Biomass in the making

In this 2017 file photo, a machine shoots wood chips into the back of a truck during a tree thinning operation in the Kaibab National Forest. APS recently released a request for proposals that would use biomass, usually in the form of wood chips, from Arizona forests to generate a small portion of the energy the utility sends to customers around the state.

Arizona Public Service has determined that assisting the Arizona Corporation Commission’s policy of using forest byproducts for energy generation is financially feasible.

The decision could help clear the Four Forest Restoration Initiative’s problem of having too much forest thinning byproducts.

In a letter sent to the Arizona Corporation Commission, APS said they could feasibly convert a power generator at their Cholla Power Plant to burn forest thinning byproducts or biomass. The utility company also said the determination depends on how private businesses respond to 4FRI’s next request for thinning proposals. 4FRI is currently working on the next phase for their large-scale forest thinning project to help reduce the risk of catastrophic wildfires in northern Arizona forests.

APS expects the conversion could be completed by 2022 and cost approximately $205 million, according to the study. The study also says the Cholla generator capacity could exceed the commission’s request for 60 megawatts of power to 83 megawatts.

Some expect that a final decision to convert the commission’s energy generation to biomass fuel would add $1 to $4 to customers’ bills, although 4FRI stakeholders counter that this cost would be much less than the costs of massive wildfire.

APS did not indicate its official stance on the commission’s investigation into replacing coal generated energy with biomass, but previously wrote to the commission that the utility company would suggest moving forward on the conversion if it was more cost-effective than other options at a date after the release of the study.

4FRI officials have said their next request for proposal is in the final stages of review, and hope to award one or more large-scale, 20-year stewardship contracts this year.

Last year, the action was halted, citing a lack of information on the value and amount of trees that would be covered in the new contracts.

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APS said in their study that if the conversion were implemented, the utility company would likely issue requests for proposals (RFPs) to transport biomass to their facility.

“APS believes that concurrent release of the USFS RFP and an APS fuel supply RFP will increase the opportunities for both the Forest Service and APS," according to the study.

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Cholla's operation

Cholla is expected to close its coal generation in 2025, according to APS spokesperson Suzanne Treviño. Its coal is shipped from the El Segundo Mine in northwest New Mexico.

Currently, Cholla employs about 200 people including contracts. APS estimated in their study that a generator conversion would require 90 direct and 19 indirect logging and transportation jobs and over 800 direct and 600 indirect temporary construction jobs.

APS owns the plant and operates two of the four generator units, while PacifiCorp owns their third unit. The fourth unit was retired from use in 2015.

PacificCorp receives electricity from APS in the winter to serve Pacific Northwest customers, and APS gets power in the summer to meet Arizona customers’ peak usage, Treviño said.

The unit that was evaluated for conversion was the smallest unit, currently generating 116 megawatts through coal.

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Scott Buffon can be reached at sbuffon@azdailysun.com, on Twitter @scottbuffon or by phone at (928) 556-2250.


Senior Reporter - Cops, Environment

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