Lots of Maine residents rely on wood stoves as a primary or secondary home heating source. The design of today’s new stoves differs dramatically from those made during the heyday of “airtight” stoves back in the 1970s. Innovations in making stoves more efficient and cleaner — producing fewer particulate emissions, or smoke — were driven by Environmental Protection Agency (EPA) regulations. Those rules are in the process of changing again, which should make for even cleaner air. It will also likely mean more expensive stoves, according to retailers.
“There was nothing airtight about the old ‘airtight’ stoves,” said Jim Rockett, a salesman at Evergreen Home and Hearth in Ellsworth. As a marketing focus, he says, “airtight” was meant to suggest that customers would to be able to shut the stove down by eliminating the air, go away for the weekend, and have the coals there when they got home two days later.
“But in an oxygen-starved environment, you’re creating huge gobs of particulates,” Rockett said. “In Maine, we don’t have a lot of mountain valleys, so we don’t suffer from inversions. Here, the dirtiness of the stove really manifested itself in chimney fires. Every morning in the winter I hear of one on the news. They’re dangerous, and horrible things happen, and if you just had a decent stove it wouldn’t happen.”
In 1988, regulations went into effect capping particulates from these stoves at 7.5 grams per hour.
“That was a nearly 90 percent reduction in most cases,” Rockett explained. “Because depending on the size of the stove, they were emitting between 75 and 100 grams of particulates every hour.”
The changes were driven by health concerns. The EPA is required by the Clean Air Act to set new performance standards for stationary sources of air pollution that may endanger public health or welfare.
“Wood smoke is made up of a mixture of gases and fine particles that are produced when wood and other organic matter burns,” according to EPA materials. “The particles in smoke — also called particle pollution or PM — can get deep into the lungs, harming the lungs, blood vessels and heart. People with heart, vascular or lung disease, older adults and children are the most at risk.”
Rockett says he lives in an Orono neighborhood with small ranch houses and lots of wood stoves. There also are lots of folks out running in the morning, and he worries about air quality especially for them, since many of the houses don’t have clean-burning stoves.
“When I back out of my driveway in the morning in the winter, I always look up at my chimney and I smile if all I see are heat waves, no smoke,” he related. “There are particulates in there that you can’t see with your naked eye, but there’s a lot less.”
The 1988 rule change was a shock to the wood stove manufacturing industry.
“In one year, it went from about 600 manufacturers of woodstoves down to about 30,” Rockett said. “Those were the only ones that could afford to comply. Now it’s gone up to about 45.”
The world’s biggest wood stove manufacturer, Jotul (pronounced yo-tul), recently opened a plant in Gorham to house all of its North American production activities.
What the Norwegian manufacturer designed with to make its stoves compliant, Rockett said, was elegant, but it took lots of prototyping. He contrasted the process with what happened when EPA began to require low-volume toilets.
“What the EPA did was, they said you have to get to 1.5 gallons and this is exactly how you’re going to do it,” he recalled. “Those toilets didn’t work. They were so bad that the 5-gallon ones were being sold on black markets. What EPA did with wood stove manufacturers is say you have to go from 100 grams to 7.5, but we don’t care how. They left invention and ingenuity out there and they came up with some pretty bright ideas.”
The bright idea was a secondary combustion system whereby the stove burns stored smoke before it goes up the chimney. The smoke is unburnt fuel, so any of it that leaves the system will end up either in the chimney as creosote or in the air and our lungs, causing adverse health effects.
“These stoves guys have gone from 40 percent efficient to 75 percent efficient simply by burning all the fuel, the smoke, before it goes up the chimney,” Rockett said. “If you look in the stove, there’s a hollow baffle and it’s attached to a manifold in the back.
“When that manifold and baffle fill up with air, the chimney is going to pull the air out of these little holes, but because the volume here is so big and the holes are so small, the air stays inside that manifold for a pretty long time. It’s kinda like the Jersey Turnpike with only one tollbooth open.
“So the air inside that manifold will get up to as high as 1,700 degrees F. By the time the air gets pulled out of those holes and comes into contact with the smoke, it’s hot enough and oxygen-rich enough that it ignites the smoke before it goes up the chimney.”
The emission limit of 7.5 grams changed again this year. Last February, the EPA announced that they would reduce the maximum allowed emissions further, to 4 grams per hour. The rule took effect in May, 60 days after the March 16 publication date of the new rule in the Federal Register. Like the old rule, it only applies to new stove manufacturers. Old stoves can still be legally used, and re-sold.
All the stoves in the showroom at Evergreen this fall will meet that new standard, Rockett said.
“That part is not controversial,” he said.
Their concern is about the second phase of the new regulation, set to go into effect at the end of 2018. It’s a further step down from 4 grams per hour to 2 grams per hour, he said.
At that level, stoves must have not only the secondary combustion system but also what’s called a catalytic combuster. It’s a small honeycomb-shaped piece in the stove coated with platinum or palladium that acts as a catalyst to burn any remaining smoke that doesn’t get burned in the baffle or air tubes.
“That’s going to increase the cost of the average stove about $700 because of the technology required,” Rockett said. “It’s a tiny improvement at a huge cost.”
There are no government trade-in programs to encourage Mainers to upgrade their old, noncompliant wood stoves. In some places, however, the American Lung Association has created “changeout” programs funded by fines paid by companies found to be in violation of the Clean Air Act.
So far, according to Michelle Edwards of the American Lung Association of the Northeast, the only such program in Maine is in the Rumford River Valley. In other cases, she said, companies voluntarily create clean air implementation plans that can include funding replacement programs.
“The Lung Association is thrilled to have this first program in Maine,” Edwards said. “We’re hopeful that other companies will see the success and voluntarily put some money toward a program.”