Just add water: AZ pushes for 'bioreactor landfills'

New technology could speed conversion to other uses but may pose hazards
2012-12-29T00:00:00Z 2014-07-15T17:49:53Z Just add water: AZ pushes for 'bioreactor landfills'Tony Davis Arizona Daily Star Arizona Daily Star
December 29, 2012 12:00 am  • 

More liquids - and, critics fear, some illegal hazardous wastes - could be coming to Arizona's 39 garbage landfills if a new technology for treating landfill liquids wins federal approval.

The Arizona Department of Environmental Quality wants to make this the 15th state nationally to secure Environmental Protection Agency permission to start issuing permits for what's known as "bioreactor landfills." They use liquids to react with garbage and speed the decomposition of methane gas that radiates from landfills everywhere.

That could extend landfill lives significantly, say backers, who include the operator of the city of Tucson's Los Reales Landfill as well as some private landfill operators.

In other cases, bioreactor landfills could speed closure and transition of landfills to other uses, ADEQ said.

But the proposal is drawing significant opposition from environmental groups, U.S. Rep. Raúl Grijalva and three Arizona Democratic legislators who fear it will increase the risk of contamination at landfills.

Their fears stem from a series of tests over the past three years that show samples of 5 to 10 percent of liquid wastes taken to several Arizona landfills - none in Tucson - contained 3 to 5 percent hazardous wastes. Those are typically barred from solid-waste landfills.

Opponents are also worried that these landfills would require more water use in one of the country's most arid states. They're also worried that some of the methane would seep into the air, adding to the load of greenhouse-gas emissions now blamed by many scientists for climate change.

Yet, backers say the speeded-up methane production could clear the way for transforming the gas into energy, to power vehicles and electricity plants. The idea has economic benefits, including numerous construction jobs as well as hiring of permanent employees, wrote Leisa Brug, Gov. Jan Brewer's energy-policy adviser, to EPA.

If this technology is approved for Arizona, the city of Tucson's Environmental Services Department would "absolutely" be interested in possibly using it at Los Reales on the southeast side, said Andrew Quigley, the department's director. Its use would depend on the amount of water needed and how much the city has available, said Quigley. He will "guarantee" that the city won't use clean groundwater or Central Arizona Project water for this process.

"This is an opportunity to add another tool to our landfill toolbox," Quigley said. "I don't create the material in our landfill. It's already there. It's going to decompose, probably over centuries. I'd like to speed the process up by doing it right, so I don't have to take care of it for eons."

Quigley said he'd also look forward to using the extra methane to power natural gas-powered trucks, of which the city plans to buy 13 next summer; or to sell to Tucson Electric Power to replace coal at its Tucson power plant.

But the technology's water use was attacked in letters to the EPA from the Sierra Club, the Tucson Audubon Society, the Coalition for Sonoran Desert Protection and the Arizona League of Conservation Voters, along with state Rep. Bruce Wheeler of Tucson and two Phoenix legislators, among others.

In 2002, the EPA noted that in conventional landfills, garbage typically contains 20 percent moisture, and that figure could be lower in arid areas. A bioreactor landfill requires a minimum of 40 percent liquids and up to 70 percent, the EPA wrote.

Such water use doesn't belong here as this region suffers through a drought stretching nearly 15 years, with more drought forecast, wrote Paul Green, director of the Tucson Audubon Society, and Christina McVie, the society's conservation chair, in a Dec. 18 letter to the EPA.

"Just to serve our residents potable water, we import it 335 miles from the Colorado River," wrote Pima County Supervisor Richard Elías in a Dec. 12 letter to the EPA. "We can ill afford to pour hundreds of thousands of gallons of water a day into experimental landfill bioreactors."

ADEQ said it will consider these landfills' moisture needs in reviewing future permit applications. Tucson's Quigley said the city would use only contaminated water that it currently treats from an older, inactive, unlined part of the landfill; the active section is lined.

That 300,0000 gallons a day of contaminated water is tainted with low levels of TCE and PCE, an industrial and a dry-cleaning solvent, respectively. Once pollutants are stripped from the water, it's injected into the ground or used for dust control, Quigley said.

"Could we take some of that water and mix it with trash and start the methane decomposition sooner?" he asked. "If ADEQ or EPA allows this in Arizona, that's when we'll start looking at opportunities for Los Reales," he said, adding that the technology is probably two years off here.

But in his Dec. 18 letter to the EPA, Grijalva wrote that currently Arizona landfills handle about 25 million gallons of liquid waste annually. If 5 percent of a small sample of that is tainted with hazardous materials, that means 12.5 million gallons of liquid waste has been dumped in Arizona landfills in the last 10 years, he wrote.

The bioreactors' higher moisture content and weight increase risks to groundwater, and there must be guaranteed safeguards, Grijalva wrote. "That can only be accomplished by testing 100 percent of all incoming loads of liquid waste."

In response, ADEQ said that all state approvals of city garbage landfills include prohibitions on taking hazardous wastes.

"The department will continue to work with owners and operators to ensure that regulated hazardous waste is not being disposed at solid-waste landfills and that human health and the environment are not being threatened," ADEQ wrote to the Star.

Tucson's Quigley said he would be in favor of expanded testing of bioreactors. At Los Reales, companies that bring wastes are already asked for certifications from a testing lab as to what's in them, he said.

"The same protocols would apply to liquid-waste haulers," Quigley said. "We would not intend to accept hazardous-waste liquids."

On StarNet: Read more related stories at azstarnet.com/news/science/environment

"This is an opportunity to add another tool to our landfill toolbox. I don't create the material in our landfill. It's already there. It's going to decompose, probably over centuries. I'd like to speed the process up by doing it right, so I don't have to take care of it for eons."

Andrew Quigley,

Tucson Environmental Services Department director

Contact reporter Tony Davis at tdavis@azstarnet.com or 806-7746.

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