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• At the Scrubbing Edge

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The clamor for energy that is clean and renewable marks a historic moment, and, for the distributed energy industry, quite an opportunity. Nothing epitomizes the new day better than the Energy Independence and Security Act of 2007 (EISA), which, with the stroke of a pen, has funded billions of dollars’ worth of energy retrofits, upgrades, and research initiatives for years to come. Although the law did not extend two longstanding funding streams of importance to onsite power (Renewable Electricity Production Credits and Clean Renewable Energy Bonds), look at what was enacted in their place. The following are highlights identified by EPA’s Combined Heat and Power (CHP) Partnership:

1. A Recoverable Waste Energy Inventory Program. (See EISA Section 452.) In this new provision, all major US industrial and commercial sites doing energy-generating combustion and having a project payback of five years or less will be kept track of on a national registry. This will facilitate scrutinizing opportunities for waste-heat recovery, development, and improvement. For each site, the US Department of Energy (DOE) will provide free advice and technical support. Better still, the agency will fund up to half the cost of any recoverable waste energy feasibility study.

2. A Waste Energy Recovery Incentive Grant Program. (See Section 451.) Projects recovering waste energy will get $10 per megawatt-hour gained during the first three productive years. Half of the incentive dollars will be funneled to utilities to enable purchase or transmission of this recovered power; other waste-heat recovery will earn $10 per additional 3,412 million Btus achieved, if the heat is applied to purposes other than those originally sought. (Not qualifying, though, are waste-heat projects already benefiting from specific federal tax incentives.)

3. An Energy Efficiency and Conservation Block Grant Program. (See Section 542.) This annual appropriation of $2 billion recurs each fiscal year, 2008–2012, to provide financial incentive for:

• Doing energy efficiency improvements
• Funding distribution-related technologies, including distributed energy and district heating and cooling systems
• Purchasing technologies to reduce, capture, and maximize use of methane and other greenhouse gasses (GHG) generated by landfills or similar sources
•  Developing onsite renewable solar, wind, fuel cells, and biomass
•  Doing any other activity deemed “worthy” by DOE, EPA, Department of Transportation, or Housing and Urban Development

Grants for investment in energy are to be apportioned at 68% to local governments, 28% to states, 2% to Indian tribes, and 2% by competitive solicitation.

4. Renewable Energy Construction Grants. (See Section 803.) Grants have been authorized to subsidize up to 50% of the cost of renewable energy electricity projects, including biomass and landfill gas production. (Further specifics as to amounts and terms are yet to be determined, but are already pre-authorized “as necessary.”)

5. Express Loans for Renewable Energy. (See Section 1201.) Small Business Administration funds are also being juiced to help businesses utilize biomass (including animal and other waste, but not unsegregated solid waste); again, specific amounts and total appropriations are not yet specified.

Lastly—but perhaps of more symbolic than tangible value, in capturing the mood:

6. “Regional Application Centers.” (See Section 375.) Established only a few years ago by DOE to facilitate CHP projects, are now being renamed “Clean Energy Application Centers.”

These centers don’t even include two other multi-billion-dollar EISA incentives to spur renewable fuel and biofuel production aimed at greener road travel. In all likelihood, fuel and engine improvement made here will carry over to stationary generators, too. Even the recent failure of the bipartisan 2008 Climate Security Act, which was aimed at curbing GHGs, is being downplayed as merely a temporary setback in the green-and-renewable revolution: After the new 111th Congress and president are sworn in, another perhaps even more aggressive bill is sure to be introduced.

In any case, around the globe, technology innovations and local initiatives are already far ahead of most politicians. A search of the Web for renewable and green distributed generation presents an impressive lineup of new products, emerging methods, promising pilot projects, and other interesting developments.

Photo: SmartSoil Energie

Modulators help to fine-tune flow rates and pressures.

Here, at any rate, are several undertakings all moving in that direction:

Animal Waste Biomass to Fuel the Nation
Yes, it poses biohazards and carries noxious odors; but if this biomass blossoms as an energy resource, as a professor of civil engineering at Texas Tech University is aspiring to achieve, then treated animal waste will become a prime mover of future renewable biofuel plantations. This would evolve into an infrastructure for distributed biofuel and power generation, on a scale of almost limitless potential.

The biofuel feedstock of choice is one you have probably never thought of: water hyacinth. As the system’s designer Clifford Fedler point out, this turns out to hold an exceptionally high energy-conversion value in gasification. All it needs in preparation is to dry in the sun.

Fedler, who is also a dean of the Graduate School, suggests that farmers willing to channel animal waste into this cash crop will find that it is easily converted to methane and then cogenerated power. The resulting electricity and heat could serve the farming operation itself; surplus gas could be sold to pipelines and power to the grid.

In fact, the combination of nutrient-rich animal waste and this particular energy-rich water hyacinth is so potent that, on a national basis, says Fedler, “If we were to recycle all the primary farm animal livestock waste produced in the US, it would yield about 4.9 billion tons of dried biomass.” This would be directly convertible into nearly 500,000 MW of electrical energy.

Photo: SmartSoil Energie

Tripling or quadrupling the gas yields of landfills is the aim of the SmartSoil horizontal well system recently introduced in Canada and Mexico.

A Portable, Onsite Biogas Refinery
Of course, animal waste is but one nitrogen source, and dried plants are just one feedstock. Another major onsite energy source, which is already the focus of much research and development, is human-generated trash.

In recent months, a group of engineers at Purdue University have developed a trash-processing mini fuel refinery, the size of a small moving van, capable of converting food scraps, paper, and plastic trash directly into fuel and electricity. Parallel energy conversion processes occur simultaneously. Designed initially for use by military field units, the system can easily be stationed just about anywhere that humans produce waste, but power and fuel are perhaps unavailable.

In order to prime the fuel-production process, some diesel oil is required to run the gasifier and the bioreactor until they begin producing fuel. The resulting waste-to-power output nets out to about 90% more energy gained than is consumed, reports Jerry Warner, founder of a project contractor firm, Defense Life Sciences LLC, which is collaborating with Purdue. Other participating firms include Bowen Engineering of Indianapolis, IN, Huston Electric of Lafayette, IN, and Community Power Corp. of Littleton, CO.

The energy station first separates food or other organic wastes, from paper, plastic, Styrofoam, and cardboard. The former goes into a yeast bioreactor to make ethanol (where wood chips can be added too); the other trash is gasified to make propane and methane. All three fuels then power an electric generator.

Initial field results of the operation have been better than expected, reports Warner.

Photo: SmartSoil Energie

LFG power plant fueled by horizontal pipe extraction system.

Nathan Mosier, another Purdue professor of agricultural and biological engineering and participant, points out that the digestion process is largely carbon-neutral. The only other byproduct of the process is non-hazardous ash waste.

Curbside or Neighborhood Trash-to-Energy Composters
Ethanol on a large scale is, of course, touted (with some controversy) as both clean and renewable. However, as the above example shows, smaller-scale production may also make a lot of sense. Critics of industrial-scale ethanol production, which is now heavily subsidized by the federal government, point to the adverse impact this is having on the cost of other foods and, even more so, on the undesirably high energy input and water requirements. Neither of these would be the case, though, if the national policy were to focus on localized, onsite waste-to-clean-power engineering.

This is indeed the premise behind a system being developed by a firm called CleanTech Biofuels Inc. of St. Louis, MO. CleanTech is capitalizing on the successful demonstration of new cellulose conversion methods that were developed recently at the Forest Products Lab at the University of California at Berkeley.

Photo: SmartSoil Energie

Professor Nathan Mosier of Purdue University inspects a jointly developed compact onsite biorefinery.

Photo: SmartSoil Energie

When the landfill is exhausted, the modulators can be lifted out and reused elsewhere.

The end-result: a process-engineered fuel.
Other appropriate cellulosic feedstocks include corn stover, wood waste, and switchgrass. In spring 2008, CleanTech engaged Hazen Research Inc. (Golden, CO) to build and run a municipal solid waste-to-ethanol reactor. The application employs a rotating pressure vessel that separates cellulosic material in curbside garbage to prepare it, yielding a raw material (i.e., recycled garbage). This of course costs less than farm produce and minimizes the need for water or land. CleanTech estimates that a fully developed system would reduce waste disposal at landfills by as much as 90%.

Methane Output Triples
Speaking of landfills, another emerging technology applies technologically equipped “smart” wells, arrayed in horizontal trenches, to enable collection of much higher volumes of landfill gas (LFG) than is possible with conventional designs. The developer is a Montreal-based firm, SmartSoil.

In this retrofit, a landfill’s existing vertical wells will typically be capped and replaced with new ones. These pre-fab, modular elements are equipped with sensors, logic devices, modulators, blowers, and software controls to fine-tune flow rates and pressures. As a result, a three- or fourfold increase in methane comes in an accelerated timeframe; instead of, say, 20 years for the extraction, gas can be fully tapped in just 10, and of course, the replenishment is ongoing.

Other benefits of this more engineered approach are many, as the company’s marketing manager Annie Boulanger points out. For example, “a young, small landfill can produce energy much sooner,” she says. Conversely, older or closed cells in aged landfills near exhaustion can sometimes be reopened and made profitable with new horizontal trenches. Landfills in climates that are tough for composting (i.e., dry deserts or cold northern latitudes) can be productive. The inefficiencies and drawbacks of vertical wells are eliminated. And when the landfill is exhausted, the modulators can be lifted out and reused elsewhere.

Economic payback “will, of course, depend on local energy costs,” she says, and projects may benefit from incentives in carbon and greenhouse credit markets. Intensified gas output will multiply the power generation available for sale.

Boulanger describes several case studies, which are supported by third-party evaluations:

• At the Lachute landfill in Quebec, where conventional wells would support only about 3 MW of annual generation, installing the horizontal system in 2006 began yielding enough gas—about 20 million cubic meters—to power six 1.6-MW Caterpillar engines, totaling 9.6 MW one year later. This system also eliminates about 350,000 tons per year of carbon dioxide. Its cost of 25 million Canadian dollars (CAD) is anticipated to pay back in less than five years.
• A very small LFG well at L’Ascension, Quebec, was evaluated, under an EPA rule of thumb, as capable of producing 0.8 MW of gas power over a 20-year period if tapped conventionally. As Boulanger notes, “0.8 is not very interesting. There is really no payback for 0.8 megawatts in Quebec.”

However, equipping L’Ascension with the SmartSoil modules will yield about 10.5 million cubic meters of gas, compressed into 10 years—enough to generate 5.4 MW from Jennbacher gensets, beginning mid-2009. And this comes despite cold and freezing much of the year. L’Ascension will cost about $12.5 million CAD, with payback due in five years.

• Down in the hot, arid latitudes of Ciudad Juarez in Chihuahua, Mexico, another landfill will soon yield 16 million cubic meters of gas for 16 years, translating into 6.4 MW. The $17-million CAD cost should bring a positive return-on-investment beginning in about five years.
• Also in Quebec, an unprecedented LFG application using only forestry pulp, paper, and woodchips was enabled by “smart” wells to yield 7 million cubic meters of methane yearly. This will fire wood kilns, eliminating costly butane deliveries. Payback on the $5-million CAD investment will come in just two years.

Boulanger says that no projects are yet on tap for the United States, but entry into this market seems inevitable. “We’re looking for first to be a great showcase,” she adds.

Overcoming Air- (and Gas-) Quality Hurdles
With these initiatives in progress, here may be an appropriate point to raise another crucial factor that will impact any onsite biogas revolution: namely, the considerable technical challenge of ensuring that new fuel is clean. Two entails separate issues: raw fuel quality, and post-combustion exhaust emissions.

LFG and digest biogas—unlike the pipeline variety—pose relatively greater challenges for effective, affordable removal of unwanted contaminants, such as moisture, nitrogen, carbon dioxide, sulfuric acid, and siloxanes. While pipeline-quality gas arrives at the combustion chamber relatively free of unwanted content, the kind from landfills or digesters brings a variety of elements, depending on the raw digestion source. Inline scrubbers are necessary, and the engineering of these, affordably and reliably, is an art unto itself. Just as challenging, too, at the backend, the need to eliminate primarily nitrogen oxide, sulfur oxide, and volatile organic compounds (VOC) from exhaust streams, is typically ratcheting ever higher.

As for this latter, the air-quality compliance issue is proving to be a major hurdle for decentralized renewable and green combustion-based power. Leslie Cook Wong, a Houston, TX-based permitting and project management consultant doing business as Spirit Environmental LLC, notes that landfills and other distributed biogas producers “have no choice where they’re located; because of the cost of transporting waste, they have to be near population centers to be accessible.”

She adds that tightened US ozone standards announced in March 2008 mean, too, that “most populated areas in the US are either already designated as nonattainment for ozone, or are at pretty high risk for going non-attainment,” as the restrictions take effect. Nonattainment means, of course, a region will be limited on the volume of nitrogen oxide and VOC that EPA will allow. This usually means it’s tougher to get permits for new stationary engines. It’s a serious challenge for the distributed generation industry.

As for landfill gas particularly, “a lot of it gets flared and wasted, because it is too expensive, too problematic, and too difficult to get a landfill gas-to-energy project permitted,” says Wong.

Air restrictions for landfills are eased a bit, because the gas will be emitted in any case, and better that it be usefully burned. However, the low-energy value of LFG, and high contamination, make energy projects somewhat difficult. With that in mind, the following innovation arrives with rather serendipitous timing.

Mercury Turbine and LFG: An Unexpected Match
Four years ago, when Solar Turbines introduced its lean pre-mix combustion system in the Mercury 50 line, the aim was to serve conventional markets with the highest-performing turbine ever. At the time, recalls sales engineer Mark Hughes, “We never thought of using them for landfills.”

But the Los Angeles County Sanitation District’s (LACSD’s) Ed Wheelis—who headed dozens of power plants laboring at the region’s many landfills—immediately recognized the implications of the proprietary combustion design for his LFG operations. Encountering Hughes at a trade show, Wheelis wanted to buy three turbines on the spot. He wound up actually getting the first three off the line.

Wheelis (now retired) appreciated that the combustion system would succeed in handling the exceptionally low-grade gas he was getting from LACSD’s Calabasas landfill near Agoura. In fact—as LACSD senior engineer David Czerniak pointed out in mid-2008—“This Mercury is the only technology available to us that can burn that quality of gas, and get us a permittable project… without backend emission control equipment, that’s actually become available, that will work, and is economically viable, so we’ll make money.”

Czerniak had worked for Wheelis and now develops, manages, designs, and builds LACSD power facilities. For years previous to this, the lack of a viable engine at Calabasas meant flaring gas wastefully or burning it for steam turbines; the latter, though, really didn’t pay.

“So, we’re pushing the envelope to see how low we can go, with burning this poor quality gas in a set of three turbines,” he says.

Each is rated at 4.6-MW gross; the actual net, though, will be just under 4 MW, as they operate initially at just 80% capacity. Even at this lower starting point, output will represent a 10-fold increase over any power plant the landfill has ever supported. The gas characterization as “poor quality” puts it aptly, but may be too generous: Calabasas struggles to give out just 30% methane by volume. This compares to about 50% that is typical at other landfills. (The balance consists mostly of useless carbon dioxide.)

Overcoming this feeble value is accomplished by applying a combination of technologies, including an unusual lean-mix combustion system, inlet cooling, and recuperated exhaust. Although developed for conventional power applications, especially where allowable nitrogen oxide emissions are extremely restricted, the mercury solves the major challenges at landfills, without even intending to.

First, as Solar’s head of combustion and power generation marketing Andy Lens recalls, to handle the unusually low-methane mix, a team of engineers spent a year developing and exhaustively testing new injectors.

Second problem: This turbine’s recuperator captures a typical turbine’s intense heat—which would otherwise be wasted and counterproductive at a landfill. Thus it boosts overall fuel-conversion efficiency to 38.5%, compared to about 31% in earlier-generation models.

A third issue, for any combustion, is control of emissions. Here, the partial pre-mix system eliminates the need for add-on SCRs entirely.

“CO emissions are pretty much wiped out, and [Solar] get very low NOx [nitrogen oxide] emissions out of it,” notes Czerniak.

So low, in fact, BACT standards (“best available control technology”) are likely to be lowered to less than 6 parts per million (ppm) nitrogen oxide, from the current 25 ppm, after measurements are completed.

Upon the plant’s commissioning in 2009, its output will power the county’s water treatment plants, enabling near self-sufficiency. Total estimated value, over the 20-plus-year life, should come to about $30 million, with payback in just four or five years, estimates Czerniak.

Greener and ever-renewable power: As the transition to it accelerates, the prospects bode well for developers who serve the demand, and thereby build for a sustainable future.