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)

Massachusetts renews innovative stove change-out program

Changing face of wood stoves in America includes a comeback of catalytic stoves 

Massachusetts announced an 8th round of annual funding for its innovative wood stove change out program. The program was the first in the country to develop a change out program that gave higher incentives to fully automated stoves and stoves that provide a verified efficiency on the list of EPA certified stoves.  The program has since been discontinued but may come back again.

The program, updated in April 2019, changes some of the rebate levels and provides consistently higher levels of rebates than most change out programs. It now offers Massachusetts residents between $500 and $3,250 for upgrades, depending on the stove and income level of the family.  To be eligible, households must have an operating, uncertified wood stove to trade in for a new wood or pellet stove.  Rebates can cover 30 - 80% of costs of the new stove and installation.

Governor Charlie Baker said in a statement the change-out program "improves air quality across the commonwealth and helps residents save money by adopting more efficient, cost cutting heating technologies."

The program favors appliances that burn more cleanly in the hands of consumers by offering the highest rebates ($1,750) to pellet and fully automated stoves that have listed efficiencies over 65%. The highest wood stove rebates ($1,250) can be claimed for catalytic (or hybrid) or non-catalytic stoves that emit 2 grams an hour or less and have a listed efficiency of 65% or more on the EPA list. The lowest rebate of $500 covers non-cat stoves that emit between 2 and 3 grams and do not have a listed efficiency. Income-based rebates for low income residents range from $2,000 to $2,750, plus the efficiency adder if the stove has a listed efficiency.

This table is reproduced from the Change-out Program Manual (pdf).

Massachusetts provides a helpful list of rebate amounts for all stoves that emit under 3 grams an hour. There are 596 stoves on the list. As a sign of the changing face of wood stoves in America, 216 or 36% of these stoves have verified efficiencies on the EPA list. Just two years ago, in the spring of 2017, only 87 stoves had listed efficiencies of 65% or higher. 

This shows that in a short span of time, consumers have far more access to efficiency data than in the past. Change out programs like this one help drive consumers to purchase higher efficiency stoves. According to people familiar with the Massachusetts program, most consumers buy stoves with listed efficiencies rather than forgo the $500 - $750 efficiency adder.  New York and Maryland also now include efficiency criteria in statewide stove incentive programs.

In a further sign of changing times, we are seeing a major resurgence of catalytic stoves. Fifty of the 216 stoves with verified efficiencies are cat stoves, compared to 61 that are non-cat. Many manufacturers are now using the term "hybrid" for stoves that have a catalyst and robust non-cat secondary combustion. Given the spotty reputation of catalytic stoves in the 80s and 90s, some manufacturers appear to be using catalysts to pass the 2020 standards but not advertising that the stove has one. In the Massachusetts change out program, hybrids are treated like catalytic stoves and receive the higher rebate.

Pellet stoves comprise the biggest share of stoves with listed efficiencies with 95 models. This high number of pellet stoves is a reflection of the ease of getting pellet stoves re-certified to the 2020 standards, which require efficiency testing and disclosure.

Steve Pike, CEO of the
Massachusetts Clean Energy
Center announced the program at
the Fire Place in Whately MA.

Possibly the most surprising part of the Massachusetts list is that the  6 stove models under 65% efficiency are all pellet stoves. It is vital for consumers to rely on the efficiency figures on the EPA list because most stove manufacturers continue to provide exaggerated or misleading efficiencies on their websites and promotional materials. For example, the Regency Greenfire GC60 made by Sherwood Industries was tested at 60% efficiency, which had to be disclosed on the EPA list.  But the manufacturer's website says "76.6% optimum efficiency."

Massachusetts' program gives its highest stove rebate of $1,250 to "fully automated woodstoves (FAW)" that consumers can "load and leave." A FAW is defined in the program as a "stove that (a) automatically adjust the stove’s airflow and therefore includes no manual airflow controls and (b) has sensors that provide temperature-control capabilities." There are currently four such stoves on the list. Determining which stoves can be designated as fully automated is tricky. Other states and change out programs are interested in this issue as well.   The development of automated wood stoves could eventually reshape how we think about wood stoves, as they transform an age-old technology into a modern, high-tech appliance.

One important characteristic of wood stoves that does not appear on any list of stoves is whether the stove was designed for, and tested with, cordwood. Change out programs may see value in giving an extra rebate to encourage more consumers to use stoves designed to burn with cordwood instead of crib wood.

The 2019 Commonwealth Woodstove Change-Out Program has a budget of $450,000, which adds to the more than $2 million in funding for change-outs since the program began in 2012. The program has helped more than 2,300 residents swap out their non-EPA certified, inefficient stoves for newer, cleaner models. More than 500 of these rebates went to residents earning less than 80 percent of the state median income.

The program is run the by Massachusetts Clean Energy Center (MassCEC) in coordination with the Massachusetts Department of Energy Resources (DOER). Residents must have the new stove installed by a Participating Stove Professional who ensures that the old, uncertified wood stove is destroyed. There are currently 65 stove professionals participating, double the number from 2 years ago. Installers are encouraged, but not required, to be NFI or CSIA accredited.

Spotlight: A wood stove retailer sells his store and looks back four decades

Bodmer's Stoves has been located in
this stone building since 1976.

Ed and Nancy Bodmer opened a wood stove story in the mid 1970s when they discovered Ashley stoves beat out all the cheaply made stoves on the market. That led to more than four decades selling wood stoves – and experiencing the ups and downs in wood heating in America. Ed and Nancy typify the older generation of stove retailers who spanned the transition from the inefficient, uncertified stoves, to the far more efficient and cleaner ones today.  

Unfortunately, by far the biggest heyday for stove sales was in the late 70s and early 80s prior to EPA emission regulations, leaving the country saddled with millions of polluting and inefficient stoves.  Retailers like Ed Bodmer have spent decades of their lives helping with the transition to cleaner stoves.

Their store, Bodmer’s Stoves is also home to Bodmer’s Pottery, run by Nancy and is located in an old, stone building Buckeystown, 10 miles south of Frederick in rural Maryland.  We called Ed to talk to him about his experiences over the years and heard many intriguing stories.

Selling a stove store in 2019

“Actually, I didn’t want to sell this year.  I wanted to wait until 2020 when I turned 75, but this guy really wanted to the business,” Ed recalled in a phone interview. This guy owns a local heating company and he called Jotul and Vermont Castings to become a dealer.  Both of those companies said no, because Ed Bodmer had that territory.  So, his only recourse was to buy out Ed, along with all his inventory.

Ed Bodner

Getting started in the 1970s

“We kind of fell into the business, like many others, when we were just looking for a good woodstove for our own home,” Ed said.  They started with Ashley and grew to represent many big-name brands like Pacific Energy, Jotul and Vermont Casting. “We like the kind of people who are willing to cut their own wood and grow their own food,” Ed recalled.  That culture was popular in the late 60s and 70s and there is a resurgence in local food today, if not heating with cord wood.

High and lows, and diversifying the business

“The high points in our business were the late 70s, after the oil embargo and after Hurricane Katrina,” Ed said.  Katrina was a Category 5 storm that was still strong as it moved north through western Maryland in August of 2005, just before the stove buying season.  Another high point that took the Bodmer’s by surprise was the Y2K scare in 2,000, when people thought computer bugs related to the date change from one century to the next may cause major power outages and other societal breakdowns.  The lows were the mid 1980s after the oil embargo ended and fossil fuel prices went back down during what was then called the “oil glut.”  

Ed and his wife Nancy focused on running a good business from August to February so that they could have time to garden, travel and enjoy life.  They decided not to diversify into patio and barbecue products and instead focused on their core product: stoves.

The ups and downs with pellet stoves

Bodmers carried pellet stoves for many years, but demand was not consistent, and they got out of the pellet stove business several years ago.  They carried the top brands, including Harman, but even so, the repair issues were always so much higher than with wood stoves. “I’d sell a wood stove and didn’t see the person for another 20 years, when they came back to buy a newer one,” Ed recalled. 

Nancy Bodner ran a successful
pottery business out the store.

Cat vs. non-cat and first time vs. repeat customers 

Ed was very interested in our question about what percent of buyers were replacing older stoves compared to first time stove buyers.  “I’d say it’s about 50-50,” Ed told us.  Bodmers had a lot of repeat customers, but unlike retailers of most consumer goods, the stove buyer only comes back every 20 – 30 years.  But that meant a lot to Ed, and he really enjoyed those customers who he had sold to in the 1980s or 1990s.  A lot of them who bought one of the original catalytic Vermont Castings wanted another catalytic Vermont Castings.  Ed told us that a lot of his customers did their research and knew that a catalytic stove would give a longer burn and higher efficiency, and that is what they wanted.  “So, we always sold a lot of catalytic stoves,” he said.  

The 50% of his customers who were first time buyers also got a wood heat lesson from Ed, to ensure that they knew how to use the stove well.  “We don’t have a lot of young customers,” Ed said. “Most were between 30 and 60, but one guy and his wife both in their 70s just bought a new stove because they love the heat and couldn’t live without it.”

The Maryland stove rebate program

Ed said that the Maryland stove rebate program was not that much of an incentive for his customers, many of whom did not want to pull a permit and or have the professionally installed.  Bodmers used to do installations in house but has used an independent installer for the last 6 years. (The Maryland rebate program is far more used by pellet stove buyers because they get a much higher rebate.)

Inventory and the 2020 EPA emission standards

Ed told us that he had very little inventory that was not 2020 compliant and it would not be hard to get rid of it before June 2020.  Bodmer’s is not an HPPA member currently but has been in the past. By staying in close touch with the manufacturers of the stoves he sells, he has stayed abreast of all the recent changes the industry is going through. He said that ordering and receiving new stoves has become even easier these days, and he could order a few Vermont Castings, for example, and have them in the store quickly.  He also didn’t seem too worried about June 2020, when the stricter emission standards kick in. “I heard Jotul just won a Vesta award for an upgraded Oslo and I look forward to seeing that” Ed told us. He currently has an older Oslo in his home.  The only question Ed had about the 2020 deadline was whether there would be another a price increase, which would be hard for some of his price sensitive customers. 

EPA bolsters legal case for NSPS with new data

Alliance for Green Heat, July 15, 2014 - On July 1st, the EPA released a NODA – a Notice of Data Availability – consisting of data from 3 stoves tested with cordwood and 106 stoves tested with crib wood. 

Vermont Castings combustion engineer
Doug Fongeallaz uses cord wood to test
a stove instead of  Doug fir cribwood,
according to the Valley News.

The NODA is a vehicle for letting people know the EPA is relying on this evidence to make their final rule, so parties won’t be able to say that the agency surprised them, in violation of procedure for issuing new rules, if the EPA cites it.  The NODA also provides stakeholders a chance to dispute the additional evidence since it was not available at the time the rule was proposed.  The fact that EPA has published this data and the NODA in the federal register now allows EPA to rely on this data for the final rule.  It is likely that HPBA will publicly respond and a number of manufacturers and agencies are also planning on responding.

This NODA lays a better legal basis to withstand a potential lawsuit from the hearth industry and also gives more insight into what final emission standard the EPA is able to set.  Many in industry claim that the EPA does not have sufficient data to set an emission standard based on cordwood.  And some manufacturers have data but are not sharing it with the EPA in an attempt to prevent the EPA from establishing a cordwood emission standard.

Overview

This new cordwood data shows that some catalytic stoves can already meet a 1.3 grams per hour standard with cordwood.  However, the non-catalytic stove performed far worse with cordwood than it did with crib wood, with grams per hour of 4.2 on the Category IV burn, 11.7 on Category III and a whopping 39.9 on Category II.  The stove was not able to burn at Category I, the lowest air setting, either with cordwood or in the crib wood certification test.  Among the 63 non-cat stove tests released by the EPA in the NODA, only 8 of them could be tested at Category 1, the low burn rate.  It is is unclear how many of these 63 stoves can be operated by the consumer at a lower burn rate than they were tested at in the lab. The HPBA campaign to raise the minimum burn rate from 1 kg/h to 1.15 kg/h could have significantly added to the problem of stoves not being tested the way consumers often use them.

The data partially confirms what industry has been arguing – that it's still too early to set a cordwood standard for non-cats.  Firstly, there is too little publicly available data, and, even if the standard remained at 4.5 grams per hour (but with cordwood), manufacturers may not be able to make non-cat stoves that qualify. The incredibly high emissions from this non-cat stove could be a factor in leading the EPA to postpone a cordwood certification standard.  Presumably the EPA would require cordwood testing over the next 8 years and possibly make cordwood certification optional, while continuing to rely on crib certification.

The data also partially confirms what many air agencies have been saying: that some stoves can readily meet a 1.3 grams per hour standard, which is all that is legally required by the EPA to meet the best available technology test.

At the core of this issue may be the decision by EPA, not contested by HPBA, to set a single standard for cat, non-cat and pellet stoves.  There is data to show that pellet and cat stoves can meet a 1.3 standard now, but without separating them, the non-cat stoves may delay reaping the low-emission benefits of those technologies. Some manufacturers, such as Jotul, initially argued that cat and non-cat standards should be delinked, but others were against delinking, including the Catalytic Hearth Coalition.  The Alliance for Green Heat and a few others argued for a separate category for pellet stoves.  The internal politics and public rift within HPBA over this issue contributed to the industry association remaining silent on the issue of single or separate standards for cat and non-cat stoves.  Only time will tell if this is a successful legal strategy.

An attorney who specializes in NSPS law and is familiar with this case says that "the EPA could, in theory, set a legally defensible emission limit for both cat and non-cat stoves that relies on emission rates that are achievable by catalytic stoves but that may not be achievable by non-cats. EPA can’t require a specific technology under section 111, but it has the discretion to set the emission standard at a level that has only been achieved by one type of technology.  I suspect EPA would probably win on this point if challenged, however at this early stage, such predictions are still very speculative.  Ideally, there will be more data points than just 2 stoves, but I don’t think that’s going to be fatal to EPA, especially if industry isn’t willing or able to produce cordwood test data contradicting EPA’s data."

(The Alliance for Green Heat does not support a cordwood standard such as 1.3 grams per hour that some cat stoves appear to be able to meet, but regularly consults legal experts to see what EPA can do.  The danger may be that regardless of the recommendations from the EPA's stove experts based in North Carolina, far more senior EPA officials in Washington may take a much harder line.)

Summary of Woodstock Soapstone stove

Tom Morrissey, back row, 2d from
right and the team that built the
Ideal Steel Hybrid that emits less
than 1.3 grams an hour with
cordwood and cribs.

Woodstock Soapstone voluntarily provided full cord and crib wood test results to the EPA, something that perhaps no other stove manufacturer did during the NSPS process.  Woodstock Soapstone is one of the few stove manufacturers that is not a member of HPBA and thus does not follow their advice and guidance on sharing information with the EPA and what positions to take on contentious NSPS issues.

Woodstock Soapstone's stove showed a very notable consistency in emissions of grams per hour between cord and crib wood.  Certification tests using crib wood produced between 0.3 and 1.3 grams per hour for the four burn rates.  R&D testing in the manufacturer's lab with crib wood produced 0.4 and 0.5 grams per hour and between 0.5 and 0.8 grams using cordwood. 

Similarly, the stove showed high levels of consistency in efficiency between cord and crib wood and the certification lab and the manufacturer’s lab. Crib tests were between 74 and 84.5% efficiency HHV, and between 74.2 and 82.3% for cordwood for all the burn rates.

Summary of catalytic stove #2

A second, unidentified manufacturer voluntarily provided test results for 2 catalytic stoves.  A summary note from Gil Wood said, “the test data show that these two EPA-certified catalytic wood stoves when tested using cordwood - and making no design changes to adjust for crib wood versus cordwood in the tests - have similar emissions as when they were tested for the official EPA certification tests using crib wood. That is, the test data show particulate emission rates (g/hr) using cord wood that are equal to or less than the corresponding test data using crib wood for Category 1 (minimum burn rate) and Category 4 (maximum burn rate).”

The stove produced between 0.3 and 0.8 grams per hour for cord wood for Category I and IV.  A second Category IV test came in at 0.8 as well.

Summary of non-cat stove

A popular non-cat stove was purchased for testing at Brookhaven National Lab that was under contract with EPA to test cordwood in non-cats.  According to the Brookhaven test report, “the test cord wood was guided by draft cord wood specifications and procedures under active development by ASTM.  Testing was successfully completed in Method 28 Categories IV, III, and II.  It was not found possible to achieve the Cat. I burn rate with this fuel when the air control damper was fully closed. In this case Method 28 provides a method for determining average emissions based on weighting the results of the other three categories in which the stove was tested. It should be noted that in the earlier certification testing with crib wood, Category I operation was also not achieved.”

One notable result is that this popular non-cat had three very reproducible emission rates over a 3-day period.  On Cat IV, the stove produced 4.2 grams per hour on May 19th, 4.1 on May 20th and 4.3 on May 21th for an average of 4.2.  Reproducibility fell apart on Category III, with burns over 5 days producing a range from 6.4 to 17.4 grams an hour, for an average of 11.7.  Category II had slightly better reproducibility when the stove was smoldering at very high rates of particulate matter.  It produced 36-48 grams per hour over 4 days for an average of 39 grams per hour.  The high emission rates may partially be the result of fuel where the core moisture content was sometimes above 30%, although an average of core and shell was always below 25%.

The stove was also tested with very high moisture content fuel of 48.4% moisture content on a wet basis. Brookhaven found that particulate emissions were extremely high: 50.6 g/hr over the run, and 11.8 times higher than the average emission rate with the drier test fuel in Category IV.

The Brookhaven report concluded: “For optimal performance of this stove on cord wood, some rebalancing of the primary air / secondary air ratio may be required. It is possible as well that the details of the air damper setting and the procedure for loading and the timing of the startup operations contributed to differences between cord wood and reported crib data.”

Summary of 106 stoves certified by EPA since 2009

The data on the 106 stoves released in this NODA consisted of EPA approved lab certification test reports conducted since 2009.  None of them contained any data about cord wood, but this data set may be extremely important if the EPA decides to continue using cribwood to certify wood stoves in the 2015 NSPS.  Analysis of this data set could form the basis of Step 2 emission standard that is considerably below 4.5 grams per hour.  Some experts expect that the EPA may ultimately designate a standard between 2.0-2.5 grams per hour that would likely take effect in 2020. 

This data set also contained efficiency numbers that had not been reported anywhere before.  A great majority of these stoves are presumably still on the market.  The average HHV efficiency for non-cats and pellet stoves were exactly the same: 71%. Cat stoves had an average efficiency of 79%, but the sample size of 3 stoves was very small.  This data set confirmed previous data sets, that the efficiency range of pellet stoves is far wider than wood stoves.  These certified pellet stoves ranged from 62 to 80% efficient with a standard deviation of 8.5, double the standard deviation of non-cats and four times the deviation of cat stoves.  Some pellet stoves on the market have efficiencies as low as 40% and are likely to be uncertified models. The Alliance for Green Heat will be releasing a separate analysis of these 106 stoves that also shows the correlation between efficiency and emissions.

The EPA is soliciting comments on this NODA before July 31. To comment, click here.

Click here for a related story summarizing comments to the EPA about the proposed regulations.