Diving into Wood Heat

Wood waste is the heating fuel of choice at the Bismarck State College Aquatic and Wellness Center.
By Katie Fletcher | September 16, 2015

In the winter, if the breeze is just right, you may smell a hint of a campfire entering or leaving the Bismarck State College Aquatic and Wellness Center located in Bismarck, North Dakota. Operations Superintendent Ryan Geerdes says, although it may be over simplifying, “When you break it down, it’s just a big bonfire that is computer controlled.”

In 2010, when the facility was built, the decision was made to generate heat using wood waste sourced from the Bismarck Municipal Landfill. After working with the fuel over the past few years, Geerdes and others have devised an effective way to heat the facility, pool and domestic water at a fraction of the cost to other fuel sources. Although they didn’t start where they are today, the facility’s King Coal boiler now runs at about 85 to 90 percent efficiency in the winter.

The boiler adds to the list of reasons to visit the facility. Kevin Klipfel, facilities and program director with the Bismarck Parks and Recreation District, highlights the system’s teaching-tool nature. “The local college has brought classes over to look at the system and to educate the kids on what is involved,” he says. The approximate 66,000-square-foot BSC Aquatic and Wellness Center is located on the college campus. The building houses a 50-meter competition pool, diving, recreation and lap pools, and the wellness center includes strength and cardiovascular equipment. The center also has a playground, a group fitness and dance studio and meeting rooms. A variety of people utilize the facility, and it hosts a number of events—from high school state swim meets to the Paralympic Pan Am games this December. Whether it’s a therapy session in the warm rec pool or a hot shower after weightlifting, the combustion of wood waste makes them possible.

Big Learning Curve
The idea to install a biomass heating system at the BSC facility all stemmed from personnel learning about a smaller-scale biomass unit the Bismarck landfill was using to heat its shop in the winter months. Phase one of the project was a feasibility study. Randy Bina, executive director of the Bismarck Parks and Recreation District, says the study, which was part of a grant application and overall justification for the system, yielded positive results. “It showed that there would be substantial savings on heating costs for the facility,” Bina says.

Grant funding from the North Dakota Forest Service Fuel for Schools Program was received to assist with the purchase of the boiler technology and some of the wood waste handling equipment, including a payloader and trailer to haul the wood waste to the center.

Similar to the unit at the landfill, a locally manufactured King Coal boiler was installed, with a larger output of approximately 10 million Btu to heat the facility using hot water. When the center opened its doors in March 2010, it initially ran on natural gas. After a few months, all of the equipment was in place for the biomass system, and it was fired up.

Geerdes takes care of anything mechanically related at the center, including the role of caretaker of the biomass boiler. When Geerdes was hired a few months prior to the grand opening, he was green to this green technology. “I was there for all of the startups, and when we got ready to run the biomass I was about as green as you can get,” Geerdes chuckled. “I think it was a big eye-opener for King Coal, too, because they weren’t used to doing systems that don’t have a consistent fuel source that is screened—to go to whatever you are getting from the landfill, which could be seatbelts and whatever else the guys run through the grinder. It was a big learning curve for everyone.”

It took about a year to get the right combination of fuel to make the system run optimally. The system began fueling with dirtier wood waste from the landfill. “After the first couple of years we got better—as we had better fuel, we had less problems,” Klipfel says.

“We were babysitting it day and night, and that’s when we finally just said that this is ridiculous, we have to change some stuff,” Geerdes says. Those involved with running the boiler met with the landfill staff and discussed options with the wood waste. Now, the feedstock is composed of dried, large logs and wooden pallets. According to Geerdes, the landfill staff takes special care to ensure the wood chip pile is clean and on-spec, now that the demands of the biomass boiler are better understood. “King Coal changed some equipment to handle what we’re getting and meeting with the landfill helped everything,” Geerdes added.

Nuts and Bolts
The pile of wood chips at the landfill is loaded onto a trailer that can hold about 4.5 tons of product. In a year, Geerdes says they make about 130 truckloads to and from the facility—a 45-minute round trip—which works out to be about four loads a week in the summer and four loads every other day in winter. Between 1,200 and 1,500 tons of wood waste are sourced from the landfill per year. The center has onsite fuel storage capacity of 40 tons, or about four or five days’ worth.

During the winter, the boiler burns about 7 to 8 tons per day, and in the summer, about 1 ton per day. The system running at its max can burn 30 pounds per minute. Prior to combustion, feedstock is moved from the storage bin onto a vibrating table where it is sized down to 2 or 3 inches. A 25-pound magnet at the end collects all of the metal, such as nails from the pallets in the wood waste mix. Approximately 5 gallons of metal and nails are removed per day. Any oversized biomass and metal is recycled back to the landfill, and ash is augured into a dumpster and brought back to the landfill to use for cover. Prior to changing the mix of fuel, the biomass system was producing three to four times the amount of ash it does now, wearing the equipment down. Today, however, the system averages 3 to 5 percent in ash waste. The remaining ash—within EPA standards––is removed from exhaust gasses before it goes out the stack.

The boiler is made to burn the biomass as efficiently as possible, with the stoker temperature kept between 1,000 and 2,000 degrees Fahrenheit. “We have a couple fans, one blows underneath to stoke the fire and another blows around the top of the fire,” Geerdes says. “We burn everything—all of the combustible gases—so we get as much heat out of the wood as we possibly can.”

The fuel is raked a few times a day, depending on how much wood is burned. In the stoker box, Klipfel compares the movement of the fuel to a volcano. The fuel gets pushed up into the bin from the bottom like a volcano, although, not to that magnitude, he says. “It gets pushed up slowly and as it burns, it spreads out,” Klipfel says. “You try to rake the material back to the middle to get it to burn hotter.”

The material is raked using equipment similar to a hoe. Raking is also done to get rid of what the staff refers to as clinkers—chunks of dirt and sand that have melted together—that sometimes form in the combustion process. The system runs year round, 24/7, unless down for maintenance. “We can usually go six, seven months with nothing happening and then a bearing might go out or something like that, but usually if we can run all year long we will,” Geerdes says.

The system helps save dollars while utilizing a source of fuel that would have otherwise been wasted. “We continue to see financial savings by using this system,” Bina says. “In addition to that, it’s a way of reducing that waste at the landfill.”

Besides a workout, visitors can add a look at the biomass boiler to the reasons to come to the facility. Some even don’t mind bypassing the swimming pool and consider the biomass heating system the main attraction. “A lot of people will come up on tours and say let’s get to the fun stuff,” Geerdes says. “Everyone thinks it’s neat.”

Author: Katie Fletcher
Associate Editor, Biomass Magazine
[email protected]