SRP to test burn forest debris at coal plant

By Salt River Project | July 15, 2016

Salt River Project is exploring the feasibility of using forest debris as a supplemental fuel at its Coronado Generating Station in St. Johns, Arizona, to improve the health of Arizona's forests and watersheds.

CGS workers are scheduled to test burn more than 2,600 tons—or about 250 acres—of forest debris biomass at the plant over a 20-day period beginning in the fall or early winter.

Biomass will be only used on a very limited scale at CGS for this test burn—the first of its kind in Arizona in which forest debris will be co-burned with coal—and this limited project will not require any permanent modifications to the power plant.

The test burn will help SRP understand whether some of the technical challenges of burning forest waste at a sophisticated coal-fired facility can be adequately addressed. In the forest-restoration process, large trees are harvested, leaving behind tons of low-value woody biomass that would otherwise be placed in large piles and burned—and often creating emissions and smoke for local residents.

"While there are many hurdles to overcome, if we are successful in making CGS a potential receiver of forest-clearing materials, it would provide significant assistance to keeping our forests healthy while reducing the risk of catastrophic wildfires," said SRP Chief Water Resources Executive Dave Roberts.

Forest waste is not a fuel of choice for utilities because it is less efficient in producing heat to generate electricity, is generally more expensive than traditional resources and could adversely impact vital equipment such as the plant's boiler or fuel-delivery lines. Roberts said that if the test is successful, the potential positive impact on Arizona's forests could outweigh the challenges associated with burning tree and brush clippings at CGS.

"The test of biomass planned by SRP is a tremendously important and innovative step in responding to climate change, providing for forest health and potentially reducing wildfire risk," said Cal Joyner, Forest Service Southwestern Regional Forester. "Finding economically positive uses for the huge volume of biomass on the National Forests is a major barrier to overcome in the long-term protection of critical watersheds in northern Arizona."

Reducing the risk of wildfires in northern Arizona will reduce erosion, sedimentation and ash in the Salt and Verde river watersheds, protecting vital water supplies for residents, businesses and agriculture in the greater Phoenix metropolitan area as well as rural Arizona communities, Roberts said.

SRP will work closely with its agency partners, including the U.S. Forest Service and the state of Arizona, to address funding for the test burn as well as the forest-thinning activities and the transportation of the materials to CGS.

According to Jeff Whitney, State Forester-Department of Forestry and Fire Management, "Forest thinning is a priority to accomplish a number of related natural resource management objectives across all lands in Arizona, whether private, tribal, state and federal lands. The potential to expand the use of forest and woodland management byproducts that are currently not being used—generally referred to as 'biomass'—through 'wood to energy' is an important facet of our statewide strategy."

CGS, owned and operated by SRP, was completed in 1980 and uses coal as a fuel to generate electricity from two 400-MW units for SRP customers in Phoenix metropolitan area. SRP recently completed a $470 million project at the plant to install new emission-control technology that further reduces sulfur dioxide, nitrogen oxide and mercury emissions.

SRP is a community-based, not-for-profit public power utility and the largest provider of electricity in the greater Phoenix metropolitan area, serving more than 1 million customers. SRP also is the metropolitan area's largest supplier of water, delivering about 800,000 acre-feet annually to municipal, urban and agricultural water users.