The Cholla Power Plant.

Is burning biomass made from wood scraps better for the planet than burning coal?

Certainly, it could rescue efforts to restore overgrown Arizona forests if the Arizona Corporation Commission follows through on a proposal to require utilities like Arizona Public Service to generate at least 60 megawatts of power from biomass every year. Advocates say such a mandate is critical to salvaging the Four Forest Restoration Initiative (4FRI).

APS has undertaken a 60-day study of the impact of converting one of its generating units that burns 70-80 megawatts from coal-fires at the Cholla Power Plant near Joseph City to biomass.

Clearly, this could salvage 4FRI and protect forested communities like Payson and Show Low from the rising plague of high-intensity crown fires. The Forest Service last year spent $2.4 billion fighting fires, which didn’t prevent billions of damage and more than 85 deaths due to uncontrolled wildfires.

That’s why Eastern Arizona Counties Association Executive Director Pasquel Berlioux has urged the Arizona Corporation Commission to impose the biomass mandate, no matter what APS decides to do about Cholla.

“The overriding concern is that the ACC rule making MUST keep moving. In either case it is needed: for Cholla if the APS study shows that it is a lower cost alternative; or, for other alternatives, if Cholla is not the lowest cost.”

But would shifting to biomass burning also help reduce global warming and protect human health?

Already, APS has substantially reduced harmful emissions from the Cholla, coal-fired power plant. The Roundup previously reported on emissions figures from the four-unit power plant reported online by the Clean Air Task Force. Those numbers were based on 2006 emissions.

However, since then APS has shut down one unit and added pollution controls. APS figures show that in 2018 the power plant produced half as much carbon dioxide, 75 percent less nitrous oxides and 90 percent less sulfur dioxide as reported based on the 2006 figures.

The Roundup article also noted that the task force had concluded Cholla was the eighth-most-polluting power plant in the country, when actually it was in 2006 the eighth worst polluter when it came to coal waste impounded on the site. The task force also produced estimates of deaths and health problems caused by Cholla based on national models, not on an analysis of the plant itself. The big drop in emissions since the issuance of the task force report has dramatically reduced potential health effects.

Prior to launching the study of a conversion to biomass, APS had proposed converting the remaining units to less-polluting natural gas, in return for relaxing a federal requirement to put more pollution controls on the existing plant.

Environmental groups including the Sierra Club, Earth Justice and the National Parks Conservation Association protested the postponement of the proposed pollution controls on the grounds emissions from the power plant contribute to haze in 13 national parks, including the Grand Canyon and Petrified National Forest.

However, leaving thickets of small trees in the forest to fuel wildfires also poses a substantial health risk — even if it doesn’t burn through forested communities.

For instance, one study suggested premature deaths related to wildfire smoke will rise from an estimated 15,000 annually now to perhaps 40,000, although the estimates involve a lot of assumptions, according to the study published in GeoHealth, a journal of the American Geophysical Union.

A Stanford study published in Geophysical Research Letters estimated that biomass burning — including wildfires, cook fires, brush clearing and power plants, contribute to the premature deaths of 250,000 people worldwide each year. The total burned amounts to 39 billion tons annually.

APS officials said the studies they are undertaking will include some emissions estimates and if they are able to switch to biomass they would likely need to continue using some of the existing pollution controls. The controls that could be required would be dictated by the overall emissions estimates, which will be determined after additional environmental studies are completed.

Studies elsewhere suggest that biomass plants could produce about 70-80 percent fewer emissions than coal-fired plants, depending on pollution controls and other factors.

The proposal to convert Cholla injects the power plant into the heart of an ongoing debate about whether biomass burning counts as “renewable” energy in the same was as solar and wind energy.

The APS proposal is based on the assumption that burning wood scraps, saplings and the wood waste not usable in timber mills would count as a renewable, zero-carbon-emissions fuel.

This assumes the wood harvested from the forest would soon burn or decay anyway. By contrast, the carbon and other pollutants produced by coal and oil have been buried and out of circulation for millions of years.

The European Union has embraced biomass burning as a “carbon neutral,” renewable technology, with ambition targets to generate 20 percent of its energy from such sources by 2020. As a result, countries like the United Kingdom are importing millions of tons of wood pellets from the U.S.

However, calculating whether biomass is really “carbon neutral” depends on several assumptions. Clearly, it seems to apply to projects like 4FRI, with biomass removed in an effort to enhance forest health and reduce the number and intensity of wildfires. The remaining big trees take up more carbon, potentially locking it up for centuries. But the argument may not apply as well to clear cutting on a tree farm, which releases a flush of heat-trapping gases into the atmosphere. It can take a century for new trees to grow and remove an equivalent amount of carbon.

On the other hand, converting coal to biomass could not only reduce, but save jobs, according a study published in the scientific journal Joule.

The researchers studied the what would happen if we both converted coal plants to biomass and injected emissions into underground storage systems. The combination could not only retain 40,000 coal industry jobs, but create 22,000 new jobs in the forestry and transportation sectors in the U.S.

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