Danish stove industry looks to compete, grow in America

This award winning Aduro stove accepts
wood and/or pellets and can switch
between them automatically.

Companies must navigate and anticipate shifting regulations on multiple continents

The Danish stove industry is known for sleek, vertical, expensive stoves. There is a joke that they are made to look like high end furniture that happens to hold a fire. But amidst this new wave of modern design is an industry that embraces innovation, competes worldwide to heat homes and has many budget line models.  

Danish stove makers tend to be skeptical of catalysts, very comfortable testing with cordwood, committed to quality and adaptable to the preferences and requirements of different countries. Danish stove manufacturers also have their own EPA-approved test lab at the Danish Technological Institute, one of three European labs that are now approved for EPA certification testing.    

John Ackerly, AGH President
with Jes Sig Andersen and Anne-
Mette Frey of DTI. AGH photo

One of the most exciting new Danish stoves burns both wood and pellets. It can run off pellets, just like an ordinary pellet stove, but then you can load the firebox with cordwood, drastically reducing start-up emissions. When the wood fire dies down, it will automatically revert to pellets. The stove is made by Aduro, a major European manufacturer that has not yet entered the US market but will likely do so.

Danes do not appear as intimidated by sensors and smart control systems as their American counterparts. They may appear on the market quietly, with little fanfare, and possibly without the consumer even knowing what’s under the hood. Since they require very little power, they may just have a couple batteries and don’t have to be plugged into an outlet. The trick is to get those sensors past the 2020 emissions standards with or without using a single burn rate test.

Aarhus – the stove capitol of Europe

No city in Europe is surrounded by as many stove manufacturers as Aarhus, the second largest city in Denmark. It is located on the mainland, just a few hours north of the German border. Brands well-known to North Americans include Hwam, Rais, Morsø

Aarhus is on the Jutland Peninsula, the 
Danish mainland, an academic center 
and Denmark's the second largest city.

 and Scan, but the city is also home to others that are as big or much bigger, including Aduro, Heta and Termatech. All these brands are present in many if not all European countries.  

Aarhus is centrally located with wind turbines and biomass district heating plants dotting the surrounding countryside. The hundreds of small biomass district heating plants pipe hot water underground to virtually all homes in cities, towns and suburbs. The extensive network of district heating is one of the main reasons that Danish stoves tend to be small.  Most homes already have affordable and renewable heat. Rural homes that are not on the district heating grid usually have pellet boilers, made by one of the many Danish pellet boilers companies. Danes also have innovative boilers for farms that use hay bales, another novel technology that could have a market on America’s farms.

EPA’s 2020 emission standards and foreign stoves

Danes have always tested their stoves with cordwood (only Norwegians test with cribs). The ASTM cordwood standard that allows up to 2.5 grams an hour appears to be achievable, according to Danish manufacturers. EPA certification has always been considered the gold standard in Europe and is universally accepted as the hardest test a European stove can pass.  

Jes Sig Andersen of DTI lab in Aarhus,
 left, with a technician at the Rais lab. AGH photo

The 2020 standards make it even harder for manufacturers. Danish stoves “can’t be tweaked, they need to be redesigned,” says Jes Sig Andersen, a senior specialist at the stove test lab at the Danish Technological Institute (DTI). The entire system that delivers primary and secondary air has to be reengineered and optimized to ensure maximum combustion of particulates through primary oxidation, secondary pyrolysis and often tertiary combustion. Getting that just right is a challenge even for seasoned combustion engineers, who have spent their professional lives designing stoves for the laxer protocols required in Europe.  

At a seminar hosted by DTI on stove and boiler testing, AGH President John Ackerly presented a powerpoint (PDF) on the current state of EPA regulations, potential changes, and other cordwood test methods that are in development.

Danish attitudes toward wood heating

The Danish landscape is dotted with
small biomass district heating systems,
which often use chips or hay bales.

There is an ambivalence toward wood heating in Denmark that is similar in many respects to attitudes in the US and in many European countries. Wood heating is often viewed as too polluting, a result of too many old stoves and poorly operated new ones. Pellet stoves comprise an even smaller part of the market here but pellet boilers are far more commonplace. In the capital city of Copenhagen, the mayor, like the mayor of London, is cracking down on cordwood stoves and plans to ban their future installation in part of the city. One of the largest crackdowns in Europe is in the Po River valley in Northern Italy where regular inversions trap wintertime pollution.  

The Danish government has had national change out or scrapping programs that provide a US $300 grant to simply remove an old stove, or replace it with a newer certified stove (it does not have to carry the Nordic Swan eco-label).

Vertical, clean lines and small fireboxes
dominate the Danish domestic market.

Because Denmark has a culture that looks down on overnight burns, extremely few models produced here have large enough fireboxes to do that. Some local jurisdictions banned overnight burning as it is almost synonymous with smoldering. Danes tend to want smaller stoves anyway, not as a primary or even a secondary heater as much as for the ambience. Younger Danes are more likely to install a gas stove or just a heat pump for space heating.

Danish automated stoves

The Hwam smart controller allows
the user to load and leave, and uses
sensors to adjust the air.

Aarhus stove maker Hwam was one of the first to design a fully automated stove, with an Intelligent Heat System (IHS) which competed in the first Wood Stove Design Challenge in 2013 in Washington DC. That stove helped revolutionize the concept of what a wood stove can be, and how it can be assured of operating cleanly in the hands of consumers.  Other Danish manufacturers have also used sensors and controllers that will be coming out in future models. The Hwan IHS has held its own in the marketplace, but price conscious consumers still prefer more basic, cheaper stoves.

The Aduro hybrid that burns both pellets and cordwood uses automation by necessity, so that it knows when the operator has loaded cordwood and when the stove needs to switch back to pellets.  

Henrik Norgaard, CEO of Rais
explaining their upcoming automated
stove that gives consumers confidence
in clean during technology. AGH photo

Rais has an automated stove in development that pairs Maxitrol controls with smart phone connectivity to allow users to monitor and adjust it. Basic automation can also prevent overfiring on one extreme and extended smoldering on the other, a key safety features that may catch on in the marketplace. 

A German company, Thermoelect, is marketing their automated stove in Denmark, looking for buyers who desire heat, domestic hot water and reliable electricity from a very clean burning system. That stove won first place at the 2018 Wood Stove Design Challenge in Washington DC based on its efficiency, emissions, electric output and innovative design. 

A key question is whether local and national governments will support the advancement of automated stove technologies that help stoves operate better in the hands of consumers. Automation should be

Horst Erichson holds the trophy his
automated stove won at the 2018 Wood
Stove Design Challenge. Rene Bindig
from the German Biomass Research Centre
consulted on the firebox design. AGH photo

able to help stoves pass stricter emission standards such as the EPA’s 2020 standards. Otherwise, there may not be sufficient incentives for stove manufacturers to build stoves that do much more than operate well in the test lab.  

European Union 2022 Emission Directives result in weaker emission limits in northern Europe

A weakness of European wide emission standards for wood stoves is that they are the product of a

negotiation between countries with stricter standards, and countries that have no standards at all.  One of the key purposes of the Union is to harmonize standards so that goods can flow freely between all EU countries, which means that countries cannot maintain stricter standards than others. For countries like Denmark and Germany, this can result in having to weaken emission standards. The 2020 EU Eco-Design Regulation calls for a maximum of 40 mg/cubic meter for wood stoves and 20 for pellet stoves. Denmark already requires a max of 30 and most stoves are in the 10 – 20 range. Denmark may be able to negotiate keeping their stricter standards which would also result in keeping some stoves made in other countries out of their market. But the more powerful European stove industry associations may block a country’s attempt to keep stronger standards so that they can build stoves to the laxer standards. 

One reason that European stove testing protocols are laxer is that they typically only have to test at a nominal heat output rate. They do not have to test at their lowest air setting or heat output rate. They also allow fueling to be based on manufacturers’ instructions and do not require the stoves to be filled with nearly as large loads as EPA protocols. However, there are national variations and the Norwegian national protocols required testing at 4 burn rates and with crib wood.

beReal and IDC testing protocols

Round robin testing of the same stove in different labs and
settings shows emissions are often double or triple in the real
world compared to lab testing. 

Danish stoves for export to the US are much more likely to be tested with the ASTM cordwood method, which should make them somewhat cleaner in the hands of consumers. But using cordwood and including start-up emissions is just the beginning of innovation needed in test protocols. Stricter PM limits only result in cleaner stoves if there is a level of integrity in the test method that does not exist in Europe or North America. On both continents, industry has played a big role in writing the test methods and labs in both continents have a financial stake in making sure their clients pass the test.  

The need for more real-life test methods is just as obvious to Europeans as it has become for Americans. Even before NESCAUM began developing Integrating Duty Cycle test methods, European began beReal, a very similar process to understand the weaknesses of existing lab testing and move towards a method that would result in stoves being designed for consumers, not for test labs.

An early overview of the IDC protocol
under development by NESCAUM.  The
protocol had early input from HPBA but
 they have since dropped out of the process.

A ground-breaking 2018 report, “Advanced Test Methods for Firewood Stoves” by Christoph Schmidl and Gabriel Reichert, concluded that “Real-life oriented test concepts (e.g. beReal) are capable to reflect the real-life performance of the appliances better compared to existing EN standards. An implementation of a real-life oriented test protocol as a quality label or standard should be considered as an instrument to push technological development towards optimized real-life operation and to enable a better differentiation of good and poor products for the end customer.” 

Marius Wohler, manager of the beReal
initiative speaking at the 2016 Pellet
Stove Design Challenge at Brookhaven
Nartional Lab. AGH photo

The authors suggest that establishing a voluntary test method that could be used as the basis for an eco-label could justify the costs of developing the method and provide an incentive for stove manufacturers to test to it. Wood stove eco-labels, while common in Europe, are not supported by the wood stove industry in the US, which has never had any eco-label for stoves.

The adoption of more realistic and effective test methods based on the European beReal initiative or the American Integrated Duty Cycle approach will face headwinds. Regulators may not have the time, expertise or motivation to engage in a major test method shift, and industry may resist leaving charted waters that they know how to navigate for seas that may pose tougher challenges. But both continents have persistent stakeholders and face air quality and renewable energy targets that require technologies to operate cleaner in the field, not just the lab.

Compliance audit testing or "market surveillance"

Regulators on both continents also realizing the need for compliance audits, called “market surveillance” in European parlance. Without effective oversight of test lab results, a culture of artful, possibly legal, manipulation of test protocols can grow in labs.  Once the culture exists in one lab, other labs need to follow to keep their clients from going to labs who can help stoves pass more easily.  The Alliance for Green Heat wrote about this danger in 2015 in the wake of the Volkswagen testing scandal. That scandal involved a emission testing defeat device, but it also uncovered an old boys network that stayed quiet about a culture in labs that is driven more by client pressure and expectations than government-approved test protocols.

Under the U.S. Clean Air Act, the EPA has authority to conduct compliance audit testing of stoves

A page from a 2017 Belgian list
of stoves whose sale was banned
after audit testing was performed.

and revoke a certification if the particulate matter exceeds the original lab test by 50% or more.  That provision is under litigation by HPBA and other stakeholders agree that if the PM is below 1 gram per hour, 50% is too strict given the variability of solid fuel testing.  European countries have similar compliance laws, and Belgium has begun to conduct audit testing and cracking down on stoves that it believes may have exaggerated test numbers.  They issued a seven-page document, "List of devices tested in the laboratory" (pdf) that banned the sale of nine mostly Spanish Panadero stoves in Belgium based on discrepancies in PM or CO between the certification lab and the audit lab.  

Panadero is a family run, mass market value stove manufacturer that like many other companies

The Panadero website shows the eco-
labels that some of its stoves carry.

claims to have met the 2022 standards for all its stove in 2018.  In addition, some Panadero stoves carry the French Flamme Vert and British HETAS and other eco-labels.  They apparently do not qualify for the Nordic Swan or Blue Angel.  Most of the stoves found to have a large PM and/or CO variation in 2017 Belgian audit compliance tests appear to be out of production as of 2019. One that is still in production, the Luis, does not claim to meet any European eco-labels.

Can Danish stoves gain traction in the US market?

Vertical, stylish European stoves led by Danish companies have been slow to catch on in the US market. But the entry of Danish value stove makers could change that. They already make more horizontal style stoves with larger fireboxes for the British and other markets. Danes could have a real advantage with sensor-equipped stoves that have sensors that take some or all of the “idiot factor” away from the operator. If tests can better show the value of these stoves, then it will be up to federal, state and local jurisdictions to find ways to help pave the way for them to proliferate. The recent funding opportunity from the US DOE is clearly looking for R&D in automation, and that may be a tipping point for automated stoves. Danish companies are not eligible for that, but they are well-positioned to benefit from any trend in that direction. 

European stoves may also be a beneficiary if the trade war between the US and China escalates.  

Many Danish export stoves are
more horizontal and have larger fireboxes
for Eastern European and British markets

Tariffs on steel and parts such as fans could impact American manufacturers far more than European ones, which could benefit Italian pellet stove manufacturers, for example.  

Regardless of their share of the US market, Danish stoves represent an enduring aesthetic. They are also expanding into Eastern Europe, where some of them are manufactured, and where cleaner, more efficient stoves are needed far more than North America and Western Europe. It is difficult to know how regulations, innovation and energy demands will impact wood stoves, but Danish stove makers are likely to be on the forefront of those changes.

Related stories

Alaska building list of cleaner, properly certified wood and pellet stoves (Oct. 2020)

The US needs an eco label for wood and pellet heaters (Dec. 2018)

Residential heating with wood and coal in the US and Europe (excerpts)

This blog contains excerpts from a very important and readable report published by the World Health Organization (WHO) in 2015.  It is primarily from a health and policy perspective and is very valuable for North American as it provides more of a European perspective and is balanced in its approach. The entire 58-page report can be downloaded here. 

The report is particularly interesting as it hits on many themes that were considered or included in the 2015 EPA wood heater regulations, some of which will be litigated in 2017. It addresses best available technologies, indoor air quality, efficiency standards, stove changeout programs, black carbon, carbon neutrality, HEPA filters and many other issues. One of the overarching conclusions is that national policy should strongly favor pellet over cord wood appliances, a transition that has already occurred in parts of Europe, but not in the US.

Authors include experts from the US, Austria, Canada, Finland and Germany.  This publication was prepared by the Joint WHO/United Nations Economic Commission for Europe (UNECE).

The report describes the health effects of and policy options for dealing with residential heating with wood and coal in Europe and the United States. The results presented indicate that it will be difficult to tackle problems with outdoor air pollution in many parts of the world without addressing this source sector. National, regional and local administrations, politicians and the public at large need a better understanding of the role of wood biomass heating as a major source of harmful outdoor air pollutants (especially fine particles). This report is intended to help increase such an understanding. 

Executive Summary:

Measures are available to reduce emissions of solid fuels for residential heating in most places. Encouraging fuel switching (away from coal and other solid fuels) and use of more efficient heating technologies (such as certified fireplaces or pellet stoves) can reduce the emissions from residential wood and coal heating devices. Educational campaigns may also be useful tools to reduce emissions from residential solid fuel heaters.

Furthermore, filters may reduce health effects from indoor air pollution. Existing regulatory measures include ecodesign regulations and labels in the European Union (EU) and technology based emission limits in the United States of America and Canada. Financial fuel switching and technology changeout incentives – as well as targeted “no burn” days and ecolabelling – are other tools available to policy-makers.

p. 2. Residential heating with wood is a sector in which PM2.5 and BC emissions can potentially be reduced with greater cost– effectiveness than many other emission reduction options. Nevertheless, within Europe and North America only a few countries or states have set legal limits for minimum combustion efficiency or maximum emissions of PM and harmful gaseous compounds like CO and gaseous organic compounds (see section 6).

Coal:

p. 8. In the USA 55% of homes used coal/coke for space heating in 1940, but this fell to 12% in 1960, below 5% in the early 1970s and below 1% from the early 1980s (Schipper et al., 1985; United States Census Bureau, 2011).

One study estimates that reductions in the use of bituminous coal for heating in the USA from 1945–1960 decreased winter all-age mortality by 1% and winter infant mortality by 3%, saving nearly 2000 lives per winter month, including 310 infant lives (Barreca et al., 2014).

Based on this and evidence that indoor emissions from household combustion of coal are carcinogenic to humans, the latest WHO indoor air quality guidelines strongly recommend against the residential use of unprocessed or raw coal, including for heating (WHO, 2014a).

Infiltration of smoke into homes

p. 10. A household with wood-burning appliances is likely to be surrounded by other homes with wood-burning appliances, and wood burning also tends to aggregate temporally; thus, on cold evenings and nights most homes in the area may be burning wood.

Given that most wood burning occurs in cold locations where homes are well insulated, buildings are expected to have low infiltration (meaning that relatively small amounts of outdoor air pollution, including wood-burning smoke, enter the house and contribute to indoor air pollution), especially during the heating season.

In North America heating-season outdoor temperature is an important determinant of infiltration, and infiltration levels are generally lower in the heating than the non-heating season, when doors and windows are likely to be open more (Allen et al., 2012). In British Columbia the mean infiltration fraction of PM2.5 in winter was found to be 0.28, compared to 0.61 in summer, although infiltration factors for individual homes in winter ranged from 0.1–0.6 (Barn et al., 2008); another study reported similarly low mean infiltration levels of 0.32 Å}0.17 during the winter (Allen et al., 2009). Combustion of wood in residential areas and often under cold, calm meteorological conditions can nonetheless lead to high exposure compared to other pollution sources, owing to the principle of intake fraction.

  

Indoor pollution

Modern wood stoves and fireplaces, when operated according to the manufacturers’ instructions, release some PM and gaseous pollutants directly into indoor air, although in most cases the evidence for substantial indoor emissions from these modern stoves is very limited. With poor operation, poor ventilation or backdrafting, however, elevated concentrations of combustion products (such as PM, CO, VOCs, NOx and aldehydes) may result indoors. Acute CO poisoning, which can sometimes even be fatal, may occur due to indoor wood burning and infiltration of dirty ambient air), especially when ventilation of the wood-burning appliance is not managed properly.

Stove Change outs

p. 21. Such change-out initiatives have potential limitations. The Canadian Council of Ministers of the Environment (CCME) – the association of environment ministers from the federal, provincial and territorial governments – evaluated 12 stove exchange and educational efforts conducted in Canada and concluded that exchange programmes may have limitations relating to both the cost of new technologies and the long service life of appliances once installed. The assessment supported the use of regulation effectively to curb the sale of high-emission appliances. This approach is used in a number of Canadian provinces and American states.

The Canadian National Collaborating Centre for Environmental Health found that emissions standards (based on best available technologies) are needed to ensure that the newer devices installed through change-out programmes are among the cleanest available in the marketplace. Without these standards, change-out programmes may, in fact, be lost opportunities to install the cleanest available wood-burning devices, which will be in use for years to come.

The study also found that removal of conventional noncertified appliances (through exchanges, time limits or prior to the sale or transfer of a property) was the most effective strategy included in a model municipal by-law for mitigation of residential wood smoke (Environment Canada, 2006) (see “Other regulations and voluntary measures” in section 6). [Click for more on stove change out programs - editor.]

HEPA Filters

While household or individual-level strategies are not typically part of air quality management programmes, two studies from Canada indicate that inhome HEPA filtration might reduce health impacts from wood smoke. An initial single-blind randomized crossover study of 21 homes during winter, in an area affected by residential wood combustion as well as traffic and industrial sources, reported a mean 55% (standard deviation = 38%) reduction in indoor PM levels when HEPA filters were operated (Barn et al., 2008). Use of the HEPA filters reduced indoor PM2.5 and levoglucosan concentrations by 60% and 75%, respectively. [Click for more on HEPA filters - editor.]

Regulatory Emission Limits

p. 26. Over the past decade, the European Commission has worked towards the possibility of regulating solid fuel local space heaters and boilers, particularly those that use various forms of woody biomass fuel (wood logs, pellets and biomass bricks), to create proposed ecodesign emissions limits.

According to the Commission proposals, implementation of ecodesign standards would lead to significant reductions of PM2.5 emissions from solid fuel local space heaters and boilers compared to baseline projections. The draft regulation for solid fuel local space heaters2 states that in 2030 the proposed requirements for those products, combined with the effect of the energy labelling, are expected to save around 41 petajoules (0.9 million tonnes of oil equivalent (Mtoe)) per year, corresponding to 0.4 million tonnes of CO2. They are also expected to reduce

PM emissions by 27 kilotonnes per year,

Voluntary Measures

p. 30. The Wood Stove Decathlon, an initiative of the Alliance for Green Heat, was organized in 2013 to focus creativity and resources on designing next generation wood stoves. The main goal was to challenge teams of combustion engineers, engineering students, inventors and stove manufacturers to build wood stoves that are low-emission, high-efficiency, innovative and affordable, in a common process that may point to commercially attractive next generation stove production (Alliance for Green Heat, 2013). 

Policy Needs

p. 31 Any renewable energy or climate change related policies that support combustion of wood for residential heating need to consider the local and global ambient air pollution impacts and immediately promote the use of only the lowest emission or best available combustion technologies.

Legal regulations for wood combustion efficiency in new heating appliances are urgently needed throughout the world. These will both slow down the current rapid speed of global warming (relating to BC in fine particles and VOCs that promote ozone formation) and reduce the great burden of disease caused by wood combustion-derived particles (especially organic compounds carried by BC). Such regulations should include tight – but technically achievable – limits in particular for the primary emissions of particulate mass, gaseous hydrocarbons and CO from new boilers and heaters.

p. 32. As new wood-burning devices become more energy efficient and emit less pollution (especially PM), national governments need to prepare heater exchange regulations or voluntary programmes. Municipalities, counties and states should consider requiring heater exchanges at the time of home remodels or sales. In many cases, these regulations will be most successful if financial compensation is offered to assist with the cost of replacing old heaters with those meeting tight energy efficiency or emission limits regulations.

“No burn” areas are needed. Especially with current combustion technologies, it is important to define urban areas with dense populations and/or geographical features (such as valleys between mountains) where residential heating or cooking with small-scale appliances burning solid fuels (wood and coal) is not permitted at all or is at least limited to registered models of low-emission wood combustion devices. Residential heating with coal in small-scale appliances should also be permanently prohibited, at least in communities of developed countries, as should the use of wood log burners for central heating without a sufficiently large water tank (which otherwise leads to badly incomplete combustion and very large emissions).

Co-benefits for health and climate

As wood is burned ... carbon is released back to the atmosphere, not only as CO2 but in most household combustion also in the form of short-lived greenhouse pollutants such as BC, CO and VOCs including CH4. Thus, to be perfectly “carbon neutral”, wood fuel has to be not only harvested renewably but also combusted completely to CO2. For both climate and health purposes, the form these fuels’ carbon takes when it is released matters greatly, since BC and CH4 are both strongly climate-warming.

p. 34. A World Bank study found that replacing current wood stoves and residential boilers used for heating with pellet stoves and boilers and replacing chunk coal fuel with coal briquettes (mostly in eastern Europe and China) could provide significant climate benefits.

Another study coordinated by the United Nations Environment Programme and the World Meteorological Organization found that widespread dissemination of pellet stoves (in industrialized countries) could improve health, since these interventions lead to reductions in PM2.5.

If Arctic climate change becomes a focus of targeted mitigation action (because of threats from rising sea levels, for example), widespread dissemination of pellet stoves and coal briquettes may warrant deeper consideration because of their disproportional benefit to mitigating warming from BC deposition in the Arctic (UNEP & WMO, 2011). The World Bank found that replacement of wood logs with pellets in European stoves could lead to a 15% greater cooling in the Arctic (about 0.1 ÅãC). For Arctic nations the modeling strongly indicates that the most effective

BC reduction measures would target regional heating stoves for both climate and health benefits (Pearson et al., 2013).

Conclusions

p. 35. Given that residential wood combustion for heating will continue in many parts of the world because of economic considerations and availability of other fuels, an urgent need exists to develop and promote the use of the lowest emission or best available combustion technologies.

 It may be preferable in many cases to focus on making biomass-based home heating more efficient and less polluting rather than transitioning away from biomass to fossil fuels, given the climate change implications of using fossil fuel for heating.