Experts discuss biomass's place in the U.S. power industry

By Anna Austin | November 10, 2011

The U.S. electricity industry includes approximately 300 gigawatts of coal-fired power, generated from large-scale power plants with electric capacities of anywhere from 200 to 4,000 megawatts (MW). Most of these plants can easily use biomass to some degree depending on the age of the boiler, the combustion process and other factors, but nearly all of them could burn 2 percent biomass with no modifications, according to Chris Blazek of Enviro-Burn Inc. That would result in an additional 6,000 MW of renewable electricity.

During a Nov. 10 webinar hosted by POWER Magazine, Blazek discussed the potential, drivers, and limitations of cofiring biomass at U.S. coal plants. He pointed out that according to U.S. Energy Information Administration projections of renewable energy growth, biomass represents the greatest potential, compared to other renewables, during the next decade.

One way to increase biomass energy is by utilizing biomass at coal plants, which can be done a couple of different ways. One is blending small amounts of biomass in with coal, and that can be done right at the coal mine. “In some cases the mines are located right near the plant,” Blazek said. “It can be done with only some small changes to the material handling system.”

When increasing the amount of comilled biomass to 10 to 15 percent, requires higher capital costs and a few more adjustments to the plants. “Many boilers require a very fine grind,” Blazek said. Cofiring, or separately injecting biomass and coal into the plant, is more expensive, but considerably cheaper than building a stand-alone biomass power plant, according to Blazek.  

Existing power plants have been designed for a specific fuel type, so even changing coal types requires some modifications to the boiler. “So it can be a relatively large change for the plant, depending on how much biomass you’re introducing,” Blazek said. “Cofiring represents a low cast way to introduce biomass into the power industry and produce a lot of renewable power, reduce CO2, and other emissions.”

Following Blazek, fellow presenter Amanda Hamsley Lang of Forisk Consulting LLC discussed the current wood market and project development. She said the total amount of existing and proposed projects in the U.S. would require about 136 million green tons of wood each year, however, that number is reduced by 54 percent when Forisk uses its tools to screen projects to determine whether it is likely they will succeed. “When using the technology screen, an example of one that would not pass is a cellulosic ethanol plant, because there are no commercial-scale plants running today,” Lang said.

The second screen used evaluates where a project is in the development process. “If a project has secured two or more of the necessary milestones that it needs to become operational, such as a site through a lease or purchase, or an air quality permit, that is two they would need to succeed,” Lang said. She added that almost 50 percent of wood-using energy projects are proposed or under construction rather than operating. As of October, 179 were pellet projects, followed by wood-to-electricity projects, according to Lang.

In addition to Blazek and Lang, Marco Castaldi of Columbia University’s Department of Environmental Engineering presented during the webinar. He discussed the fundamentals of coal and biomass gasification, specifically addressing the boundaries where highest efficiencies are obtained.