The plant would operate as a separate business, and the city would only need to approve a lease and power purchase agreement

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AZTEC – The city of Aztec is considering a new method of energy-production, and a somewhat unconventional method, at that. It involves garbage.

"We're trying to rely more on our own energy so we don't have to purchase as much power from the grid," said Josh Ray, Aztec's city manager. "One alternative energy source that seems to work well in this area is solar."

Last summer, Aztec installed a one-megawatt solar farm in the west part of town. The power supplied by the solar farm, said Ray, in addition to one-megawatt of energy supplied by hydroelectricity, has made the city less dependent on grid power.

The forward-thinking city hasn't stopped with water and sun, however.

Several years ago, Ray contacted the Albuquerque-based company Yearout Energy Services, which has a subsidiary called YESCO that creates waste-to-energy units that take city refuse and turn it into electricity.

YESCO sent a team to Aztec to present the waste-to-energy plan to city leaders. Reaction to the project has been positive, said Ray.

"All of the commission members like it, and the mayor is very positive about it," he said, adding that the city's current power supplier, Guzman Energy, has also given its blessing for the plan.

Aztec Mayor Sally Burbridge said she's excited about the waste-to-energy project, and what it could mean for Aztec.

"It's a great opportunity to not only provide an additional source of power for Aztec, but to also address the global problem of our landfills filling up," she said. "It's a small step in the big picture, but a big step for our community."

Colby Greer, the general manager for YESCO, explains how the process works.

"The technology has been operating in the UK since 2001 in several locations, and has proven to be the cleanest 'non-incineration' method to destroy all types of waste to generate renewable power," he said. "We have several sites throughout North America and Europe in development currently."

Greer said the system utilizes a chemical reaction called pyrolysis, which is the endothermic gasification of waste in the absence of oxygen.

"Endothermic is a chemical reaction that absorbs heat in the absence of oxygen using an external energy source," he said. "Gasification is a thermal reaction of high carbon material in the presence of controlled steam and oxygen at high temperatures without combustion to produce a synthetic gas. Inside the system, the endothermic chemical reaction takes place inside a sealed chamber which has been designed, built and tested to achieve and maintain the negative oxygen/high temperature environment required to achieve the enthothermic reaction."

Within the sealed chamber, Greer added, the waste absorbs the external energy and decomposes (or roasts) the waste to produce a high carbon material and a gas called pyrogas. "Gasification occurs as the carbon char and pyrogas is mixed with a controlled amount of steam under extreme temperatures to produce (what's called) a syngas. The syngas is later combusted safely in another separate chamber, away from the carbon char, with a fraction of the emissions compared to an incinerator," said Greer.

Ray said that the ash produced in the waste-to-energy process can be used to manufacture materials such as the concrete used in paving streets.

"Any sort of refuse can be used in the plant, including sludge from the waste water treatment plant, plastics, construction waste, food, even rubber tires, which take up a lot of space in landfills," he said. "This will keep the waste out of the landfill. It's not a re-use program, but is a strong recycling program."

Even so-called "red bag" waste, which is bio-hazard waste produced by medical facilities that must currently be hauled off to centers equipped for that type of disposal — sometimes to another state — can be used in the waste-to-energy plant, said Ray. A few materials, such as very hard metals, could not be processed, he said.

Another benefit of the waste-to-energy program, said Ray, is that companies and facilities such as San Juan Regional Medical Center would be able to pay YESCO to have their waste incinerated, which could reduce their waste-removal expenditures.

The waste-to-energy units range from as small as a 500-kilowatt system, up to a two-megawatt system.

"We're looking at a one-megawatt system," he said. "We're already getting one megawatt of power from hydro and one megawatt from solar, and that's already giving us 31 percent of our power. If we could get ... 18 percent of power from the waste-to-energy unit, that would mean that 40 to 50 percent of our power would be produced by renewable energy."

Between seven and 15 jobs would be created to run the plant, which would operate seven days a week, he said.

As for the city's obligation if the plant came to town, Ray said it would operate as a separate business, and the city would only need to approve a lease and power purchase agreement. The current location being considered for the waste-to-energy plant is near the current wastewater treatment plant.

"The company would set up all of their own contracts, and we'd just need to have a power line going out from the plant to our current (electric) system," said Ray.

The next step for making the plan a reality, said Ray, is for city officials to tour an existing YESCO plant to see first-hand how turning waste into energy works.

"If it materializes, it could be phenomenal," said Ray. "I see it as an economic stimulus, plus it would further Aztec's goals to become environmentally-friendly and reduce our carbon footprint on the Earth, while at the same time create a new energy source for the city. It would be a win-win for everyone."

Leigh Black Irvin is the business editor for The Daily Times. She can be reached at 505-564-4621. 

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