Some forms of alternative energy involve shifts away from traditional engines, motors and generators, while others are more focused on changing the fuel or power source involved.

The diverse subsectors within the energy-from-waste (EfW) industry include several different methods of providing an alternative to traditional power sources, but many of them still rely on conventional engines to tap into waste as an energy source.

Makers of engines and generators have tapped into their existing product lines to serve the growing energy-from-waste market and also have offered design modifications to provide customized products for waste-to-energy (WTE) producers.

Custom Designed
One of the world’s largest companies is among those putting time, energy and investment into designing power products custom-made for the WTE industry.

In a landfill- (LFG-) gas-to-energy project in Akron, Ohio, project engineering firm Hull & Associates selected the Waukesha APG1000 gas engine, also known as the “Enginator.” The Waukesha line is now made by GE, Stamford, Conn.

The APG1000 is one of GE’s leading entries in the EfW market, with the engine being displayed publicly for the first time at the Solid Waste Association of North America (SWANA) 2011 Wastecon event in Nashville, Tenn.

According to the GE website, www.genewscenter.com, the Waukesha APG1000 gas engine “can utilize a broader variety of biogases, including from landfills, wastewater treatment plants and agricultural waste.”

The company says its researchers conducted an 18-month redesign and testing process. Results of that process included “modifications to the combustion chamber; a new spark plug design; and a new fuel control system that simplifies engine startup and operation [such as] greater fuel tolerances allow it to handle fluctuations in the thermal quality of the biogas with little or no manual intervention.”

The modifications were designed in part, says an emissions testing services provider, to fit into the smaller EfW projects. “The upgraded Waukesha APG1000 biogas engine helps us address the demand for more biogas engine choices as more customers ask for more cost-effective on-site power solutions,” says Rafael Santana, president and CEO, gas engines, for GE Energy. “The engine is specifically of interest for smaller on-site power projects, notably in the 60 hertz segment for the United States.”

Steven E. Giles, alternative energy market leader for Dublin, Ohio-based Hull & Associates, says the APG1000 design efficiency brings with it the lowest emissions levels of any engine that Hull & Associates found suitable for the Akron project. (See sidebar, “A Case in Point”)

Other aspects of the GE Waukesha engine also have earned endorsements. “The APG1000’s new biogas fuel system has made a significant improvement to the engine’s load stability, despite fluctuations in the heating value of the fuel gas,” says Bob Weston, managing director of Entec Services Ltd., a New Zealand-based power systems supplier. “This is particularly beneficial on smaller digester and landfill sites, which, by their nature, are more prone to varying fuel quality. The new system provides an automated response to fuel gas fluctuations that results in faster, more reliable engine starts as well as more consistent engine output with less manual intervention.”

Keep it Green
One of the ways engine makers are appealing to WTE producers is by offering them a chance to further enhance their green credentials by using an engine with low emissions levels.

The MTU product line from Tognum AG, Friedrichshafen, Germany, bills its combined-heat-and-power (CHP) gas generator sets as “ecofriendly [with] low emissions, up to 50 percent less CO₂ (carbon dioxide) produced than conventional power plants.”

Caterpillar Inc., Peoria, Ill., also is producing gen sets and engines finding their way into EfW markets. In 2008, the company issued a white paper, “Sustainable Application of Reciprocating Gas Engines Operating on Alternative Fuels,” focusing in part on emissions levels.

The study’s opening remarks note that when engine technology is applied to reducing releases of methane (at landfills, sewage treatment plants and large agricultural and food processing sites), then the capture of those emissions is inherently good for the atmosphere.

Later in the white paper, authors John C.Y. Lee and Thomas Teo of Caterpillar (China) Investment Co. Ltd. and Peter Lau of Caterpillar Asia Pacific Ltd., look at improvements in engine emissions control systems.

The authors write that for the LFG-to-energy market, the Caterpillar engine division has been creating “engine designs that deal with fuel contaminants [that] have a 20-year track record of effectiveness. Engine designs have improved steadily and are available on even the most technologically advanced, high-efficiency gas engines on the market. Protections against impure fuel include:

• Gas-to-air coolers that lower the temperature of the gas after it is compressed, reducing moisture and preventing condensation and attendant acid formation later in the fuel delivery system or inside the engines.
• Gas-to-gas heat exchangers, typically made of stainless steel, that precool the gas entering the drier to reduce drier power demand. Gas leaving the drier is reheated later in the process by the gas-to-gas heat exchanger to prevent water from condensing downstream.
• Gas driers that reduce halogens and hydrogen sulfide (H₂S) in the gas. The device is usually a gas-to-liquid heat exchanger that uses a refrigerant. The gas is dried by chilling to a dew point of 36 to 37 F (2 to 3 C). Because halogens and H₂S (hydrogen sulfide) are water soluble, reducing water content also reduces their concentrations. The drier also reduces, to a lesser extent, some gas-borne siloxanes.
• Coalescing filters that remove any remaining water or oil droplets and remaining solid matter as small as 0.4 microns.
• Condensate drains that collect water removed from the gas. The water may be treated for discharge to a sewer system or reintroduced to the landfill to stimulate methane production.”

The authors say Caterpillar has similarly been researching how to tailor its engines for optimal performance in anaerobic digestion biogas applications. “Specific engine modifications include optimized jacket-water temperature, crankcase ventilation and use of corrosion-resistant materials,” according to the report. “As further protection against naturally forming acids, biogas-specific engine designs minimize the use of bright metals in components likely to come in contact with fuel contaminants or exhaust gases.”

In All Climates
Another engine maker competing in the segment is a second GE subsidiary, GE Jenbacher GmbH & Co., Jenbach, Austria. A recent Jenbacher installation in the LFG-to-energy sector was undertaken for the U.S. Armed Forces in Alaska.

In late July 2012, Doyon Utilities LLC, Fairbanks, Alaska, held a ribbon-cutting ceremony to celebrate the opening of what GE Jenbacher says was the first LFG-to-energy project in Alaska. GE’s Jenbacher gas engines, touted as “ecomagination-qualified,” are powering the plant, which is located on the Elmendorf-Richardson joint U.S. Army and Air Force base in Anchorage.

“Beginning in 2013, federal agencies will be required to use renewable energy sources to provide at least 7.5 percent of total electric consumption,” says Dan Gavora, CEO of Doyon Utilities LLC. “GE’s technology allows us to turn LFG (methane) into an energy source for the U.S. military base and also into a revenue stream for the municipal utility, which currently flares the gas instead of selling it. In addition, the plant will help the military improve its energy security and move closer to its renewable energy target.”

Doyon will own and operate the facility and will buy the gas produced at the municipally owned Anchorage Regional Landfill for at least the next 20 years, with an option for an extension to 40 years.

“This project with Doyon Utilities is another example of how GE’s Jenbacher gas engines are supporting distributed power projects around the world,” says Roger George, regional sales leader, gas engines, North America. “Our Jenbacher gas engines provide the fuel flexibility needed to accommodate the use of alternative fuels such as landfill gas while offering high levels of electrical efficiency.”

GE says its fuel-flexible Jenbacher gas engines are part of the company’s ecomagination portfolio. To qualify for the ecomagination portfolio, products and services must demonstrate both improved economic value and environmental performance. “Overall, GE’s gas engines business has more than 1,650 units operating on LFG with an electrical output of over 1,650 megawatts,” GE claims.

The term “greenhouse gas” (GHG) most often contains negative connotations associated with changes in the Earth’s atmosphere. However, another recent Jenbacher installation has taken literal GHGs—from a 125-acre tomato greenhouse—and converted them into power and fertilizer.

Houweling’s Tomatoes, Camarillo, Calif., is the site of what GE calls “the first combined heat and power greenhouse project in America that captures carbon dioxide for use in plant fertilization.”

Two GE 4.36-megawatt ecomagination-qualified Jenbacher J624 turbocharged natural gas engines help power a GE-designed CO₂ fertilization system. The plant has been designed to provide heat, power and CO₂ to Houweling’s Tomatoes’ greenhouse. The project represented the launch of GE’s J624 two-staged turbocharged gas engines for the 60-hertz market segment and was the first of these engines sold in the United States.

Alleviating this one greenhouse’s emissions problems is a long way from controlling the planet’s overall GHG emissions levels. It is one more sign, however, that entrepreneurs and multinational manufacturers are working together to harness waste and emissions to convert them to productive fuels, power or other products.

The author is editorial director of Renewable Energy from Waste and can be contacted at [email protected].