Daily Archives :

Monday, March 31, 2014

On Board with Energy Crops

300 140 Miguel Ángel Martínez

Near the Columbia River just outside of eastern Oregon’s Boardman sits the state’s last operating coal plant, a 600-MW facility built in the late 1970s. Though the plant has plenty of years left in it, the state’s decision to phase out coal left Portland General Electric exploring its options.

In 2010, PGE was approved to continue to burn coal at Boardman until 2020, with some temporary emissions controls upgrades. After that, $500 million in additional pollution controls would be required to comply with federal and state sulfur, nitrogen and mercury rules, thus enabling the plant to continue operations until at least 2040.

Ultimately, PGE faced three possibilities—closing by 2020, making costly upgrades, or switching to another fuel source. If closed, it would make history as the youngest coal plant in the U.S. to shut down as a result of air quality regulations, but doing so and building a new plant elsewhere makes more economic sense than keeping it open for upgrades.

With the upgrade option ruled out, the fate of the plant rests on the feasibility of using torrefied energy crops as fuel, and PGE has spent the past several years conducting in-depth research and rigorous testing to determine what the possibilities are.

Exploring Options

Initially, PGE looked into repowering with natural gas, but rendered that option unfeasible. “We did a study on natural gas and found the area didn’t have a gas line, but that wasn’t the real issue,” says Jaisen Mody, PGE projects manager. “The issue was that the Boardman boiler was designed for coal combustion, and using gas in the existing boiler made it highly inefficient. The cost wasn’t conducive to running the plant long-term, as we would have to change out the boiler. We decided that converting an old Rankine cycle coal boiler wasn’t the way to go because of the capital expenditure.”

Basically, it boiled down to the notion of using gas meant building a new gas plant, adds Steve Corson, PGE spokesman.

When PGE began evaluating biomass back in 2010, wood pellets were tested but gummed up the plant’s pulverizers. Crop research began at that point, and arundo donax was chosen as a fuel of interest due to its great growth potential. It’s been found to produce upwards of 35 dry tons per acre per year, compared to switchgrass, which will yield 4 to 13 dry tons per acre per year.

PGE has been growing arundo test plots around the Boardman area for the past couple of years—about 92 acres—and has harvested it a few times, storing the crop for test burns, Mody says. He adds that while the initial emphasis was mostly on arundo, that’s changed a bit.

On one hand, a single energy crop is attractive because it’s dedicated to producing feedstock volumes needed, but reliance on a single fuel source is risky for a number of reasons, including harsh weather, natural disasters or pests. “So we’re also investigating other biomass sources, including sorghum and ag waste,” says Mody.

One thing that’s certain is that if energy crops and biomass are used at Boardman, they will be torrefied first. “Torrefaction is the right way to repower Boardman with biomass, because we’re anticipating no changes to plant equipment,” Mody says.

Corson adds that torrefaction would allow the plant to pulverize the fuel just as it is doing with coal, but green biomass would require a lot of changes. Additionally, researchers have found that torrefied biomass is more hydrophobic than Powder River Basin coal, which is currently used at Boardman.

Later this year, PGE is installing a torrefier at Boardman, and will then begin its test burns, according to Mody. “These test burns are critical for us,” he says. “We think running this test will prove to us that we can run torrefied biomass through the plant, and we’ll also collect emissions data. Then we’ll sit down and figure out what it’ll take to run the plant for air permitting and the economics of that.”

Mody notes that each feedstock tested—arundo or sorghum—could have a different effect on the boiler, slagging or fouling it, so close attention will be paid as to what source is torrefied and how.

According to a study done in 2012 by researchers at the University of Washington, Washington State and Oregon State University, operating at 300 MW and producing power under optimal economic conditions, about 1.25 million tons of torrefied arundo would be used by Boardman, based on the Btu content of torrefied arundo (10,400 Btu per pound). About 94 dry tons of arundo would produce 52.7 tons of torrefied chips, the researchers found, so a total of 67.6 thousand acres of arundo would be required to produce 1.25 million tons of torrefied chips and support torrefaction, assuming 33 dry tons per acre per year.

Of course, while multiple sources would be used, Mody admits obtaining necessary quantities remains PGE’s biggest challenge in the quest to repower with biomass.

Moving Foward

“It’s [repowering] always been one issue—the source of biomass,” says Mody. “How can we procure and move enough in an economic manner that would sustain a large plant? The production of biomass, whether we’re growing or buying it, remains our biggest challenge. That’s why we’re looking at diversity now—one species isn’t the answer. It’s about what we can grow at a reasonable price, and what’s available out there.”

If the torrefaction test burns are successful, more work has to be done to calculate the economics and emissions profiles of a full-scale torrefier. Once that data is complete, PGE will bring it to its integrated resource planning process, which is a comprehensive plan presented to the public utility commission that lays out its generating portfolio resource requirements.

At that time, the next step for Boardman will be decided, Corson adds. “At this point, what we’ll really be saying is, okay, we know we can do this, is it better than the other options?”

Global pellet market to reach $9 billion by 2020

300 200 Miguel Ángel Martínez

The global market for pellets is expected to double in the next seven years, growing from a $4 billion market to $9 billion, Michele Rebiere with Viridis Energy Inc. told attendees at the Pellet Supply Chain Summit, March 24. The summit preceded the International Biomass Conference being held March 24-27 in Orlando, Fla.

Speaking in the closing panel of the day, Rebiere said the largest market, by far, is the European, with 20 million metrics tons (mmt) used in 2013 for both industrial power and residential heat. That is forecast to grow to 28 mmt by 2015 and 42 mmt by 2020. The North American market, is now at 4 mmt and forecast to be 5 mmt in 2015, but she added, are understated going out further. “I think the forecast in North American will increase substantially,” she said added, as the interest in cofiring with coal is likely to increase which the forecasts won’t include until projects are announced. The Asian market is expect to grow as well, from 1 mmt in 2013, to 3 mmt in 2015 and potentially 7 mmt by 2020. While the power market is the largest market contributor, the heating market is growing rapidly. Italy, in particular, garnered attention with the doubling of its demand in one year.

Seth Ginther, executive director of the U.S. Industrial Pellet Association, was a bit more conservative on his growth projections, pointing out that 2020 estimates range between 25 mmt and 70 mmt. “I think that 2013 was the year we’re beginning to see where the market is going to shake out. It’s going to be more like the 25 mmt level, but that still is going to be significant.”

In his discussion on the changes in the United Kingdom’s incentives, Ginther said it is important to note that the incentives for biomass conversions are aimed at helping develop infrastructure. And, as the carrot is phased out, the stick – the price of carbon – is being increased, making it very expensive to burn coal. As a result, UK power producers are expected to continue to move towards biomass.

As a large UK buyer of North American pellets, Richard Peberdy, vice president of sustainability for Drax Biomass International, outlined his company’s commitment to biomass power and its interest in sustainability. The UK power producer has experimented with a number of biomass sources to supplement coal since 2008, making a commitment to pellets to provide a large portion of its biomass needs. It has two pellet facilities under construction in Mississippi and Louisiana and is building a port facility in Baton Rouge, La.

The first of three boiler conversions has been completed at Drax, with the second to be brought into service later this year and the third planned for 2015. Peberdy reported that Drax was pleased with the performance of its first biomass boiler conversion at the end of the first year of operations. “It’s outperformed our expectations in the first year at 39 to 40 percent efficiency on 100 percent biomass.” That is significant, he added, because UK sustainability reports projected biomass power would only reach 25 percent efficiencies, much lower than coal power’s average 35 percent efficiency.

Peberdy described Drax’s commitment to sustainability, pointing out that the company established its own sustainability goals even prior to the development of UK standards. The pressure for sustainability brings benefits, he said, by increasing investments in forests, in outreach to forest owners and in safer and better systems for making, handling and moving pellets.

Ben Conte, renewable energy sales manager for Bridgewell Renewables, filled out the panel at the summit on market energies by describing the work his company has done in marketing pellets in the EU. Much of the Bridgewell’s focus has been on meeting the high quality heating market, working to help its customers with their branding efforts. While Bridgewell is developing a brand to be able to meet spot markets, much of the work it’s done has been in seasonal 3-6 month contracts as well as long term contracts for one or two years. “The market is evolving,” he said. “The industrial and residential markets are linked in Europe and Asia,” he added, and are getting more sophisticated.

Other panels during the day included industry speakers addressing forestry ownership implications, sustainable forest management, pellet mill design considerations and infrastructure.


Uso de cookies

Este sitio web utiliza cookies para que usted tenga la mejor experiencia de usuario. Si continúa navegando está dando su consentimiento para la aceptación de las mencionadas cookies y la aceptación de nuestra política de cookies, pinche el enlace para mayor información.plugin cookies

Aviso de cookies