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Biocoal Options

A new future for small coal-fired plants.

Fortnightly Magazine - December 2010

units provide significant site-specific benefits, especially steam and voltage support. Both of these characteristics are highly relevant to management decisions involving these units.

Unlike the larger units, the management alternatives for these small units are quite limited. Because of their locational benefits, shut down (and the use of replacement power) is often undesirable. In general, it is difficult to import steam, chilled water or transmission support. Because of their size and location, capital investments such as natural gas repowering, coal gasification and carbon sequestration aren’t generally viable. Even conversion to burning raw biomass may be difficult because of needed capital investment or site constraints. As a result, most of these units continue operating in the current coal-burning mode, despite considerable economic, environmental and social challenges. Operators of many of these units are under considerable pressure to act because of the high cost of fuel; ground-level pollution and other local concerns; and global warming.

One emerging solution involves turning crop wastes into biocoal, a potential direct replacement for coal fuel in small power plants.

Crop-Waste Biomass

The past and present of the U.S. electric power industry belongs largely to fossil fuels—and coal in particular. But by most accounts, the future belongs increasingly to renewables. EIA projects that renewables will constitute 40 percent of the growth in electricity generation through 2035, and other estimates are even higher. 3 Among renewables, wind is currently dominant. Solar power seems to be favored for future growth despite its intermittency and cost issues. Geothermal power is also garnering increasing attention.

Biomass is one renewable resource that has received only a limited amount of attention, and not all of it positive. Most sources indicate that more than 500 million tons of biomass is produced sustainably each year in the United States (see Figure 4) . This includes waste wood from forestry, municipal waste, and crop residues from agriculture. 4 Someday, this biomass resource might be used to produce ethanol at a large scale. However, the dominant use of biomass for energy currently and in the near future is in power generation. When it comes to power generation, the 500 million tons in sustainable biomass could supply 30,000 to 40,000 MW of baseload capacity. This is a sizable fraction of the installed U.S. generation capacity, and is greater than the current U.S. operating base of all renewable power generation (excluding conventional hydro). Currently, there is well under 5,000 MW of operating biomass-based power generation.

To date, most of the limited attention paid to biomass has focused on wood. However, the dominant biomass resource isn’t wood, but is instead crop waste. The great bulk of this crop waste is corn stover and wheat straw. At over 200 million tons a year, crop waste alone represents a resource that could potentially fuel 15,000 MW or more of baseload power generation. And in many cases crop waste might be less controversial and more sustainable as a biomass resource than wood is. The resource estimate for available crop waste already reflects amounts needed for soil conditioning, livestock feed and other beneficial uses.

Interestingly, the