Tuesday, July 27, 2021

EPA's cordwood test protocol for wood stoves moves forward

 AGH wrote to the EPA in June and again in early July, requesting public information about the stove testing that it is undertaking.  We had seen numerous references about the stove testing but could not find more details about it.  Rather than submitting a Freedom of Information request, which would likely provide a jumble of emails and miscellaneous documents, we urged the EPA to provide an overview.  Details about the EPA’s stove testing program are well known by HPBA insiders, and by staff at NESCAUM and NSERDA, yet we have consistently found that the EPA, nor those organizations, share information very well. This blog may be updated soon with rejoinders from experts who take issue with the EPA's narrative.  

This letter from the EPA partially explains how and why the EPA approved an IDC (ALT-140) test method without a full certification test report using that method.  NYSERDA and NESCAUM still have not produced certification level test data for their IDC method "although we [the EPA] understand that Alaska will be providing us with additional data demonstrating use of the ALT-140 for compliance testing."  

In the past 10 years, the EPA has rarely had any budget for lab testing, so its current budget of one million is significant.  AGH believes that its imperative for the EPA to develop its own data and not just rely either on industry or groups like NESCAUM and NYSERDA.  We reproduce below the email verbatim from Stef Johnson, leader of the EPA's Measurement Technology Group.  The photos were added by us.

July 20, 2021

Dear Mr. Ackerly: 


Thank you for the questions you forwarded in your July 9, 2021 email.  I appreciate the thoughtfulness of you questions and the opportunity to engage with you on this important topic.  In particular, I’d like to clarify the steps in EPA’s processes for: 

·         New Test Method Development and

·         Alternate Test Methods (ATM) 


New Test Method Development 


In the method development process, EPA creates new measurement methods for regulatory purposes.  In the case of EPA developing new test methods for wood heaters, EPA has embarked on a public process that engages stakeholders as we develop a new measurement method for this sector.  EPA’s Measurement Technology Group, the group I lead, began the process by convening a Roundtable consisting of manufacturers, Hearth Patio & Barbeque Association (HPBA) staff, state and local regulators, test lab technical staff, and multijurisdictional organization (MJO) representatives.  The Roundtable participants gathered to discuss the use and vetting of the Integrated Duty Cycle (IDC) method for certification of wood fired stoves and consider making that testing approach an EPA test method.   


After the January 2020 meeting where we discussed the IDC approach and the ASTM E3053 test approach, the agency determined that we would pursue development of the IDC as an EPA method.  We have been working in that direction ever since.  The process to conduct method precision testing of an IDC for wood heaters, one for hydronic heaters, one for forced-air furnaces, and one for pellet heaters is resource intensive and complex.   


EPA remains committed to transparency and open dialogue as we explore and develop new methods for compliance testing of wood heating appliances.  We have provided the Roundtable group information about our Quality Assurance Project Plan (QAPP), the IDC method for wood heaters -- the current subject of our trials, and the Tapered Element Oscillating Microbalance (TEOM) Standard Operating Procedures.  We have also shared supporting spreadsheets for using these methodologies.  We have posted this and other information in a public docket (EPA-HQ-OAR-2016-0130) and we have begun using this posted IDC, along with TEOM measurements in our contracted laboratory.     


The EPA is paying for 26 tests at PFS-
TECO testing in Portland, OR.

We are conducting 52 tests (26 paired tests) at a West Coast lab (PFS-TECO) and will be comparing those data to a duplicate effort that will be funded by NYSERDA and conducted at ClearStak laboratories in Connecticut.  Within each lab, we are doing paired testing to look at intra-laboratory variability -- known as repeatability testing.  We will be comparing the inter-lab variability (method reproducibility) between these bi-coastal sets of 26 test pairs.  This helps us understand the test method performance with respect to overall variability and informs our decisions as to the appropriateness of the test method for use with a given emissions standard.  EPA has committed nearly $1,000,000 to the West Coast portion of wood heater test method work, and to a study of TEOM precision to be done at EPA’s facility in Research Triangle Park, NC.  This type of data has never been collected for any wood burning appliance test method to date.   


All data we develop from our trials will be publicly available and placed into the same docket as the QAPP and IDC /TEOM methodologies.  We will convene the Roundtable after the wood heater precision testing is complete and we have data to discuss.  Certainly, there will be lessons learned along the way and improvements made.  As you may know, NYSERDA is also conducting wood heater precision testing, and we expect that they will make their data public.  East Coast testing will likely begin in mid-September.  We anticipate that a full data set will be available for discussion by in early 2022.  Again, this is for the development of a wood heater IDC compliance test method.  Finally, we will propose, take public comment, and finalize a new compliance test method.  All of this will be a public process, and all of the data will be available for review.   

NYSERDA is paying for 26 tests of
the same stoves at ClearStak in
Connecticut.  ClearStak offers
transparency in testing by video taping 
the tests but it is not known if these 
tests will be videotaped or if the tapes
will be released to the public.


Alternative Test Methods 


The Alternate Test Method (ATM) approval process is different than compliance test method development.   In the ATM process, the requestor is responsible for providing sufficient information to the agency to demonstrate that the proposed Alternate Test Method is appropriate for compliance testing purposes.   Requesting an ATM is an option available to any affected party. The proposed ATM must be deemed by the Measurement Technology Group to be appropriate with the final air pollution standard.  The entity requesting the ATM must demonstrate compliance with a Federal subpart regulated by 40 CFR Part 60, such as subparts AAA or QQQQ regulating wood burning residential heating appliances. 


EPA’s Measurement Technology Group receives requests for alternate means of compliance testing from affected source categories, from electric utilities to wood heater manufacturers and everything in between.  We are responsible for reviewing each request and make a technical determination about the appropriateness.  We either work in a direct back/forth manner with the requestor or we agree to the request with some stipulations. (You will note we listed several in our 2021 ALT-140 approval letter).  


In sum, the ATM approval process is a technical exchange with a requestor followed by a technical evaluation by my staff.  The goal is to approve compliance testing that meets a specific need and is appropriate for the compliance purpose as outlined in the rule.  While such evaluations may involve exchange of data between the requestor and EPA, each request is evaluated and assessed on a case-by-case basis.  


In situations where there is not any test method available, for example, EPA will evaluate the request differently than in situations where we have already approved an ATM.  With regard to ALT-140, we have had the opportunity to learn about the IDC development process through multi-party meetings from 2017 to 2020.  The information shared during this time about the IDC illustrated that this method provides a more rigorous test assessment of heater performance and therefore, provides a more conservative compliance demonstration approach.  Such conservative approaches (more difficult to pass the test) are nearly ideal for Alternate Test Method processes because one of our goals with the ATM process is to not relax the standard in any manner.   


That said, when EPA received Alaska’s request to approve an alternative test method for demonstrating compliance with the New Source Performance Standard Subpart AAA, Standards for New Residential Wood Heaters in December 2020, we were not aware of data that demonstrated that a wood heater could meet the emissions limit of the rule using the IDC.  Therefore, we asked Alaska to provide us with that information.  While what they provided to EPA is not an entire test report, it is credible enough for us to allow the use of the test method for compliance demonstration, where a compliance test must fully document all of the test method QA/QC details to satisfy EPA’s Office of Enforcement and Compliance Assurance (OECA)’s requirements.   


Finally, using an ATM itself is optional and my staff ensures that all alternative methods are equivalent or more stringent than the test method in the EPA regulation.  No one need ask to use one unless they decide that it is in their interest to do so.   In the case of the Alaska request, EPA’s approval of ALT-140 provides a cord wood compliance pathway for manufacturers wishing to sell in the Fairbanks-North Star area.  They are also free to conduct crib fuel tests and sell crib fuel tested units in that area.   


Finally, EPA has received 5 spreadsheets from NYSERDA/NESCAUM in support the Alaska ALT-140 request and they are available upon request.  To date, EPA has not received any other NYSERDA/NESCAUM test data used for their IDC method development purposes, although we understand that Alaska will be providing us with additional data demonstrating use of the ALT-140 for compliance testing.  


I hope this has been helpful for your understanding.   


Very sincerely, 


Steffan Johnson

Leader - Measurement Technology Group

US Environmental Protection Agency (EPA)

Related stories

Nine states urge the EPA to revoke the ASTM cordwood method (May 2021)

EPA announces overhaul of wood stove certification process (April 2021)

AGH response to NESCAUM report on wood stoves (March 2021)

EPA and states vigorously defend audits of wood stoves (Sept. 2020)

EPA finds lapses in cordwood certification testing (July 2019)

Friday, July 9, 2021

Vermont and Maine retain top rank in residential wood heat, while New Mexico climbs to #3

Wood heat provides resilience, benefits to utilities as climate change quickens

An analysis of U.S. Census data by the Alliance for Green Heat shows that wood heating is expanding in some states and shrinking in others between 2009 and 2019.  Generally, it is expanding in northern New England and shrinking in the Pacific Northwest. In areas that experience frequent weather inversions causing excessive smoke build up, like Oregon and Washington, fewer homes heating with wood is good news for local air quality. In New England states where it is expanding, it's good news for agencies and groups that want to more aggressively reduce fossil fuel heating, and invest heating dollars in the local economy. 

Overall, the number of homes that use wood or pellets as their primary heat source dropped from 2% to 1.6%, with low fossil heating fuel prices likely being the top factor.  From 2000 until about 2012, wood and pellets were the fastest growing heating fuel in the United States. According to the U.S. Energy Information Agency, 8 states experienced more than 100% growth and 7 states experience between 50 and 100% growth from 2005 to 2012.

Vermont and Maine have long been ranked #1 and #2 for per capita primary wood heating with 9% and 13% of homes as of 2019.  New Mexico rose from #6 in 2009 to #3 in 2019, passing Montana, Idaho and Oregon.  It experienced a 14% rise in primary heating during that decade whereas Montana, Idaho and Oregon dropped 14%, 10% and 17% respectively.  Poor economic conditions in Native American Reservations may account for some of New Mexico’s per capita rise.

Wood and pellet heating is widespread and culturally accepted – it is used in about 10 million homes – and consistently offsets a significant amount of fossil heating fuel every year. Now, the electrification movement is leading to more and more homes heating with heat pumps. In the coming decades, until renewable electricity is more available, wood and pellet heat can help utilities by lowering wintertime peak demand.

Census data on the rise or fall of per capita primary wood and pellet heating only tells parts of the story. Stoves are used far more often as secondary heaters and can be a secondary heater one year and a primary one the next, depending on fossil fuel prices or a household’s ability to pay for fossil fuels. It also doesn’t necessarily reflect the sale of stoves, or how many people buy new stoves to replace old ones, buy stoves for secondary homes, or switch from wood to pellet stoves, for example. According to the Energy Information Administration (EIA), about 3 times more homes use wood as a secondary fuel than a primary one.

It is still unclear how climate change and slowly warming winters will impact wood heat. The federal government and states may increase rebates for the cleanest and most efficient units, since wood and pellet stoves are a very cost-effective way to reduce fossil heating fuels. Additionally, stoves that used to be secondary heaters may now become primary heaters as more and more households need to use their furnace or boiler less.  Other factors that are expected to lead to more stove sales include the increasing severity of major storms and blackouts and the widespread switch to electric heat pumps.  Many households with heat pumps want back-up heat, cheaper heat during the coldest months, and a more intensive heat source.

Northern New England states have already started to incentivize more pellet heating to invest in local energy jobs, reduce reliance on carbon-intensive oil and propane heat and help build the infrastructure for modern pellet heating systems. Those states do not have the level of wood smoke problems that some western U.S. areas have.

The list of the per capita top 10 wood heating states has also seen some reshuffling over the past decade. The popularity of wood relative to other home heating fuels increased in some states and declined in others. 


2009 Rank

2019 Rank

Change in Percentage of Homes Heating Mainly with Wood 










New Mexico












New Hampshire








West Virginia




















In the past ten years, New Mexico overtook Montana, Idaho, and Oregon to become the state with the 3rd highest percentage of homes heating with wood. Wood’s popularity has declined in West Virginia, Wyoming, and Washington, while increasing in Alaska, Vermont, New Hampshire and Maine. 

The home heating question has been a Census question since 1996, and the question and definitions have not changed since then. As a result, pellets are not specifically mentioned, though the Census definition says: “This category includes purchased wood, wood cut by household members on their property or elsewhere, driftwood, sawmill or construction scraps, or the like.” Therefore, we assume that people answering this question today will say they use wood if they use pellets.

Regarding older Census data, it is difficult to find historical annual state-level data that are 10 years or older. Data from 1999 is available for download online but in aggregate form with unlabeled questions. The 2020 Census data will be released starting in September, though some of the data will not be released until January of next year. The data used to compare household wood heating 2009 and 2019 is from the American Community Survey (ACS), which the Census Bureau conducts every year. One-year ACS wood heating estimates are less accurate because the respondents are fewer than the official decennial “Census,” which only happens once every 10 years. 

Further reading:

Households heating with wood or pellets declined by nearly 10% between 2011 and 2016

EIA: 2014 Increase in wood heating most notable in the Northeast

2012 Census Shows Wood Heating Continues Growth Streak

2011 Census Shows Wood Heat Continues to Rise in U.S.

2010 Census Shows Wood is Fastest Growing Heating Fuel in US

Coal Heating in the United States (June 2017)