EPA certified wood stoves manufactured today typically emit 2 – 4 grams per hour, roughly ten times less than the 15 to 40 g/hr that older stoves typically emits. However, about 80% of the residential wood stoves manufactured prior to the EPA standards are still in operation 6, potentially posing health risks to local populations while at the same time negatively influencing public opinion about the viability of wood heat as a clean renewable energy technology. Wood stoves tend to last a long time and are replaced less frequently than other major appliances, so many of the older stoves are still used regularly for heat. For this reason, the replacement of older stoves (see Chapter 5, Section A: Changeout Programs) and the removal of loopholes that allow unregulated new stoves to stay on the market (see Chapter 6, Section F: Exempt Woodstoves) are vital to improving air sheds across the country.

The EPA jump-started cleaner residential stoves in 1988 with their New Source Performance Standards, and is only now revisiting these regulations in 2011. The original standards dictated a maximum of 7.5 g/hr for non-catalytic wood stoves and 4.1 g/hr for catalytic wood stoves. Many stove types were exempt from regulation for various reasons (see Chaper 6: Appliance Types). The proposed New Source Performance Standards are likely to at least partially follow the lead of Washington State, where, in 1995, officials sent a strong message to the industry and Federal Government by setting stricter standards for wood stoves sold in the state. The current emissions standard in Washington is 4.5 g/hr for non-catalytic wood stoves and pellet stoves and 2.5 g/hr for catalytic wood stoves. The burgeoning residential biomass boiler market in Europe provides clear evidence that wood stoves have the capacity to become much cleaner (see Chapter 5, Section D: European Incentives).

Like all forms of renewable energy, wood heat is well suited for some areas of the country, but not so well suited for others. Strict regulations on new installation of cordwood appliances in certain major urban non-attainment areas like Los Angeles and Denver, as well as valleys subject to inversions is often a necessary air quality step, though the cleanest pellet appliances may still be permitted. These local restrictions also prevent incentive programs, like the federal tax credit, from incentivizing installations in places that already have very poor air quality.

For purposes of this report, incentive programs that involve government funding offer a clear opportunity to mitigate health impacts of high emitting wood burning appliances by leveraging public funding to maximize benefits of wood heat while minimizing the potential health impacts. Strategies include making only the cleanest appliances eligible or by only incentivizing pellet stove installation in urban areas, but not installation of wood appliances unless they meet or exceed air quality restrictions and are accompanied by wood moisture requirements. In Europe, extensive incentives for qualified pellet appliances has likely steered many consumers towards these very clean burning appliances. The same could hold true in the United States.