How can we balance the need for heat with the smoke it causes? A personal journey.

This essay was reprinted from 
Rural Roots, dedicated to telling 
the stories of rural health in
New England.

By John Ackerly

Growing up in central New Hampshire, my dad taught me how to choose a large round log to place at the back of the fireplace so that there would still be coals in the morning.  He called it an “all nighter log.”  It seemed to work.

I looked up to my dad as a fountain of not just knowledge, but wisdom passed down through the generations. Turns out, some of this was not good advice and was not good for our health.  “All nighter logs” were designed to smolder through the night and open fireplaces are notorious for leaking smoke into the home.  

Early fascination with wood stoves

My dad also made me chop and stack wood far more than I wanted to as I kid.  Once I was old enough to realize how much I loved that activity, I got to experience the challenge of getting my son to do it with me.

I remember a friend once telling me I smelled like wood smoke after I came out of my house.  It didn’t really disturb me at the time, but in retrospect it should have.  As I went through my teens I was drawn to Nichols Hardware, down the hill from where we lived.  In the basement they had dozens of models of wood stoves, and for some reason I just liked being around them. In the late 1970s and 1980s they were so popular the Nichols family could barely keep them in stock. But the idyllic little New England towns, like mine, located in valleys soon became filled with wood smoke.

In my twenties, when I began paying my own utility bills, the benefit of wood heating hit home. Wood is the people’s fuel, and if you don’t want to go out and get it yourself, there is likely someone down the road who sells it.  Its never controlled by some corporate giant that adds any number of taxes and fees to their monthly bills. 

History of wood heat in New England 

After Eva Horton's success in Maine, 
Duncan Symes started Vermont Castings
in the mid-1970s.

In the mid-1800s every house in New England heated with wood and we had clearcut the land for sheep, building and energy.  The Troy New York areas was for woodstoves what Detroit would become for cars.  By 1940, 23% of the country still heated with wood, falling to a low point in 1970 when only 1.3% did. But New England states held on to wood, with 36% of New Hampshire homes heating with it, and 33% coal. 

In 1972, before the Arab Oil embargo, a woman from Maine named Eva Horton was the first American to popularize modern wood stove designs by importing Jotul stoves from Norway.  They used less wood and made less smoke, a dual advantage. Vermont Castings didn’t start until 1975 but soon dominated the market and built a cult-like following.   

Regulation of wood stoves

But the rush for wood stoves in the aftermath of the Arab Oil Embargo led to far too much wood smoke, especially in the Pacific Northwest where trade winds created terrible inversions in valleys, trapping all the wood smoke.  When wood smoke gets that bad, it’s like a nearby wildfire, and the smoke seeps into everyone’s home, regardless of whether you heated with wood or not. 

States put pressure on the EPA to regulate wood stoves and as of 1988, they must meet basic emission regulations.  This helped a lot, as did a declining number of people heating with wood. Today ambient outdoor wood smoke, especially in the Northeast is far better and the biggest health threat is usually not from outdoor ambient smoke, but smoke from your own stove, leaking into your home. 

Choosing a career promoting wood stoves

Nichols Hardware, in lower left, served the Upper Valley
from 1945 to 2006, selling wood stoves and everything
else a country hardware sells.

I moved away from New Hampshire, pursued a career and family, and in my mid-50s, I needed a career shift.  After being an armchair wood stove aficionado, I decided to start a non-profit, the Alliance for Green Heat, dedicated to cleaner and more efficient wood stoves.  With all the interest in renewable energy, I thought there was an opening because wood stoves were in about 10% of American homes, whereas in 2010, not even 1% had solar panels, much less electric cars.  I scraped by earning somewhat of a living for 15 years, finding that foundations, governments and the public regarded wood stoves with some suspicion, even though they are a lifeline to millions of rural households. 

Part of that suspicion is well-founded in that stoves can create unhealthy indoor air, but that does mean all stoves lead to bad indoor air quality.  And the rise of uncertified outdoor wood boilers which create more smoke than heat gave wood heating a bad name during a crucial decade when we were seeking to show wood stoves had promise.  Vermont took the lead to regulate them and then ban them unless they were for homes with virtually no neighbors.

My passion was to computerize the wood stove, and we got grants from New York state and the Department of Energy to hold wood stove design challenges to get manufacturers to add sensors, and combustion fans so people would only have to load the wood, then let modern technology shoot just the right amount of air, at the right time, to the right part of the firebox.

Our group also got funding from the US Forest Service and support firewood banks all over the country, and especially in New England.  The Trump administration is cutting funding for them now, as they are to local food banks.

Environmental and health impacts of wood heat today

Firewood is a very low-carbon heating fuel assuming its harvested sustainably, which is not a problem today in New England. Homes heated with wood or pellets do not contribute to the devastating impact that fossil heating fuels have had.  Wood heating also has a major health benefit because the exercise of chopping and stacking wood is not to be underestimated.

But it also comes with a significant health threat - air pollution -  that many of us like my father, don’t take seriously enough. 

Bottom line: if you regularly smell wood smoke in your home, the safest thing to do is to call a chimney sweep and see if they can help figure out what is going wrong.  Often, it’s from a poorly installed stove that doesn’t have a strong enough draft.  Sometimes, its prevailing wind that blows smoke down your chimney and can be fixed with a special chimney cap.  Or you may be burning unseasoned wood. Whatever you do, don’t ignore it.

Getting to the source of the problem is important but using HEPA air filters can help.  You can even make a low-cost effective air filter from a box fan and a furnace filter. Children and the elderly are most susceptible to poor indoor air quality.

Intergenerational knowledge is extremely important and rural New Englanders tend to understand the importance of securing firewood at least a year in advance and seasoning it well. Burning extra dry wood (15-20% moisture content) in a modern, EPA certified wood stove, and not letting your stove smolder is the best thing you can do to reduce wood smoke for your family and your neighbors.  My dad passed away a few years ago and would laugh if he knew I was writing about his bad advice.  Most of it was good and I will always treasure that.

Low-cost air quality monitors excel at detecting levels of indoor wood smoke

At $39 - $45, real time PM sensors can empower homeowners – and neighbors 

Ever wonder if your wood stove or pellet stove elevates your risk of inhaling particles that could endanger your health?   Recent advances in technology now make indoor air quality monitors small inexpensive and simple for people with wood and pellet stoves - or fireplaces.  The Alliance for Green heat bought and tested several and found the Tempo S1+ Smart Air Quality Monitor is the most versatile, with Govee Smart Air Quality Monitor,  to be a close second.

 

The Govee Air Quality Monitor (right) shows PM, temperature and humidity on a digital display.  The Amazon Smart Quality Monitor on the rleft ($79) only has a small light indicating air quality.

Not all wood and pellet stoves result in poor indoor air quality.  But there is little research that compares different types of wood and pellet stove installations. The human nose is very sensitive and if you smell wood smoke in your home often, that is enough of a reason to look into the problem.  

 

Low-cost sensors like the TemTop S1+, the Govee or the Amazon sensor (that connects to Alexa) detect particulate matter (PM2.5) and can help homeowners better understand the issue and may be a motivating factor to take action, which could mean calling a chimney sweep or just cleaning your pellet stove better before lighting it.  

In the future, such monitors could easily be built into stoves, which could be a significant advance in helping homeowners understand how to best run them.  In 2025, MF Fire plans to introduce an aftermarket sensor package designed to help homeowners operate their stoves better, but they do not measure indoor PM.

Feb. 20. The Govee (left) and Amazon (right) are both easy to set up on your phone and see temperature, humidity, PM and CO on an hourly, daily, weekly or monthly basis. We found they correlated relatively well. They both spiked around 7 PM, cooking dinner but the Amazon did not record much of a morning spike when I lit the stove and cooked breakfast. Both calculated the daily average at exactly 3ug/m3.

On Feb. 19 both the Govee (right) and Amazon (left) monitors caught the morning start-up/breakfast and elevated evening PM.  The Govee had a 2 ug/m3 daily average and the Amazon had a 3 ug/m3 daily average.  One big benefit of the Govee is that is shows temperature on the same screen as PM, and you can see when the pellet stove is turned off around 10PM and turned back on around 6:30 AM. 

 

Digital displays are now everywhere in our homes and cars and they tell us everything from when to add air to our tires to when to change the filter on a furnace.  But for those of us who heat our homes with wood stoves and pellet stoves, the health of our kids and our spouses should be paramount. The EPA also has good information on indoor air monitors.

Another benefit of the Govee is that it pushes a message to your phone, wherever you are, when PM spikes.  At 6:40, just as I was lighting the pellet stove, it briefly spiked to 35 ug/m3, and I got a message on the cellphone when I looked at it, 15 minutes later, at 7:05.  The average on Feb. 21^st was 3 ug/M3.and there was also a little PM elevation around dinner.

 

Low-cost sensors are also useful for neighbors who may be breathing wood smoke from someone else’s wood stove.  When outdoor air quality is bad, it leaks into homes and these sensors can help neighbors talk to each other using data, not emotional reactions, to wood smoke issues.

 

Data from my home’s pellet stove

 

My pellet stove emits a little smoke on start up, but I found that after the first half hour, there is no air quality impact that the sensors could detect. I turn my pellet stove off when we go to bed and when we wake up the sensors usually say the house has 1 µg/m³, meaning 1 microgram per cubic meter of air. By the time the pellets catch fire, it usually reads 6 or 7 ug/m3 but it can also go up to 30 or 40. But if we fry something for dinner, the sensor often goes to 30 or 40, and if we over fry something to the extent you can smell something is nearly burning, the sensor can read 100 or even 200. Our conclusion is that the riskiest behavior in the house is cooking, but your house may be very different, and a wood stove may emit far more indoor smoke than my pellet stove.

 

If I don’t clean the burn pot of my pellet stove, it takes longer for the pellets to light off, and there can be quite a bit of smoke. Currently, I have a Harman Accentra but I had the same problem with a Ravelli.  It appears that the exhaust fan doesn’t go on until the stove sensors fire in the burn pot, but by then the smoke has found any available crack to leak into the room.  This seems like a design flaw, but we all know that positive pressure in a firebox is a recipe for problems.  

 

In our house, we use an older gas stove that is located in the kitchen, about 15 feet away from the PM sensors which were placed just 2 feet away from the pellet stove. Our impression is that regardless of whether you have a gas, electric or induction stove, frying will reduce air quality, particularly at higher temperatures.  We don’t have a exhaust hood or fan above our cook stove, which we presume would be a big help to reduce PM from cooking. A hood with a fan exhausting to the outside may be the best investment in homes that fry food often.

 

Indoor air quality for wood stoves, pellet stoves and fireplaces

Conventional wisdom, based on tens of thousands of wood and pellet stove users, is that indoor smoke is usually far worse with wood stoves.  Part of the problem is that wood stoves need to be reloaded, usually every 1 – 4 hours, and depending on wind conditions outside, how quickly the door is opened, etc. the negative pressure in the firebox is broken, and smoke spills into the room. When a pellet stove is reloaded, you open a door to the hopper, not to the firebox, so there is no impact on pressure in the firebox and no opportunity for smoke leakage. Also, since the exhaust flue is powered by a fan in a much smaller pipe, windy conditions outside are far less likely to impact indoor air quality.

 

An air quality sensor can tell you how bad your indoor air gets when you reload – and crucially – how long it takes to get back to normal. Once you start measuring it, it gives you a metric which can lead to behavior change.

 

With both wood and pellet stoves, improper installation can aggravate or cause leakage of smoke. With pellet stoves, the exhaust pipe has positive pressure and can leak if it's not sealed or installed properly.  With wood stoves, a short exhaust pipe which can often be found in trailers, and self-installed stoves, can lack the suction needed to keep smoke from spilling out into the room.

 

Did I need the sensor to help me understand the relationship between cleaning my firepot better and start-up smoke?  Not necessarily, but it gave me data to measure it on a daily basis, better understanding the solution, and it gave my whole family some reassurance that the stove did not cause much of a problem at all compared to cooking. 

 

How much smoke is acceptable?

It is easy to say that no additional indoor PM is acceptable yet we all live with it when we cook, toast bread and vacuum floors and rugs.  The EPA and the World Health Organization(WHO) say that indoor 24-hour averages should be below 12 – 15 ug/m3, or more recently down to 9 ug/m3. My house, with cooking meals for 3 people and running a pellet stove from 6:30 AM to 10 PM, almost always stayed well under those average limits. However, in homes were a wood stove were to result in daily averages of 20 or more, that would likely be unacceptable to many people, as I think it should be.  Learning when and how to reload your stove quickly and efficiently may help.

 

In terms of outdoor, ambient wood smoke, we know that concentrations of wood stoves in valleys, especially those with more frequent and severe inversions can pose serious health risks.  I have come to believe that restrictions on the new installation of cord wood stoves in those areas is often a step in the right direction.  Wood stoves are not a good energy solution in any densely populated area, not because they are usually not operated well-enough with dry enough fuel. However, we think pellet stoves can be a far greater energy solution than they are today, and should be allowed to be installed even in areas where cord wood stoves aren’t.

 

The toughest question is how to compare and contrast the additional local PM from wood or pellet stoves and the disastrous global impact that oil and gas heating have.  All renewables are increasingly getting local pushback even in the face of overwhelming data showing we need to ramp up renewables far faster than we have been.

 

What do the academic studies say?

There have been multiple academic studies of indoor PM impact of cord wood stoves but we could not find any about pellet stoves. For wood stoves,  one study found an average of 20% higher PM in homes with wood stoves. Another said that wood stoves triple the PM in a homes. Another found that the age of the wood stove was not a determinant of indoor air pollution but more frequent cleaning of the flue was a factor. This was the same conclusion of a well-known study in British Columbia that found there was not a consistent relationship between stove technology and outdoor or indoor concentrations of PM_2.5. Yet another studyfound higher PM in homes with wood stoves and the primary mechanism for introducing PM into the home was opening the door to the stove.

 

Do air purifiers work for wood smoke?

Yes, air purifiers can be effective for indoor smoke from forest fires, your neighbor’s wood stove, or your own wood stove. AGH began promoting the use of air purifiers in 2015 and since then, the rise of wildfire smoke have made them a commonplace solution.  But if the problem is your own wood stove, you should fix the problem before putting a band-aid on the symptom of the problem.  One of the highest rated air purifiers is  Blueair Blue Pure 211i Max(around $279) or Blueair Blue Pure 211+ (around $169).  Both consistently perform nearly as well or better than more expensive ones. One downside for all air purifiers is the cost of replacement filters ($25 - $35 for Blueair filters) which should be replaced once or twice a year depending on how much you use it and how dirty your air is.

 

Purple Air Sensors

I have used multiple Purple Air sensors extensively but did not include any of the data here in part because they are far more complicated to set up and can be glitchy. They are highly recommended, however, for a wide variety of ambient PM measuring. Data from ours led us to the same conclusion: the pellet stove caused a spike in PM when it started, but air quality returned to the same levels as when the stove was off pretty quickly.  With the Purple Air, we also confirmed that by far the worst events in the house were cooking, not starting or operating the pellet stove. 

In 2019, I set up both indoor and outdoor Purple Air sensors at my house, and my neighbors’ who had a cord wood stove. Sensors with a circle around them are indoor. The data was made public, and of interest to the Purple Air community. 

 

Here the Purple Air sensor at the bottom, mostly in green was indoor and the upper one, mostly in yellow was outdoor. Thus, the 7 PM spike from cooking did not impact outdoor PM, but the stove lighting around 8 AM caused a spike indoor and outdoor. (This is data from 2 units but each unit is a combination of two sensors, and you can see how closely they track each other.) 

 

Use of Govee and Amazon sensors outdoors

The Govee and Amazon sensors are indoor sensors but I was curious to see if they could detect start up smoke of my pellet stove when placed on my front porch, about 25 feet and around a corner from my pellet stove exhaust pipe.  I brought both sensors outside and turned my stove off at 11 AM and turned back on at 4 PM.  The result indicates that outdoor emissions of this pellet stove start-up were not detectable at 25 feet away on a relatively windless day

 

This shows that both the Amazon and Govee monitors did not detect elevated PM2.5 during a pellet stove start-up cycle a 4:00 on Feb. 21 when placed about 25 feet from the pellet stove exhaust pipe. If the sensors were placed directly under the exhaust pipe, the results would be very different, as there is always a strong smell of smoke there.

 

Conclusion

We found that our pellet stove does not significantly impact air quality in our home compared to other daily activities such as cooking and cleaning.  The pellet stove does emit some PM on start-up, but on a daily or hourly average basis, it was usually still well within EPA and WHO recommended limits.

 

If you regularly smell wood smoke in your home, you have a problem and you should not delay in trying to fix it.  A low-cost air sensor can be an excellent way to assess the problem with reliable data, or let you know that you don’t really have much of a problem at all compared to other daily household events like cooking and cleaning. 

If you have a pellet stove that emits some smoke on start-up, or if you have done any air quality monitoring in your house with a wood or pellet stove, please contact us and share you experience.

 

 

10 States sue the EPA to improve wood stoves, but the grounds are dubious

Old stoves removed during change out
programs range from ones like these ...

Ten states and one large air agency filed a notice that they intend to sue the EPA over its weak wood stove testing, certification and enforcement programs. The lawsuit is one of the only ways to keep the agency on the required timeline of updating its wood and pellet heater regulations every eight years. Otherwise, the agency can easily let timelines slip and put wood heater policies and regulations on the back burner as both Republican and Democratic administrations have usually done.

The Alliance for Green Heat (AGH) supports the lawsuit for these reasons: EPA needs to keep focused on this technology and keep doing the testing that can get better test methods and stoves that operate better in the hands of the consumer. Automated wood stoves that use sensors, computer chips and actuators to mix the fuel and the air, like in cars, probably offer the best hope for cleaning up wood stoves. But they may be left out of the next updated regulations, known as New Source Performance Standards (NSPS).

... to stoves that are decrepid
and/or dangerously self-installed.

However, AGH does not agree with much of the faulty narrative that says new stoves are not likely to be cleaner than old stoves. And maybe most worrisome is that the AGs of so many states appear willing to make such claims without citing data to support it. 

Unlike the dynamic around auto emissions, where car manufacturers are pitted against the EPA, in this case all fingers are pointed at the EPA for being too lax. The EPA’s wood heater program has had huge weaknesses and it is an easy target. But it is important to understand that the EPA is not a monolith, and it is the wood heater certification and enforcement programs in Washington that are far more of a problem than the section in North Carolina that does the test methods and change out programs.  

One of the many problems with the filing by 10 state Attorney Generals (AG) is that it is mainly based on a review of the EPA’s certification program done by the State of Alaska and Northeast   States for Coordinated Air Use Management (NESCAUM), with funding from New York State Energy Research and Development Authority (NYSERDA). It is not based on testing of new stoves in the field compared to old, uncertified stoves in the field. The narrative that the EPA has been wasting money on change-outs because new stoves aren’t necessarily cleaner than old ones seems to be gaining traction despite evidence to the contrary. Moreover, it distracts from the real, complex tasks at hand and is divisive. As a public relations strategy, it has been successful, gets good media coverage and rallies liberals.

The reality is far more complex. Ironically, it also misses what blue states care about: maximizing renewable energy in smart ways and creating more equity in the energy transition. Starting with the NESCAUM report, pellet appliances have been sidelined from the narrative and they are not even mentioned at a time when much of America is confused about the difference between premium heating pellets and industrial pellets to make electricity. If wood and pellet stoves are to play a role at helping the US reduce residential fossil fuel and protecting low to moderate income (LMI) households from the high costs of the new energy paradigm, it is vital for AG offices to understand the role of the technology in America. 

The Notice to Sue, likely leading to a lawsuit can be good for our common goals of getting cleaner wood stoves, but AG offices need to understand some things. First, we don’t need a new NSPS before we have new test methods. (One of NESCAUM’s many roles is providing data for new test methods, but compared to other labs, NESCAUM’s lab is way behind schedule, which complicates the whole timeline.) Second, the goal of getting better repeatability of a test result within a lab and between labs does not necessarily lead to a cleaner stove in the hands of homeowners. Third, tilting scales toward hybrid stoves may help in the short run, but is not necessarily a long-term or nationwide solution. Fourth, there has never been much agreement on what constitutes the best systems of emission reduction (BSR) in stoves which hinders the EPA in writing regulations that can force technology to change and improve. 

Wood and pellet heaters can help the nation in our transition to electrification by giving homeowners a back-up heating source, lowering stress on the grid during wintertime and providing LMI households protection from rising electricity costs which helps achieve equity. And environmental justice is improved in poor communities not just by a reduction in woodsmoke but also by improving energy security so that homes do not have to choose between heating and eating. For low-income households, change-out programs have been very important by removing unsafe stoves that pose a fire risk, improving not just ambient particulate matter (PM) and indoor PM, and adding heat pumps to many homes. 

The next NSPS will be best served by an EPA with the budget that enables them to collect their own data and properly manage the certification and enforcement programs, which are still far from effective. Underfunding leaves the EPA vulnerable to just reacting to one side or the other, and making poor decisions like revoking a cordwood test method that should have been changed and improved instead. That revocation was also prompted by the same group of states, most of which lack the expertise to understand the complexities and the politics of such a move. Tightening up that test method would have helped the EPA gather vital data it needs for this NSPS and not rely on data from parties who are sparring for an upper hand in the process.

The mostly blue states leading this lawsuit also need to manage wood and pellet heating far better in their own borders, as all states do. Vermont is a good model which is also heavily promoting heat pumps. States should be promoting pellet stoves and boilers and demanding stricter PM limits for those appliances. They should also limit the new installation of cord wood stoves in densely inhabited areas unless, or until, automation and mini-electrostatic precipitators can make cordwood units far cleaner. While cordwood stoves are essential for rural LMI households and help them get off fossil fuels, manually operated wood stoves are simply not a good energy solution where lots of homes are close together, particularly when the topography leads to frequent inversions, trapping PM close the ground where we breathe. 

As for the solution to reduce wood smoke in Fairbanks, even Albert Einstein would be scratching his head. Managers of that change-out program have done an admirable job and used many different strategies. They also uncovered huge problems in the EPA’s stove certification program which were hiding in plain sight. But we should not expect the next NSPS to make much of a dent in that intractable problem. 

Nationally, the solution lies in far more funding for R&D in stove technology, more attention to enforcement of current regulations, more experts for state AGs to rely on and collaboration. Like many big energy issues, the solutions are multi-faceted and rely on a collaborative approach by stakeholders. We should take this lawsuit as a wake-up call.

Recommendations for California's wood stove replacement program

In the fall of 2022, the California Air Resources Board (CARB) published their draft guidelines for their annual wood smoke reduction program. The State legislature committed $5 million for the program that offers financial incentives for homeowners to replace older, high-polluting wood burning devices with newer, cleaner burning units.  The Alliance for Green Heat submitted the following comments, urging California to 1. focus first on households in more densely populated areas where the public health ramifications are the highest, 2. to consider the benefits of hybrid stoves over catalytic stoves and to expand the number of eligible non-cat stoves, 3. to make sure California fully integrates wood stoves into its energy audit and weatherization programs, which would lead to more voluntary stove removals and repairs, 4. and to study and better understand the actual carbon footprint of firewood based on estimates of how people source their wood.

Dec. 8, 2022 

Hon. Steven Cliff, 

Executive Officer

Channel Fletcher, 

Deputy Executive Officer, Environmental Justice

California Air Resources Board

1001 I St,

Sacramento, CA 95814

 

Dear Mr. Cliff and Ms. Fletcher,

Thank you for the opportunity to provide comments on your draft Program Guidelines to reduce wood smoke. Funds to replace older stoves with cleaner sources heat are funds well-spent, especially since many old stoves provide primary heat to homes of marginalized, lower-income households.  

1.      Focus on households in densely populated areas

Our biggest recommendation is to focus your resources on households in areas that are more densely populated and/or experience frequent weather inversions, where the public health ramifications of older wood stoves are the highest.  Stoves in very rural homes with few or no neighbors will have very few public health impacts. This is an area that more change-out programs should explore.  Hopefully, homes in these sensitive areas would opt for heat pumps or pellet stoves. For homes in densely populated areas, we would also encourage you to see if the home has a woodshed or a way to store their fuel.  

2.     Replacement devices

We fully support CARB’s decision to replace older wood stoves with low-carbon alternatives such as heat pumps and pellet stoves.  We would be wary to include electric resistance stove heaters because this may burden lower income homes with higher electric bills than they can afford, assuming electric rates rise in the future.  We are glad that CARB does not include gas stoves as that would have a counterproductive carbon impact and hinder electrification goals.

We do not have a high level of confidence in catalytic stoves as they often are not maintained or used properly as the years go by, especially in lower income homes who may not be able to pay to replace the catalyst when needed.  Hybrid stoves are a far better option, and we would urge CARB to focus on hybrid stoves because they still provide valuable PM reduction technology even if the cat is not engaged.  It is important to understand how stoves are likely to work in the real world, once they leave the lab, and cat stoves are a class of stoves that can work even worse than non-cats if they are not maintained or used properly, particularly after the home or stove is sold and the device is being operated by a new owner.  Some owners of older cat stove do not even know they have a cat stove.

We are extremely concerned that CARB is only making four models of non-cats eligible for change-outs. The four non-cats selected by CARB may operate better than some with greater testing flaws, but there is no proof that many non-cat stoves are just as good as the four you identify.  The process undertaken by the Alaska and NESCAUM was valuable in many ways, but it does not easily lend itself to being used to qualify stoves for change-out programs.  If CARB wants to identify non-cat stoves that would burn more cleanly, allowing more single burn rate stoves to qualify may be the best way.  However, most households do not want single-burn rate stoves, particularly if the stove is their primary heat source.  

A major dilemma for your program is that you are trying to serve many marginalized, lower income households and balance their legitimate energy needs with the impact their smoke will have on neighbors.  By choosing only 4 non-cats, you are sidelining the heating needs of these households in favor of a very questionable process to identify only 4 models, some of which are not likely to be available near these homes.

We support the effort undertaken by Alaska and NESCAUM but decisions like this, to select four stoves, takes their data beyond its usefulness. We think there is disconnect between limiting to 4 non-cats and serving low-income households.  Though we understand the desire to put Alaska’s work to use, it will likely be ineffectual in reducing PM in this change-out program. 

3.     Inspection, repair and safety

One of the best ways to start to identify, repair and/or remove old stoves is to ensure that local energy audits and weatherization programs have integrated wood stoves into their work.  Most energy auditors still do not have the training or the software to do undertake stove inspections, even though DOE and state regulations claim to require that all heaters are inspected.  If they did, they would find many self-installed stoves that are dangerous, higher polluting and in need of replacement or removal.  LIHEAP funding and low-income weatherization programs will cover these costs where the stove is the primary heat source.  If the stove is a secondary heater, these programs could cover repairs.  Few states have demanded that the US Department of Energy develop standards for inspecting wood stoves, like there are for boilers and furnaces, and the DOE is still hesitant to take this on, even though it would have a major impact for lower-income households across the country.  We urge CARB to review how wood stoves are inspected during energy audits and weatherization programs in California and see whether they are being repaired, replaced or removed.

4.     GHG reductions 

We are pleased that CARB is no longer using carbon to justify switching from a wood stove to a gas stove.  In its 2016-2017 Woodsmoke Reduction Program Guidelines, CARB stated, ”Switching from an uncertified wood stove to a natural gas or electric heating device reduces GHG emissions.”  We find this statement to be without scientific basis.  We understand that the GHG calculations are not central to how CARB runs this change-out program, but we want to open a conversation about it.  

In the current Program Guidelines, CARB seems to assert that 100% of carbon released from wood and pellets should be attributed to this form of heating.  The Guidelines say that “biogenic CO2 is included in the calculation of GHG benefits for these devices.”  We agree that some biogenic carbon should be included, as some carbon can be attributed to all energy sources.

To make scientific estimates of carbon released from firewood that would not have been released anyway, there is a lot of data that can be considered.  For CARB to start to gain a basic understanding of the carbon cycles from firewood, you could also ask on your change-out application, “where do you get your wood?”.  A researcher can also get data from a sampling of California firewood dealers and households who use firewood. 

By not engaging in basic research, CARB is putting the burden on low-income households who heat with wood and is inferring their carbon impact of their heating is far higher than it is. This flies in the face of current thinking about energy justice that seeks to remediate social, economic, and health burdens on those disproportionately harmed by the energy system. 

Estimating carbon from gas, oil and electricity involves a complex set of assumptions and calculations and there is no reason that similar effort could be made to assess the carbon cycle from firewood.

In California, as in the rest of the country, it is likely that a substantial number of homes who heat with wood acquire their firewood in a very responsible way by using dead and downed wood, as lower-income households do around the rest of the country.  A lot of firewood used for home heating could otherwise end up in the landfill where it would produce worse GHG emissions.  

The Minnesota Residential Wood Combustion Survey Results, (May 2019) done by the Minnesota Department of Natural Resources is one of the most definitive studies on firewood procurement and use.  The report says, “Most of the wood cut (84%) by residential households comes from dead or downed trees, land clearing, and logging residues (Table 15). Approximately 9.3% comes from live standing trees in the forest.”  This is a crucial statistic for understanding carbon impacts of firewood.  If 84% of wood cut by households comes from dead of downed trees, it means that carbon was already in the process of being released unlike when a live tree is cut.  

Household income generally correlates to how firewood is procured and how much firewood is used.  The lower the income of a household, the more wood they use and the more likely they gather their own wood, assuming wood is being used for heating, and not for recreation.  More urban and higher income families are more likely to purchase wood. The chart below is based on EIA data.

The Minnesota Residential Wood Combustion Survey Results, found that 60% of firewood is cut by households and 40% is purchased.

 

Table 15, below, provides further detail of where firewood comes from in Minnesota, and these trends are likely to exist in other states. 

Table 17 shows a breakdown of firewood from both household and loggers.  Even where firewood is provided by commercial loggers, most of it is still from trees that are dead, down or from the residues of a commercial harvest, which usually is for sawlogs (lumber).

In conclusion, we believe that whether firewood comes from a “locally or nationally approved” forestry plan is not as relevant as existing data about where firewood comes, how sustainable it is and how to understand carbon implications. From a carbon perspective, we believe a rigorous look at the carbon footprint across the value chain of gas production and usage will always be higher than the footprint of firewood, across its value chain. The Achilles heel of firewood is the excessive PM that comes from most wood stoves, and it is that PM which fully justifies change out programs like this one.

As we initially stated, we fully support this program and see it is improving over the years, and we hope that our comments help improve it in future years.  Thank you for undertaking the program and accepting comments from the public. 

Sincerely, 

John Ackerly

President

Further reading: State Parks give downed trees to public for firewood (March 2023)

Trump Administration to change Obama era wood stove and boiler emission regulations

Delaying or weakening emission regulations will impact thousands of communities nationwide

The EPA is “taking steps to provide relief to wood heater manufacturers and retailers” according to a statement released by the EPA.  The EPA expects to issue a proposed rule this spring that could potentially weaken parts of the regulations enacted under the Obama administration.

January 2019 update: The EPA has proposed giving a 2-year sell through for wood boilers and furnaces, allowing manufacturers to make and sell Step 1 units right up until May 2020.  Those units could then be sold through May 2022 by manufacturers directly or by retailers. Attorney Generals from seven states filed comments saying the EPA did not have the legal authority to provide such sell-throughs, portending a legal fight.

March 2020 update: The EPA issued its final rule and decided not to provide any sell-through periods for any class of wood heater.

The April 2018 move to provide relief is supported  by companies such as Central Boiler, the largest outdoor wood boiler manufacturer in North America, who has been aggressively lobbying to delay and weaken the standards that were to come into effect in 2020. But to some smaller companies who have already invested in the R&D to meet the stricter 2020 standards, the EPA announcement undermines the significant investment they’ve made in designing cleaner and more efficient wood heaters. 

Thousands of cities, towns and communities are impacted by excessive wintertime levels of wood smoke, posing health risks and undermining support for an iconic renewable energy technology.

It is widely expected that part of the relief that EPA will be providing to industry is a three-year delay in the emission standards that were  set to take effect in June 2020.  Republicans in the House of Representatives had already passed legislation for a three-year delay, but the Senate has not.  A court filingby the EPA said that it “intends to take final action on this first proposed rule by this fall,” and that would allow manufacturers to slow down their R&D and certification testing.

But the EPA can pick and choose which parts of the Obama era wood heater regulations that it wants to rewrite and they say they will issue a series of federal register notices asking stakeholders for comment and input on substantive issues.  Experts believe that a statement released by the EPA indicate that emission test methods are being considered. 

Environmental groups, industry and the EPA have been wanting to move away from testing and certifying wood stoves with crib wood – 2x4s and 4x4s – which has been the standard testing fuel since the first set of wood stove regulations in 1988.  All parties want to switch to using cordwood, the fuel used by homeowners, recognizing that stoves have been fine tuned to run better on crib wood, rather than cordwood.  This has resulted in stoves that may run at 4 grams an hour of smoke in the lab, but may be 10 grams an hour or more in the hands of homeowners. In a statement this week, the EPA said it is concerned that its regulation“may not be achieving the environmental benefits it was supposed to provide.”  

The EPA appears likely to accelerate the transition to testing with cordwood but industry seems to favor an ASTM cordwood test method while some states and others are developing a new method that reflects how stoves are used by homeowners.  This method, call the Integrated Duty Cycle (IDC) method is still in draft form and is a drastic departure from the traditional way that stoves have been tested since the 1988.  

The EPA could also decide to weaken emission limits for wood boilers, which would primarily benefit the outdoor wood boiler industry led by Central Boiler.  

Since the 2015 regulations went into effect, scores of wood and pellet stoves and boilers have been tested to meet the 2020 standards and most prices have not gone up significantly.  The 2015 regulations began a process of requiring that manufacturers test and report their efficiencies, and delaying the 2020 deadline would set back efficiency disclosures, harming the ability of consumers to choose more efficient appliances. 

States are allowed to set stricter standards but not looser ones, and if the EPA were to weaken the federal rule too much, some states could either stick to the original standards set by the Obama administration in 2015 or develop new ones. States like New York, Oregon, Vermont and Washington are already battling long-term wood smoke problems and have started to chart their own course for wood heater regulations. If several states adopted a different cordwood test method or stricter emission standards, they could have a “California effect” of moving the entire market.

“We are very concerned that the Trump Administration  may weaken consumer and environmental protections for wood stoves,” said John Ackerly, President of the Alliance for Green Heat, an independent non-profit that promotes cleaner and more efficient residential wood heating. “Wood and pellet stoves are vital to help families affordably reduce fossil heating fuels, but we can’t move this technology forward unless they can burn cleaner in people’s homes,” he said. 

March 11, 2020 update: The EPA finalized amendments to the 2015 NSPS and did not provide a retailer sell-through or any extensions for central heaters or room heaters.  They did remove pellet fuel minimum requirements but retained the list of prohibited fuels in the 2015 NSPS.