Lukewarm on Cofiring

Cofiring biomass in coal-powered plants is a way to include renewable energy within the existing grid. Can renewable mandates regulations encourage utilities to utilize biomass, and is it a good idea?
By Anduin Kirkbride McElroy
Statewide renewable portfolio standards (RPS), which require that a minimum percentage of electricity be renewable, have been effective in boosting renewable electricity production across the United States. According to the Energy Efficiency and Renewable Energy office of the U.S. DOE, there are currently 24 states plus the District of Columbia that have RPS policies in place, which account for more than half of the nation's electricity sales. Four additional states have nonbinding goals for adoption of renewable energy instead of an RPS.

In most of these states, renewable electricity can be sourced from a combination of solar, wind, hydropower and various forms of biomass. In many states, power companies are allowed to meet renewable standards by cofiring biomass with coal at existing power plants, but it is unclear how many are actually doing so. Cofiring doesn't seem to be a technology that utilities are relying on to meet their RPS, says Carol Stemrich, assistant administrator in the gas and energy division of the Wisconsin Public Service Commission. "[Cofiring biomass is] just one in a mix of options that utilities have in order to meet their RPS," she says. "I think utilities have been concentrating on other technologies more recently and are looking hard at biomass as a stand-alone instead of cofiring." Wisconsin has set an RPS of 10 percent by 2015, and like many other states, allows the renewable portion of the electricity to count toward the producer's RPS.

There are several facilities within the United States that are already cofiring, and some power companies are evaluating the logistics and economics, but it is by no means a widespread practice. As Biomass Magazine has reported, cofiring biomass at coal plants isn't a simple endeavor; boilers must be tailored to handle the physical and chemical characteristics of the biomass fuel, which differ significantly from that of coal. Infrastructure costs and permitting procedures can mean millions of dollars and years of investment before a facility could begin cofiring. In theory, state and federal carbon regulations and renewable mandates may encourage coal plants to begin this process, but so far, it's not clear if a statewide RPS is enough to generate new projects.

North Carolina is one of the most recent states to adopt an RPS, requiring 12.5 percent by 2021. "The expectation is that we will create more demand for biomass materials like urban wood waste, forest thinnings and poultry litter," says John Bonitz, who does farm outreach and policy advocacy for the Southern Alliance for Clean Energy. "Our hope is that we will be building new biopower facilities rather than merely cofiring in coal plants. The thermochemical processes are so much better for the environment."

Concerns about the effects of burning coal have some environmental advocates suggesting that current policies, which allow cofired biomass to qualify as renewable energy, may be misguided. Cofiring is the least desirable option for earning renewable energy credits, says Josh Dickinson, executive director of the Florida Forest Management Trust. He says cofiring should be tied to a net reduction in coal and should be linked to demand-side management, energy efficiency and conservation commitments. Additionally, renewable energy credits should only be permitted for cofiring at coal plants using the best available technology. Though Florida doesn't have an RPS yet, Dickinson confirms that new energy projects in the state are being evaluated-and sometimes denied-because of their environmental impacts.

As it turns out, renewable mandates may mean less to utilities than carbon regulations. As carbon has become an increasing concern, coal plants across the country are feeling the squeeze. Within the past few months, some coal plants in development have been denied various permits, prompting them to abandon their plans.

Despite increasing consumer demand for electricity, some project that concern over carbon will be so great that new coal combustion projects will struggle for approval. David Harlos, principal scientist for Advantek Consulting Inc. in Florida, suggests that the additional costs of biomass cofiring will not help already beleaguered coal combustion projects. "Perhaps most important is the urgent need to not permit any new coal combustion without complete carbon dioxide sequestration," he says. "New coal combustion either locks in the continued emission of fossil carbon dioxide for the life of the facility, or leads to a stranded asset if these new facilities are abandoned before their life cycle endpoints because of later carbon dioxide emissions restrictions. It is this threat, which we suspect has stalled new coal projects in Florida, but it seems unlikely that the addition of biomass cofiring can reverse the economic direction of this new equation. New coal boilers could not economically be fired with replacement biomass, and in most cases biomass cofiring adds capital and operating costs to already endangered projects."

Part of the struggle in permitting comes from convincing skeptics of the environmental friendliness of cofiring. It's not a given that cofiring improves a coal plant's environmental profile, and some critics say the practice is a form of greenwashing-especially if large utilities are allowed to claim it as renewable. Critics suggest that giving coal plants biomass credits subsidizes the plants, incentivizing them to stay open and remain dependent on coal. Other critics say that cofiring isn't the best utilization of biomass. "The problem with cofiring biomass is that if you were burning biomass alone, you could theoretically use the residue or ash as a fertilizer because it has no toxic pollutants in it," Dickinson says. "If you combine biomass with other fuels, such as [municipal solid waste] or coal, the whole residue becomes a pollutant."

Cofire to Clean Coal
One company intends to show that clean coal is possible through emissions control and cofiring biomass. Alliant Energy, a power company that serves Iowa, Minnesota and Wisconsin, has a total generation capacity of 5,894 megawatts. Coal makes up approximately half of that, while biobased sources (anaerobic digesters, biogas and switchgrass) produce just 37.45 megawatts. Alliant performed a 1,700 hour test burn of switchgrass in 2006 at its Ottumwa Generating Station in Marshalltown, Iowa, and generated 17 megawatts from the cofired biomass.

The company is working to permit two cofired plants, according to Manager of Biofuels Development Bill Johnson. In Cassville, Wis., Alliant has proposed a 300 megawatt unit addition, where 10 percent of the fuel will be biomass. The other project is in Marshalltown, where Alliant hopes to build a 640 megawatt facility using 5 percent biomass. Both Iowa and Wisconsin have an RPS.

Johnson tells Biomass Magazine that the state RPS regulations had an impact on the company's business plans, but says "we're ahead of the curve in government expectations." Two drivers are carbon concerns and portfolio diversification. "In order to reduce our impact on the environment and provide a sustainable supply of electricity, we have to look at a wide array of renewables in our portfolio," he says. "Adding to the fleet the capability to burn biofuels in baseload coal plants is an excellent addition and an excellent way to impact the environment. Currently, about 465 megawatts of our portfolio is renewables, and we see the potential to be much higher through the addition of wind and the use of biofuels in our coal plants."

Of course, meeting the energy demand of its customers was one of the greatest incentives for Alliant to develop these projects. "We need new baseload capacity in Wisconsin and Iowa," Johnson says. Alliant sees 3 percent annual growth in energy demand, and that's with aggressive conservation programs. "As much as you can deploy on renewables, there's still a demand on the system," he says. For example, ethanol plants in production or under construction within Alliant's service area demand 350 megawatts, which is more than the Cassville project will produce once upgraded.

Finally, Johnson explains that the old plants needed to be replaced with new emissions technology. "The old plant will be upgraded with new combustion and emission system controls," he says of the project in Cassville. "The old stack will no longer be used, and all emissions will be treated in the new plant and go out the [other] stack. The emission reductions we project from [this project] after we upgrade the old plant (200 megawatts), add an additional 300 megawatts, and burn biofuel at the 10 percent level in the new plant are a 55 percent reduction in nitrogen oxides, 90 percent reduction in sulfur dioxide and 25 percent reduction in mercury from current levels. Therefore, we will achieve these reductions when we are generating 500 megawatts compared with the existing plant at 200 megawatts."

These emissions reductions are why Johnson says the projects have had support from many environmental groups. "You'll find most environmental groups we worked with recognize this is a good direction to go and a good start," he says. "We need to be able to provide technologies to replace older, inefficient and less clean technologies."

Alliant will spend 2008 in permitting hearings and providing testimony. If the company is successful, both plants will be built and ready to produce power in 2013. Johnson says the plants would start burning biomass within months of commissioning, with the goal of reaching the 5 percent and 10 percent levels, respectively, within the first year of operation. To get to that point, Alliant must convince commissions that this is indeed good economics and good for the environment. "I hope people recognize that we are trying to do the right thing," he says. "This will allow us to transition to cleaner plants. A vote for ‘don't do it' is a vote for the status quo, and that's what we're trying to get away from."

Anduin Kirkbride McElroy is a Biomass Magazine staff writer. Reach her at or (701) 738-4962.