APS will try to switch coal power plant to burn wood from forest thinning, possibly cutting wildfire risk
Arizona Public Service Co. will try to save some jobs near Holbrook and reduce wildfire risks at the same time by testing whether pine trees can be substituted for the coal that is burned at the Cholla Power Plant.
The coal plant is scheduled to close in 2025, and while converting it to natural gas was considered, that is not being pursued, APS officials said.
About 200 people work at the plant in Joseph City, along Interstate 40 and the Little Colorado River.
"A conversion at Cholla would ultimately assist in forest thinning, thereby reducing wildfire potential, ensuring forest health, and protecting our watersheds," APS Vice President of Regulation Barbara Lockwood said in a March 20 letter to regulators.
Forest biomass is wood chips made from forest trees. Regulators at the Arizona Corporation Commission in December approved a policy to embrace forest biomass as a renewable-energy technology.
Arizona already has one small power plant near Snowflake fueled by forest biomass, with a capacity of 24 megawatts. That's enough power to supply about 6,000 homes when the plant is running. APS buys half the power from the plant and Salt River Project takes the other half.
The Arizona Corporation Commission biomass policy suggests utilities get 60 megawatts or more from the forest.
APS continues to run two units at Cholla after closing one in 2016. The fourth unit at the plant is owned by PacifiCorp, which similarly plans to close in 2025.
It's unclear how many jobs would remain should the plant convert to coal, but it's unlikely the full staff would be needed because only one of three generators would be converted.
APS is considering converting one unit that produces about 117 megawatts of capacity when burning coal, but would probably only produce about 70 or 80 megawatts as a biomass unit, because that fuel doesn't burn as hot, Burke said.
Helping reduce fires
The ponderosa pine forests in Arizona are severely overgrown from more than a century of fire suppression and livestock grazing, which eliminates the frequent, small fires that kept the tree growth in check.
Now many parts of the state's forests are choked with thousands of small trees per acre, and combined with drought, they pose severe wildfire risks.
When fires spark, they tend to ignite megafires that burn through the crowns of trees, rather than just burning up the smaller trees and grass.
The U.S. Forest Service can pay to cut and burn the excess trees, but such thinning projects are expensive. Finding a commercial use for the small trees has been a challenge, which makes burning them for electricity attractive.
After a 60-day test, APS will update the Arizona Corporation Commission regarding whether converting the coal generator to burn biomass would be cost efficient, officials said.
"Part of what we are trying to do here is explore all options," said Jeff Burke, APS resource planning director.
Last year, APS issued a request for proposals from biomass power to see what companies might be considering such projects.
"We kind of had limited response," Burke said. "The response we got back was fairly costly."
That prompted APS to rethink other options, he said.
What about carbon emissions?
Like many power sources, one of the main concerns with burning pine trees is the greenhouse-gas emissions that such plants generate.
The U.S. Environmental Protection Agency considers the electricity from forest biomass to be carbon neutral and to not contribute to climate change. But there is some debate on the subject.
The Sierra Club's national guidelines on forest biomass indicate the energy can be considered "a renewable source of energy that does not aggravate global warming because the carbon involved is functioning in a short cycle, and regrowth (of the trees) balances the emissions."
But the Sierra Club's guidance warns that not all forest biomass projects are run responsibly.
"We believe that biomass projects can be sustainable, but that many biomass projects are not," the environmental group's guidelines say. "We are not confident that massive new biomass energy resources are available without risking soil and forest health, given the lack of commitment by governments and industry to preservation, restoration, and conservation of natural resources."
And the Grand Canyon Chapter of the Sierra Club wrote to state regulators in December opposing additional forest biomass projects.
"Frequently the costs and the carbon emissions of transporting biomass are not considered," Grand Canyon Chapter Director Sandy Bahr wrote. "Both can be substantial. Especially at a time when truly clean renewable sources such as solar and wind are cost-competitive with other energy resources, we question proposals to subsidize biomass."
Arizona Corporation Commissioner Andy Tobin, who has been pressing for updated renewable-energy rules that incorporate more forest biomass, has frequently argued that burning trees to generate power might create carbon emissions.
Tobin notes that the alternative has been to simply cut and burn such overgrowth in piles during cool seasons when the threat of sparking a wildfire is minimal, resulting in the same emissions being released but without generating electricity.
APS would need help
APS fuels the Cholla plant with coal from a New Mexico mine. Should it convert to biomass, the company would need a partner to supply it with fuel, Burke said.
"APS is not in the business of procuring forest biomass for fuel," Lockwood's letter said.
Securing fuel has been a challenge for the existing biomass plant near Snowflake, but Burke said he expects the Forest Service to issue a large request for proposals for companies seeking access to federal forests in the next year.
That request for proposals would be critical to making such a project work, he said.
SRP tried something similar
In 2016, SRP tested burning forest biomass at its Coronado Generating Station coal plant near St. Johns in northern Arizona.
But rather than convert the plant, SRP burned the biomass with coal.
Two initial 10-day tests showed the idea worked, but that additional testing is needed, SRP spokesman Jeff Lane said.
While no modifications were made to Coronado for the test, the plant would need some upgrades if it were to burn wood all the time, he said.
SRP still is evaluating whether those upgrades would be cost efficient, he said.
SRP also is involved in the request for proposals expected this year from the U.S. Forest Service for projects that will help thin the forest.
"The intent is to support existing industry and attract new sustainable industry to significantly increase the pace and scale of restoration while creating jobs, restoring forests, and protecting communities and downstream water supplies," Lane said.