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April 24, 2019

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Wood: Not the renewable energy some had in mind

State requirement prompts experimental mixing with coal


Sam Morris

NV Energy project manager David Sims shows some of the 750 tons of waste wood that will be burned with coal in the 30-day test.

NV Energy Tests Wood

NV Energy is testing out a new source of renewable energy: wood. The wood comes from trees that were cut for fire control in an Arizona national forest, and burning it emits less harmful sulfur into the environment than the coal that is traditionally burned.

Wood-coal mix

A payloader mixes wood chips with coal at NV Energy's Reid Gardner Station coal-fired power plant Wednesday, Nov. 4, 2009 near Moapa.  Launch slideshow »

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Beyond the Sun

When people talk about renewable energy, many mean the latest in clean-energy technology, not a fuel that was pioneered by cavemen.

But for NV Energy, what’s old is new again.

At the Reid Gardner coal plant about 50 miles northeast of Las Vegas, the utility last month began mixing wood chips with the coal burned to produce electricity at the plant.

If it works the way the company hopes, NV Energy intends to use the wood-coal mix to qualify the power plant for a bit of renewable energy credit, another step toward meeting the state’s mandates for increasing the use of renewable energy.

That’s right, NV Energy may have a coal plant classified as producing at least some of its energy from a renewable source — biomass fuel. Biomass is biological material derived from living or recently living organisms. That includes organic garbage, alcohol fuels and wood.

The state renewable energy portfolio standard — NV Energy must produce 25 percent of its electricity using renewable resources and energy efficiency measures by 2025 — allows the use of biomass to generate electricity. But state lawmakers said they hadn’t intended that to mean burning wood in coal plants.

“I don’t think we contemplated it this way,” said Randolph Townsend, the senior GOP state lawmaker on renewable energy issues. “We’d prefer it was just a biomass capacity, not mixed with something that’s not renewable. That defeats the purpose, which is to encourage and incentivize renewable activity.”

But that was about as critical of the NV Energy plan as the Washoe County Republican was willing to get. Townsend said he figures this is a more environmentally friendly way to use the coal plant until clean renewable energy becomes more economically feasible.

And some environmentalists agree — as long as this is just a stopgap.

“While this might be a workable step, we really need to keep our eyes on the prize of clean, renewable energy that we have a lot of here in Nevada,” said Launce Rake, spokesman for the Progressive Leadership Alliance of Nevada.

Burning biomass of nearly any form could reduce a coal plant’s greenhouse gas emission by up to 25 percent — but a coal plant is still a coal plant, he noted.

“One concern I know a lot of people have is: Does this just extend the life span of coal? It’s not ‘clean,’ even if you clean it up a little.”

NV Energy never intended wood burning to be an environmental measure, said David Sims, the utility’s director of project development. The wood chips are expected to have only a small effect on emissions.

“We were led by a desire to meet the renewable mandate,” Sims said. “Our primary purpose was to demonstrate a low-cost renewable energy.”

Although wood char has been incorporated into American coal plants for several years, feeding raw wood into the furnaces is relatively new. NV Energy got a permit from the state Environmental Protection Division to burn the blend for 30 days to see how it affects emissions and whether the plant would need to be modified to make the most efficient use of the fuel blend. The company also wants to see how much wood it can incorporate into the mix without decreasing generating capacity. The test began Oct. 19.

“We’re going to evaluate everything — the efficiency of the fuel, emissions, the cost per kilowatt hour and the cost per ton of wood material,” Sims said. “Once all those numbers are crunched we’ll be able to determine if this is a program we want to continue.”

So far, the company has determined that, to avoid clogging the plant, the wood chips need to be chopped into much smaller pieces than the half-inch bits that arrived. The utility contracted with the Moapa Paiutes, who have a wood pulverizer on their tribal land near Reid Gardner, to do the work. And so far the plant has been able to effectively burn a wood-coal mix with 5 percent raw wood. Sims said that might be the highest amount of raw wood that could be used.

Because of that the company doesn’t expect that incorporating wood into the coal plant will produce enough renewable energy to meet the state portfolio standard. But if the company can do it in a cost-efficient way, it would be foolish to pass up the opportunity, Sims said.

“We’re looking at this because we need to meet that portfolio standard,” Sims said. “We could build a biomass plant, but that would be expensive and the cost would be passed on to ratepayers ... We’re trying to make the best use of the materials and facilities we have at hand.”

But isn’t this process burning up trees that would otherwise convert carbon dioxide back to oxygen for us?

Well, the 750 tons of wood chips that will be used in the test project come from a section of Northern Arizona’s Kaibab National Forest that fire swept through three years ago. The burn zone is being cleaned by a number of small contractors organized through the nonprofit Rural Life Foundation Stewardship Center, based in Utah.

Contractors mill and sell what they can as lumber, and the scrap is chopped up into half-inch pieces and sold to mulch producers and power plants such as Reid Gardner to be burned as fuel.

There are many uses for waste wood gathered in national forests and on private land, but with all the forest fires, projects to eradicate invasive species, and new transmission lines being built in the West, there is plenty of waste wood to go around. If companies can’t find a buyer, the scrap is often burned on site.

That’s worse for the environment and air quality than trucking it 150 miles to Moapa and burning it in the coal plant.

There, the facility’s scrubbers and filters remove much of the particulates and other air pollutants before they make their way into the atmosphere. The test at the Moapa area plant should determine exactly how much pollution is released, but Sims said the company expects it will be much less than burning the wood in the open or letting it decompose, which would release methane, which traps more heat in the atmosphere than carbon dioxide does.

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