WWCS or "What Would Cliff Say?"

It might start off like this:

What Would Cliff Say (WWCS): I see that the House of Representatives just passed "The American Clean Energy and Security Act of 2009." I'll tell you what I think. Have you heard of co-firing coal power plants with wood and forest by-products?

(Most of us would probably have to say that, no, we haven't heard of such a thing. If we didn't know Cliff too well, we'd probably ask some questions ...)

How much electricity do you think could be supplied by co-firing all the coal plants in the United States with 10 percent wood biomass?

WWCS: Well, by my calculations that would be about 30 GW That probably doesn't mean much to your average layman, but it's about the amount of electricity consumed in New England.¹

How much wood biomass per year would be needed if all the U.S. coal plants co-fired with 10 percent wood biomass?

WWCS: You'd be talking over 140 million dry tons of your wood waste, meaning forestry byproducts.

Jeez, Cliff, that's a lot of wood.

WWCS: That would be about the weight of 38 Empire State Buildings or 1,740 Eiffel Towers!²

How many acres of timberland is that?

WWCS: Is this how many acres needed to get about 140 million tons of wood? Well, the United States has about 500 million acres of timberland. ³ That's about 3 times the size of the State of Texas!⁴ But, you see, that's not all going to be used for biomass. After you subtract out your currently used fuel woods, your timber used by the forestry industry, and some other things, you get almost 200 million acres of timberland that you could use for renewable wood biomass. That's just a little larger than Texas.

How about transporting all that wood biomass …?

WWCS: A single train carrying the total annual biomass usage would be over 18,000 miles long or more than 6 times the distance between Seattle, Washington and Jacksonville Florida.⁵

Do we have enough wood biomass to co-fire all those coal plans?

WWCS: Well, it seems to me we have just about enough. You see, the United States has just over 310 GW of coal-fire capacity. Let's assume 10 percent of that could be fired with wood biomass. That's about 31 GW. My calculations tell me that the United States can produce 35 GW using our current forest resources. 'Course, I've left out your grass clippings and tree trimmings, since we're just talking about forestry products.

How did you come up with all of these figures?

WWCS: Well, let me draw it out on this napkin, here:

According to the U.S. Departments of Agriculture and Energy (the study)⁶:

"The land base of the United States encompasses nearly 2,263 million acres, including the 369 million acres of land in Alaska and Hawaii. About 33 percent of the land area is classified as forest land, 26 percent as grassland pasture and range, 20 percent as cropland, 8 percent as special uses (e.g., public facilities), and 13% as miscellaneous uses such as urban areas, swamps, and deserts.

"Currently, more than 75 percent of biomass consumption in the United States comes from forestlands. The remainder includes biobased products, biofuels and some residue biomass comes from cropland.

"U.S. forestland consists of 749 million acres, of which 504 million acres is classified as timberland, capable of growing 20 ft³ per acre of wood annually (3 times the size of the state of Texas). 168 million acres of forestland is incapable of growing 20 ft³ per acre of wood annually. The remaining 77 million acres of forestland is legally reserved from harvesting.

"We currently remove less forest inventory than net annual forest growth. For example, in 2010, forest removal will be less than one-half that of forest growth."

Figure 1
Forest Density in the United States
(Source: U.S. Forestry Service)

Using figures from the study, and subtracting out current usage, urban waste (grass clippings, tree trimmings in cities) and future usage by the forestry industry, we arrive at 144 million dry tons of wood biomass available for future coal plant co-firing.

Figure 2
144 Million Dry Tons Available for Future Co-firing⁶

Converting this tonnage into electricity generation equates to 35 GW. This assumes an average coal plant capacity utilization of 80 percent, an average coal plant heat rate of 10,000, and average heat content of wood biomass of 8,439.5.⁷

U.S. coal-fired generating capacity, not currently co-fired, is about 310 GW. 10 percent of that capacity is 31 GW.

So we've got enough wood biomass with some to spare.

This IssueAlert article attempted to look at one aspect of co-firing possibilities—potentially available supply of forest by-products biomass. It does not intend to predict shortages, surpluses, costs or practicalities of conversion and co-firing. Rather it attempts to put a perspective on the available supply of wood biomass for coal plant co-firing purposes.

Currently 75 percent of biomass generation is fueled by forestry and urban waste products. In the future, not all coal-fired power plants will co-fire with wood biomass. There will be more options to meeting the needs of future of renewable power resources, greenhouse gas reduction, and renewable portfolio standards than building new biomass direct and co-fired power plants. The analysis provided here shows that biomass is a promising resource, but there will be practical limits to how much this resource will become of our energy supply mix.

¹ According to the EIA, the average U.S. residence uses more than 11,000 kWh annually. Assuming an 80 percent capacity factor for coal plant generation, this equates to 2.4 million homes.
² According to www.stupiquestion.net, the Empire State Building weighs 365,000 tons. The Eiffel Tower weighs 8,045 tons.
³ Source: "Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply," Oak National Laboratory, U.S. Department of Energy)
⁴ According to www.wikipedia.org, Texas has 268,820 square miles or 172,044,800 acres of land mass.
⁵ According to FreightCar of America, a woodchip railroad car can carry 212,900 pounds (106.45 tons) and is about 72 feet in length. A single train carrying the total annual biomass usage of 144 million dry tons would require 1,352,747 cars.
⁶ Source: "Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply," Oak National Laboratory, U.S. Department of Energy)
⁷ Source: US Department of Energy, Energy Efficiency and Renewable Energy, Biomass Feedstock Composition and Property Database (May 15, 2004)