WILLIAMS, Ariz. — The Arizona Corporation Commission is aiming to jump start the thinning of Arizona forests with a recent decision that will require the state’s utilities to produce 90 megawatts of energy annually from forest biomass. However, the commission must still adopt a final rule, with many key details still undetermined.
The Forest Service and loggers said efforts to treat Arizona’s forests are being bottlenecked by the massive amount of biomass produced with thinning. Forest biomass refers to pine needles, branches, treetops and small trees that must be removed from a forest during tree thinning, but aren’t marketable in the lumber industry.
“Forest restoration, while it reduces the risk of wildfires, also produces additional biomass which must be consumed by other users or it must be burned in large piles in the forest,” said Art Babbott, representing the Coconino County Board of Supervisors in a letter to the Arizona Corporation Commission.
In 2010, the U.S. Forest Service implemented the Four Forest Restoration Initiative (4FRI) to improve local ecosystems and decrease the potential for catastrophic wildfire events across the Coconino, Kaibab, Apache-Sitgreaves and Tonto National Forests. The goal is to treat 50,000 acres of forest per year through mechanical thinning and prescribed fire, according to the 2017 Four Forest Restoration Initiative Strategic Plan.
But according to the 4FRI Stakeholder group, just 15,000 acres of forest have been treated annually in the White Mountains area and 1,500 acres in the San Francisco Peaks area. Stakeholders attribute better success in the White Mountains area because of the proximity of Novo Power, which operates a 27 megawatt biomass power plant in Snowflake, the only one in Arizona.
The stakeholder group contends the backlog of biomass has created a bottleneck for the restoration initiative. Traditionally, piling and burning the biomass has been the way to dispose of the logging biomass, but as the biomass piles get larger, pile burning creates collateral damages to adjacent trees and can result in soil sterilization and poor air quality.
“Restoration cannot be scaled up unless field biomass removal and disposal is scaled up,” the group said in a statement to the Arizona Corporation Commission. “With forest restoration ramping up to landscape-scale (50,000 acres per year), 4FRI will generate over 1 million green tons of logging biomass every year. This is simply too much biomass to pile and burn.”
In May 2017, Arizona Corporation Commissioner Boyd Dunn requested the opening of a docket to explore the role of forest bioenergy in Arizona as a means to use the woody biomass generated from thinning to create energy for the grid.
The Commission’s interest in forest bioenergy stemmed from recent federal directives to develop policies that recognize the benefits of this resource and encourage its use by generating power, encouraging responsible forest management and reducing the risk of wildfires.
The Commission ordered APS to conduct a study and assess the use of forest bioenergy - taking into consideration forest thinning activities, costs, environmental benefits and adjustments to APS’s revenue requirement to assist the Commission in its assessment of the issue.
APS retained Black & Veatch to perform the technical portion of the assessment.
Black & Veatch found the benefits of forest bioenergy projects are significant as it relates to the environment. Reducing conditions that lead to wildfires is not only important for the safety of Arizona residents, wildlife and commercial infrastructures, but from a utility perspective, mitigating wildfires also protects transmission lines that can be damaged from heat, smoke and flames.
They also found bioenergy projects improve watersheds to promote healthy landscapes, promote industry and employment opportunities and could result in CO2 emission reductions.
Along with the benefits, Black & Veatch found several risks associated with bioenergy projects. The main risk is whether the forest industry can expand fast enough and consistently over time to assure a 20-year constant fuel supply. Without an assured fuel supply, it could be difficult to secure purchase power agreements and financing for the construction of new plants.
Black & Veatch also determined APS revenue requirements could increase by $57 million to $1.03 billion and residential customers would then experience an increase in their monthly bill from $1.54 to $4.13, although APS acknowledged there could be an associated cost savings with fewer or less intense wildfires.
In the study, Black & Veatch determined that 1,221,000 acres will be approved for thinning by 2021, which equates to 61,000 acres of forest per year. From this, approximately 28 million green tons of biomass would be available for bioenergy.
Black & Veatch looked at the options for converting forest biomass to electric energy and came up with three options. The first is to continue the operation of the existing Novo BioPower plant in Snowflake, Arizona which has been commercially operating since 2008.
The second option is to convert existing coal plants to co-fire or direct-burn biomass. These include evaluating plants such as the Cholla Power Plant near Joseph City and the Coronado Generating Station near St. Johns, Arizona
The third option is to construct new forest bioenergy facilities which potentially could produce 60 MW of power which could offset the transportation costs associated with present 30 MW plants.
Black & Veatch focused the study on biomass combustion technologies for conversion of woody biomass to electric power. They compared potential locations for plants in Alpine, Camp Verde, Payson, Williams and Winona. Based on analysis, Payson and Winona were chosen as the best economic locations based on various factors. At the highest utilization scenario, up to 70 to 75 percent of the available biomass could be consumed by these facilities.
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