Public or private, every landfill is a potential power resource, according to Prometheus Energy.

By Dan Rafter

Kirt Montague sees his company’s new landfill-gas (LFG) conversion facility in southern California as just another step in knocking down the hurdles preventing municipalities from turning plentiful LFG into a major source of fuel for fleets of trucks, busses, and emergency vehicles.

The conversion facility, now turning streams of LFG into liquefied natural gas (LNG) at the Frank R. Bowerman Landfill in Irvine, CA, is the first commercial plant of its kind. But if Montague, chief operating officer of Bellevue, WA–based Prometheus Energy, has his way, it won’t be the last.

The plant—a modular design built at Prometheus’ Washington headquarters and then shipped as components to the Bowerman landfill—is far from imposing. It covers a total footprint of about 100 feet by 100 feet. But it is powerful. The plant, which began operating at the Bowerman landfill early in 2007, can produce about 5,000 gallons of LNG a day. Montague says that this is only a start; Bowerman currently flares enough LFG to make about 40,000 gallons of LNG daily. The day when Prometheus Energy’s plant is expanded enough to reach that capacity will come, Montague says. It’s inevitable.

“This is a project with great potential. The whole industry of converting landfill gas to liquid natural gas has tremendous potential,” Montague says. “Liquid natural gas is so flexible. It’s a highly valued commodity. Think of the other options you have if you’re running a landfill today. You can clean up the gas and put it into a pipeline grid. Or you can use the landfill gas without cleaning it up to generate electricity. Your profit is dictated by what price you can get, or by whatever the value of electricity is. You can see the profit margin opportunities by making liquid natural gas as opposed to cleaning up landfill gas.”

The entire output of Prometheus’s new Bowerman plant—which will be built in three separate phases until reaching its maximum LNG potential—is being used as alternative fuel for the fleet of busses run by the Orange County Transit Authority. The authority had long been running its buses on LNG but had to purchase most of it from outside sources. The authority now uses all the liquid fuel produced by the LFG at Bowerman. For now, Bowerman does not produce enough LNG to satisfy the transit authority’s needs; The authority uses about 13,000 gallons of LNG a day, so it will continue purchasing the rest of the fuel it needs to power its fleet from other developers. But once the Bowerman landfill facility’s conversion plant has ramped up enough to produce more than 13,000 gallons of LNG a day, the transit authority will no longer need to purchase the fuel from outside sources.

This is a benefit not only to Orange County, which will save dollars on its fuel costs, but to the health of the county’s residents. At a production level of 5,000 gallons a day, the Bowerman project reduces carbon-dioxide output by the equivalent of 10 tons per year. When fully built out, and when the plant is producing its 40,000 gallons of LNG a year, the Bowerman project, if all the liquid fuel it produces is used, will have the same environmental impact as removing 150,000 cars from the road.

Montague says he expects more landfill operators, both public and private, to invest in plants that convert their facilities’ LFG into LNG for one reason: It makes economic sense. Examples such as the one taking place now at the Bowerman landfill will only speed up clients’ appreciation of LNG derived from LFG, he says.

“There are so many opportunities at both community-owned and privately held landfills to use the gas produced there,” Montague says. “Yes, the owners of these landfills are trying to do something economically viable with their gas streams instead of just flaring them. But many of the private landfill operators we’ve spoken to have their own garbage fleets that they operate. We can sell them liquid natural gas from their own facilities that is 30% less costly than the diesel they are currently using to power their vehicles. It’s also a clean-burning source of renewable fuel. Those are some good selling points for liquid natural gas.”

A Mission
The Bowerman landfill project is not the only LNG conversion project that Prometheus Energy is tackling.

The company is now working with the Polish company Cetus Energetyka Gazowa to form LNG Silesia. The company will transform methane gas from the vast number of coal mines in southern Poland into LNG to serve emerging alternative-energy markets in the country.

Prometheus is also now in the late design phase of an LFG-to-LNG project at the Kiefer Road Landfill in Sacramento County, CA. Its reach in California includes a third project, this one in San Joaquin County. Here, Prometheus is taking the gas from a stranded gas well and converting it, too, into LNG. In all, the company is working on developments with an estimated capacity of 65,000 gallons of LNG per day.

To Montague and the other five individuals who founded Prometheus in 2003, this flurry of activity offers proof of the sound economics behind their dreams of taking energy sources that would otherwise be wasted and transforming them into clean-burning renewable fuels.

Prometheus officials, though, realize that dreams alone can’t sustain their alternative-energy firm. But by extending their reach overseas with their project in Poland, Prometheus’ founders hope that they are increasing their still-young company’s chances for success. The reason? Overseas clients have different reasons for investing in converted landfill and other waste gases than do their counterparts in the United States. Prometheus, then, is diversifying its services.

In this country, Montague says, clients are interested in LNG because they are looking for cleaner-burning fuel sources and often must meet federal and state regulations calling for lower emission levels. Prometheus’ client in Poland, though, is interested in liquid natural gas strictly for economic reasons. The client can purchase LNG from Prometheus at a cost of 30% to 40% lower than what it would otherwise spend to buy diesel or propane.

John Barclay, one of Prometheus’ founders and its chief technology officer, says that a growing number of municipalities and private companies are recognizing the value of LNG derived from otherwise wasted LFGs.

There are two reasons for this, Barclay says. A number of municipalities across the country run an open-bid process for the private waste companies that are vying to handle their garbage collection and disposal.

For a growing number of municipalities, one of the requirements for private disposal firms hoping to receive their business is that their fleets include vehicles that use renewable fuels that reduce the amount of emissions they spew into the air. By including vehicles that use LNG in their fleets, waste companies satisfy this requirement.

Secondly, Prometheus can sell its LNG at a discount to what diesel currently costs companies and municipalities. Biodiesel, another alternative form of energy, is intriguing, but is also quite costly, far more so than is LNG.

“Liquid natural gas as a vehicle fuel is such a tremendous source of energy, such a wonderful solution for clients looking for an alternative to diesel,” Barclay says, “it makes very good economic sense for them. You don’t need government subsidies to make it work. It’s an economically viable solution. It’s one of the reasons why California is so interesting. They recognize that liquid natural gas is a great vehicle fuel for heavy-duty vehicles.”

There is no shortage of potential sources of LFG to be converted to LNG, either, Barclay says. The Environmental Protection Agency’s Landfill Methane Outreach Program maintains a large database of landfills across the country that would make for good sources of waste energy to be converted to LNG. The number of potential candidates for LNG production is in the thousands, Barclay says.

“A lot of people are becoming aware of these sources now,” Barclay says. “We do see competition from other alternative fuels. But those alternatives still suffer from marginal economics at best when compared to liquid natural gas.”

Despite recent advancements in the industry, there are still hurdles to overcome before LNG becomes a mainstream fuel, Montague says. One of the biggest is what Montague calls the credibility factor: Many municipalities and private companies are hesitant to place their trust in LNG. They’re not familiar with the product, and don’t necessarily believe that they can find a reliable source of it. They’re also not familiar with the companies that come to them with LNG proposals.

“Product credibility right now is probably the biggest challenge we are facing when it comes to liquid natural gas,” Montague said. “The landfill-gas business has long attracted a variety of different players with creative solutions on how to deal with waste and landfill gas. Most have not proved to be as good as characterized by those promoting them. For us, the biggest hurdle is the credibility. Fortunately, this is something we are putting to bed. We have already proved that we can create high-quality liquid natural gas. We can point to the projects we have ongoing. When we are producing 5,000 gallons of liquid natural gas a day, we don’t have that argument or hurdle to face anymore.”

Environmentalists have raised other questions about the production of LNG. They worry that the large-scale production of the fuel causes enough harm to the surrounding environment to negate the positives of generating an alternative energy source.

But, Montague says, these critics fail to differentiate between the large-scale and small-scale production of LNG. Prometheus at Bowerman, for example, is engaged in small-scale production. Its plant, remember, only covers a footprint of 100 feet by 100 feet. This is far different from a massive production plant.

Barclay and Montague both predict that companies such as theirs are steadily overcoming such hurdles. The key, they say, is to continuously educate private firms and municipalities about the benefits of converting waste gases into LNG.

“For fleets to change from a fuel that they’ve known and used for some time, like diesel or gasoline, to liquid natural gas involves a lot of changes on the operators’ part,” Barclay says. “If you are a fleet owner/operator, you’d say that you’d need at least three secure sources of liquid natural gas to make sure you’re never caught without enough fuel. We are now getting through that issue. More and more infrastructure for producing liquid natural gas is being put into place. That is going to change the perception. We are just on the cusp of that wave right now. We just have to get more of these projects done, get more of these fuel sources.”

The Right Engine for the Job
Prometheus’ Bowerman landfill plant, a landfill owned and operated by the Orange County Integrated Waste Management Department and located about 40 miles south of Los Angeles, relies on its own proprietary method for removing carbon dioxide through cryogenic separation.

Prometheus’ liquefying process relies on filters, phase separators, selective reactions, and freezing and cryogenic refrigeration techniques that purify and liquefy LFG streams to produce liquid natural gas that has a methane content of greater than 97%.

To produce LNG, the source feedstock—in this case, LFG—must be compressed, purified and cooled. To do this, Prometheus relies on a modular approach. An LFG system starts with a pre-purification module. This section of a Prometheus plant removes corrosive sulfur compounds, low concentrations of non-methane organic compounds, and water from the LFG stream. It also compresses the LFG.

The second module, what Prometheus calls its bulk-purification module, removes carbon dioxide from the LFG stream, further purifying it.

Prometheus uses its proprietary cryogenic freezing process to precool the methane and any nitrogen in the stream while, at the same time, freezing out the carbon dioxide.

The system’s combined liquefaction and post-purification modules liquefy the purified LFG stream and boost the concentration of methane in the LNG by dynamic flash evaporation of the nitrogen. This reduces the concentration of nitrogen to less than 3% in the resulting LNG.

The refrigeration module cools the process stream in a closed-loop system that uses a separate refrigerant. It then remains immune from process-stream variations. The cryogenic refrigerant allows Prometheus to employ maximum precooling of the LFG process stream in stages, which helps increase the thermodynamic efficiency of the overall purification and liquefaction. Prometheus shipped the modules from its facility in Washington to the Bowerman site, starting the process in early 2006 and finishing the installation by the end of that year. The Bowerman LFG-to-LNG conversion system began operations at the beginning of 2007.

Prometheus runs and monitors the system remotely from its headquarters, taking much of the burden for maintaining the plant from the landfill’s operators.

A GE Energy Jenbacher LFG engine is powering Prometheus’ system at Bowerman. The unit, GE’s JGC 320 GS-L.L system, uses process waste gas and LFG to support the plant’s operations. The electricity generated by the gas engine is used in the gas compression and liquefaction stages of the LNG production process.

Officials with GE Energy’s Jenbacher division say that the Bowerman project, with its obvious environmental benefits, was a perfect project for the company’s gas engines.

“We are proud to collaborate with Prometheus Energy on this landmark landfill initiative,” says Prady Iyyanki, chief executive officer of GE Energy’s Jenbacher gas engines division, in a written statement. “This project is designed to offer significant environmental and economic benefits to Orange County and the entire state.”

David Gall, a sales executive for GE’s Jenbacher division, says that the Jenbacher engine had several important features that made it the right engine for the Bowerman landfill project.

The biggest of these is the engine’s versatility, Gall says.

“One of the engine’s strong assets is its ability to operate on different fuels,” he says. “It is certainly an extremely versatile technology. That’s why it’s become so popular in landfill-gas projects. The engine has a lot of flexibility. It can adapt to so many different environments.”

The Jenbacher engine, in fact, is in demand not only for LFG applications, Gall says, but is highly regarded as a power source for several different kinds of waste-gas applications.

“This engine can be used for a wide variety of projects, for a wide variety of waste gases,” Gall says. “We waste so much gas by flaring it. Landfill gas is a big and growing market in the United States. The use of biogases has a big potential, too. A wide range of municipalities are looking into digester gases and other biodegradable fuel sources. A lot of municipalities are seeing the opportunity to take advantage of this gas that they are producing and just flaring away.”

Officials at Prometheus expect the Bowerman landfill to continue generating LNG for decades.

“Any time you are turning a landfill gas into liquid natural gas, you are creating a renewable project,” Montague says. “Landfills are effectively renewable. Even after a landfill like the Bowerman landfill is eventually closed, it takes 20 to 30 years to convert all those gases into fuel. You are taking a waste product and converting it back into fuel. It is a renewable energy source.”

Writer Dan Rafter is based in Chesterton, IN.

DE - November/December 2007