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)

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.