newer areas of the landfill on-line, maintain the same gas flow, and perhaps even increase it over the next few years."

The Davis County Landfill began accepting waste in 1952, but at that time it was a relatively small operation. When a special services district was formed in 1984, additional communities started using the landfill. Most of the waste has been placed since the 1984 time frame. In 1998, the old unlined landfill was closed and Wasatch opened a Subtitle D lined cell.

"This type of project isn't brand new, but there has been a move toward more smaller-scale projects like Hill to come on-line," Bulgarino says. "Traditionally, projects in the past have been larger-scale. Now people are more aware that you can use landfill gas on a smaller scale. Some landfills are smaller, and there isn't always an end user nearby."

How the Project Started, Support

In this case, the end user, Hill, is less than 1 mi. away. Bulgarino says Hill went to DOE and inquired about ESPCs, and the process began. Exelon has had a lot of support from Hill and the surrounding community.

"I've never seen an Air Force base move this fast on a project," Rich says. "Because we have a relationship with Hill on our steam sales, we're talking with their energy office on a regular basis. They were in my office nine months ago, and I was telling their Energy Manager Kent Nomura to take a look at doing something with the landfill gas."

Nomura happened to be at a conference, and he ran into some people from DOE who got talking with him about a program that could provide the financing for such a project, ESPCs. From that point, Nomura was the driving force behind the project. "I planted the seed, and once Nomura found a mechanism he felt could work for them, he's really been proactive in pushing this with the Air Force and some of the regulating communities," Rich says. "He's helped us identify funding to keep our capital costs down, and he found federal funding through the Utah Energy Office that's going to pay for some of our engineering costs."

Moving forward, Hill interviewed contractors, and five were given authorization to do these types of projects. Out of those five, Exelon was selected as the winner to design, construct, and complete the Hill project. The other four contractors were DTE Biomass, Constellation Energy, ESG, and Tri-Gen.

Why Davis Got Involved

Why did the Davis County Landfill get involved in the Hill project? According to Rich, the main reason is that the project benefits the district. A special service district, Wasatch operates the landfill and a waste-to-energy facility, Davis County Energy Recovery, a 410-tpd municipal-waste incinerator.

"Being a special services district, we are owned by Morgan County, Davis County, and 14 cities within those counties that we serve," Rich explains. "Hill Air Force Base is the largest employer in the state of Utah, so we have several relationships with them. First, they're a customer of ours. Our waste-to-energy facility generates steam, which we sell to Hill."

Rich says this new project is part of Wasatch's ongoing energy partnership with Hill, keeping it as a customer. The district also is working with Hill because its board of directors comprises the politicians, elected mayors, and city councilmen of these member cities, and they're very interested in the health and welfare of Hill AFB.

"What we're trying to do as a special service district is implement sound solid-waste management practices, and this is another part of the integrated solid-waste management that we provide to Davis and Morgan Counties," Rich adds.

Options Considered, Factors Guiding the Decision

Bulgarino says there weren't any other alternatives considered. "They had heard of landfill gas projects, and they are a base that's very aggressive in their energy program. They knew the landfill was right next door, so it was just inquiring about that and inquiring about the contract. We looked at using the gas in their boilers and other uses for the gas. We didn't go that route because the economics worked out best for them to generate power. They have a very large electrical demand."

Economics guided Hill's decision but not Wasatch's. "This fit their needs more," Bulgarino notes. "They don't have a very large significant year-round steam load, so the best use for the gas was to generate power. The power goes into their general distribution system."

Utah Power, Hill's utility provider, offers a special tariff for self-generating sources that use renewable energy or cogeneration techniques; the landfill gas project qualifies. Hill will enter into a contract with Utah Power to sell the power back to it. The contract is under rate schedule 37, which is about an average of $0.04/kWh.

Selling back 1 MW of power during 90% of the year at the $0.04/kWh rate, Hill will receive a credit on its utility bill of about $300,000-$400,000. "The credit Hill gets back from Utah Power enables them to make their payments for the next 20 years on this system to pay it off," Bulgarino says. "One of their main drivers for doing the project was to have a renewable energy source because this is very important to the reports that they do as a base."

Project Details, Progress

The project is not yet operational but should be by August or September 2004. The first steps for Exelon were doing a feasibility study, working with the landfill to enter into a gas agreement, and then submitting paperwork for air permits. "There weren't any pitfalls, but it was a task that we worked quickly to get done," Bulgarino says. "The air permit got approved at the end of the Christmas [2003] holidays. They're timely, and it wasn't too difficult because we were able to stay around the major modification threshold."

Hill is operating under a Title V Air Permit, which states that any new air emissions sources are required to get a construction permit. The engines involved are small, so the total emissions from them are under the federal major-modifications thresholds, which simply means that the State of Utah can issue the air permit.

After obtaining the air permits, Exelon did an electrical-distribution study and selected the types of engines that it now is using. "We used our past experience to decide on the lean Caterpillar engines," Bulgarino says. "Caterpillar is a well-known name, and their engines fit. They are a good match for the gas supply."

The two engine generators are Cat 3512 low-Btu-configured engine generator sets. Each generator has a nameplate capacity of 600 kW. The engines will operate at 500 kW, however, in order to take advantage of a renewable energy rate offered by Utah Power.

Prior to having Exelon manage the new system, the landfill was flaring the gas, and Utah Power was providing that 1 MW of power to Hill primarily through coal-fired units.

Economic Benefits

Rich says the project is not a big moneymaker for the district. The reason Wasatch is involved in the project is it wants to do the right thing with the landfill gas and support Hill at the same time.

"There's a fair amount of investment from the district to put this project on-line," Rich notes. "We're responsible for putting the landfill gas compression and conditioning station on-line as well as about 3,000 feet of pipeline. We have to compress the gas and clean it up and then push it to the base. Exelon and Hill pick the project up at the fence line. We have about a half-million-dollar capital investment in the project. I'm estimating our annual revenue at about $40,000 from this project."

Rich says the compressor is a two-stage positive-displacement blower; basically it's a bigger compressor. "It's got a refrigerator unit on it that cools the gas to at least 38°Fahrenheit. By cooling the gas, you drop the moisture out of it. Then we compress the gas and deliver that in an 8-inch HTPE pipeline that runs at about 20 pounds per square inch. We're sizing the unit to handle 900 cfm/scfm, but originally they will be accepting, depending on the quality of the gas, 400 to 500 cfm. We're oversizing the system a bit so we can give them some additional gas when it becomes available."

Rich says his main motivation for the project is not financial, and he's looking at a 15-year payback period on the project. "We got it to a point where I felt we're reasonably assured that the project will pay for itself at some point. So we have the finances to the point where it's going to pay to put the system in. Our main motivation is destroying landfill gas and putting it to a beneficial use."

Size Matters

In terms of greenhouse gas emissions, collecting and treating the gas is huge. Wasatch has been burning the gas in a controlled burn, which has products of combustion coming off of the flare. Now the new project will generate electricity.

Problems? Rich says the system on his side should be fairly straightforward. Wasatch is shooting for a relatively high availability of the system: 95% availability.

"What's going to impact us for system availability is simply power interruptions," Rich explains. "We've had occasional interruptions of the power provided by our local provider. There are no backup systems for power interruptions. If we had Utah Power interrupt power, it would bring the system off-line As we have additional landfill gas, one thing we will look at is 'Do we ship the gas, or do we put a microturbine there and use the gas locally to provide better availability?' We have a blower and a refrigerator. On the Hill side, it's substantially more complicated in that they're running internal-combustion engines. They can handle that because they have a good preventative-maintenance program."

Preventative Maintenance

The biggest issue is that moisture can accumulate in low points in the transmission pipeline and plug the pipe. If the moisture fills up the pipe, air can't be blown through it. Monitoring will stop this.

"We need to make sure that the gas is being adequately dried so that we can put it into the pipeline and ship it," Rich says. "There are filters and we're guaranteeing in our condensate knockout that we'll remove 99% of 5-micron particles. We don't want to feed anything into that engine because it'll shorten the life of the engine."

This is Rich's first landfill gas system, and he says Wasatch and Exelon are shooting for an August 2004 online date. So far, so good. At the time of this writing, Wasatch had a board meeting scheduled in February 2004, when it hoped to ratify a contract for the equipment procurement so six weeks later the equipment would arrive.

"We hope to be laying pipe in April and May and meet the project timeline with a month of cushion," Rich says. "Right now we're gearing up to put 1 megawatt of power on-line. Exelon's system right now consists of two engines, and I believe they're leaving space to drop a third engine on-line as we're able to develop additional landfill gas. Hopefully the Hill project will be a 1.5-megawatt project in a few years. I would recommend a project like this for other landfills nationwide."

With the upcoming energy bill, Rich is hoping for additional financial help. "Perhaps we'll get some tax credits to make things a little bit easier. This is something that bounces in and out of the bill. For these types of projects, to get them up and running, a tax credit for energy sales to boost renewable energy portfolios would certainly help. Every little bit helps. The big struggle in this state is generating power and then selling it. Because it's a regulated state, the only place we can sell it is to the regulated utility. We don't get a lot of additional money because it's renewable energy."

Basically, Bulgarino stresses, if Hill didn't have the project, it wouldn't be getting $300,000 to $400,000 credits every year. "Certain economic numbers are proprietary," she says. "In a sense, they're still buying the same amount of energy that they were before, but they're getting this credit because of the self-generation on-site."

Services, Equipment, and Facilities Involved in the Project

There are two generators, a building for personnel to sit in, typical switch gears to connect to the existing electrical distribution system, and the landfill gas pipe that is routed from the east side over to where the generators are going to be located. Exelon's experience is the reason it will handle the equipment and facilities.

"They selected us for our experience working with federal facilities on generation projects," Bulgarino says. "We haven't selected a building manufacturer yet. There is some other equipment involved, a compressor and dryer, but that's on the landfill site. The landfill brings the gas to the fence line, and then we bring it to the generator site, which is close to 9,000 feet of pipe."

Filters Help With Moisture, Corrosion Worries

Bulgarino says the filters are a package put on the engines specially for landfill gas. Landfill gas can contain contaminants, including such fine particulates as siloxane, hydrogen sulfide, and any moisture carryover. "These are the main ones that you worry about," she says. "It's important to filter out moisture because you worry about it causing corrosion to the engines and that moisture may contain hydrogen sulfide, and this can cause corrosion in the pipes. Corrosion would reduce the lifetime of the system."

With a continuing monitoring probe, the metering system draws a sample, which can detect fine particulates and moisture. The system is controlled automatically and is fed into the combustion control of the engines. "The air-fuel ratio is controlled based on this," Bulgarino says. "The system will be remotely monitored either by us or a subcontractor in Utah. They'll be on-site at least once a week just to check the engines and to do any necessary maintenance on it."

In the remote location, computerized reports can be generated for power output, fuel input, or fuel composition, and if there are any problems, Exelon personnel will be there quickly.

The gas metering system will continuously monitor the gas flow rate, the methane content, the oxygen content, and the carbon dioxide content of the gas. Both engines are lean-burn engines and use the fuel metering system to control air emissions by adjusting the fuel-to-air ratio. Lean combustion decreases the amount of nitrous oxide and carbon dioxide formed since the engine is operating at a higher air-to-fuel ratio. The excess air decreases combustion temperature, therefore decreasing the formation of thermal nitrous oxides. By using the Caterpillar lean-combustion engines, the annual potential emissions were under the federal major-modification thresholds, resulting in only a minor modification to the base air permit.

By displacing the utility-supplied electricity and diverting the landfill gas from the flare station, the net emissions will result in a reduction of 5,000 tons of carbon dioxide emissions, 5.5 tons of nitrogen oxides, 4.8 tons of carbon monoxide, and 19 tons of sulfur dioxide. Generating 1 MW of power with landfill gas is equivalent to taking 8,800 cars off the road, to saving 12,000 ac. of trees, to offsetting 200 railcars of coal, to saving 93,000 barrels of oil, and to powering 660 homes.

Lessons Learned

What has Exelon learned here at Hill in terms of challenges, responses, deviations from the baseline, superiorities, and shortfalls? According to Bulgarino, there were no deviations; the same plan was followed all along. "Lessons learned were mostly the timeline, trying to get the permits, to start as soon as you can," she says. "We were very fortunate to get the permit so quickly. They had a lot of community support from the county. They were supportive by helping agree for the landfill to supply the gas, and then the EPA office there was very supportive because it was a renewable energy project."

The timeline for permit applications is usually from four to nine months. Exelon's took about three months. "We not only crossed all of our t's and dotted all of our i's, but we had some people from the base who were very supportive. They pushed to get it done and talked to the right people about it. You have to educate people in the community as well as the environmental-quality office, whoever you're working with. If we had to give a presentation to the community, we would do that, but in this case we didn't have to because they were well-informed."

As of now, there have been no major challenges. "We're not there yet, and we may have something come up during construction," Bulgarino says. "I don't expect that. We plan to be operational August or September 2004. We're still designing, and the equipment is being ordered right now for the generation plant. Our experience and our presentation showed our superiority. There were no shortfalls."

The overall impact to the environment is a reduction that other landfills should take note of. "There are a lot of landfills still flaring the gas into the atmosphere," Bulgarino adds. "We're looking at some in California and Virginia."

Hill Air Force Base personnel asked that Bulgarino speak about the project on their behalf.

Pennsylvania, PA–based ROBERT GLUCK is an award-winning writer whose work has appeared in The New York Times and on Microsoft's multimedia encyclopedia Encarta.

DE - May/June 2004