International Biomass Conference & Expo: Power utilities discuss biomass stategies

By Anna Austin
Posted May 6, 2010, at 9:45 a.m. CST

The future cost of CO2 is looming over power utilities. In order to avoid penalities and keep customer costs to a minimum, it's imperative that power utilities begin preparing for a carbon-constrained regulatory environment, according to Great River Energy Manager of Business Development Sandra Broekema.

Broekema and several other representatives of the Midwest's largest power providers presented during the general session panel at Biomass Magazine's International Biomass Conference & Expo in Minneapolis, May 4-6. Presenters shared each respective power utility's perspectives and strategies surrounding the use of biomass as a fuel source, as well as anticipated challenges and benefits.

GRE-a generation and transmission cooperative that serves 1.7 million people in Minnesota and western Wisconsin- has been working for quite some time to avoid future carbon expenses that will be imposed on utilities, said Broekema, costs which would be handed down to customers. "Looking at our generation portfolio, we have a fair amount of coal-fired generation which emits twice the CO2 footprint compared to a natural gas plant," she said. "If a carbon tax/cost is imposed, that's going to impact our members more than other utilities around the U.S. "

Broekema said besides keeping costs low, another primary concern of GRE is helping to meet Minnesota's renewable energy standard of 25 percent by 2020. "We're on pace to meet that," she said. But why biomass? Biomass co-firing represents the opportunity for dispatchable power. Wind and solar do not, so you can't cost effectively manage that with energy demands."

GRE is working on plans to construct a 99-megawatt combined heat and power plant at Spiritwood, N.D., that would produce cellulosic ethanol and a lignin pellet byproduct. For the past two years, GRE has been evaluating available biomass feedstocks within a 50-mile radius of the Spiritwood site to potentially co-fire the plant. "From a broad perspective of what's available, we found not much goes to waste in North Dakota," Broeksema said. "For example, a large potato processing plant and malting plant in the immediate area are already selling their waste streams. "

Co-firing Spiritwood with 10 percent biomass at 99 MW would require about 70,000 tons per year of raw biomass, or 10 tons per hour assuming 5,000 Btus per pound for a continuous operation. If GRE utilized crop residue, about 10,000 acres would be needed to collect it, according to Broekema.

Once a feedstock source is secured, however, operational challenges remain. "There's a level of confidence that says you can co-fire five to ten percent biomass without offering huge operational challenges," Broekema said. "They [biomass crops] are more variable than our coal feedstock we're used to- by season, the soils they're grown in, variations in yearly rain fall and speciation in the crop that you're looking at. For energy grasses, data just isn't available on a widespread basis."

During biomass crop comparison tests, Broekema said in some samples, the alkali and moisture content varied by more than 100 percent. "Biomass has some inherent composition issues that may cause operational problems, and we're concerned about corrosion and emission issues. Alkali can cause slagging of the molten ash in the boilers, causing unplanned power outages, and certain biomass has high silica content and can be erosive in a high velocity boiler situation. We do recognize, though, that there's a tradeoff between low cost, low form value of biomass and higher cost, higher value form."

Alliant Energy's Manager of Biofuels Development Bill Johnson said the driving force in the company's biomass utilization strategy is also to adequately prepare for future carbon regulations. Rather than developing new facilities, Alliant is working to identify existing facilities that are the most compatible with biomass in order to modify or expand their capacity. Alliant currently generates 71 percent of its kilowatt hours from coal at 188 plants across Wisconsin, Iowa and Minnesota, requiring about 17 million tons of coal annually.

Echoing Broekema's sentiments, Johnson pointed out that switching to biomass may not be as easy as it is perceived. "These plants were designed to burn coal," he said, pointing out that a multitude of vastly ranging questions surround biomass co-firing or conversions-from changes in fuel density, size, flow characteristics, durability and supply-opposed to coal's consistency.

Johnson said one of Alliant's plants in Wisconsin has been permitted to test burn feedstocks, and 22 different fuels have been experimented with. "One of the things we've learned is that if we pellet, we minimally touch the product 15 times up to as much as 21 times. If you're not adding value when you touch something you're adding cost, so it became very imperative to us to look at ways to reduce cost to aggregators to reduce fuel costs."

Johnson said Alliant came to the conclusion that if material was densified in the field, the number of times the material was handled could be reduced by 30 to 50 percent, which would drive down cost and allow material to be far more affordable. "We're trying a minimum of a 20 percent co-fire would like to move to 40 to 50," he said. "But first we need to further reduce costs and develop trust with our landowners, producers and foresters in the region."

Adage President Reed Wills and Xcel Energy's Environmental Policy Manager Jim Tunure also presented on the general session panel.