Ever since the first caveman threw a log on the first fire, burning wood for heating and cooking has helped to define human civilization. But wood as a fuel source has some inherent drawbacks, especially the gases, particulate matter and other pollutants produced by burning logs.
A new generation of high-efficiency wood stoves, however, has become available that are as low in emissions as they are high in energy efficiency. And as the Environmental Protection Agency (EPA) introduces new regulations designed to make wood stoves even more efficient, people are rediscovering wood as a smart, renewable source of energy.
Last week, the EPA proposed tightening its emission standards for wood stoves: Currently, the EPA certifies wood stoves that produce no more than 7.5 grams of fine particulate matter per hour, but new regulations would reduce that level to 4.5 grams per hour by next year, the Fairbanks Daily News-Miner reports, and lower it again to 1.3 grams per hour by 2019. [Top 10 Alternative Energy Bets]
The EPA's new restrictions, however, appear unlikely to diminish the popularity of wood stoves as a heating source: The use of wood as a primary residential heat source in the United States has grown by 39 percent since 2004, according to the Department of Energy, and about 8 percent of homes nationwide now use wood as a secondary source of heat.
And in certain cold, forested regions, wood is even more popular: Almost 50 percent of homes in rural New England, for example, use wood (either cord wood or wood pellets) for space heating, water heating or cooking. As the cost of heating oil rises, more homeowners can be expected to add wood stoves to their residences, either as primary or supplemental heat sources.
Out with the old, in with the new
But not all wood stoves are built alike, and there's virtually no comparison between the wood stoves made after 1988 — when the EPA first issued performance standards — and the smoky wood stoves of earlier years.
Older wood stoves burn wood inefficiently and must be fed fresh logs on a regular basis to keep a room warm. Additionally, older stoves generate much more air pollution — as much as 70 percent more — and are notorious for smoking up the inside of homes almost as much as the outside.
The superiority of next-generation wood stoves was on full display last November in Washington, D.C., where the contestants in the 2013 Wood Stove Decathlon gathered to show off their technological superiority. The competition was sponsored by the departments of Energy and Agriculture, Popular Mechanics magazine, the Alliance for Green Heat and other groups. [US Renewable Energy Consumption (Infographic)]
Some models on display used computer technology, gas-flow analyses or catalytic converters to reduce emissions and increase efficiency. An entry from the University of Maryland used a thermoelectric generator (TEG) — which derives energy from the heat of the stove — to power a fan that pulled warm exhaust air back into the stove, improving efficiency while also conserving heat.
A new Woodstock generation
Competition winner Woodstock Soapstone of Vermont, however, improved on existing technologies to create a stove that achieved an impressive 82 percent wood-burning efficiency, while generating only 0.54 grams of particulate emissions per hour, according to Popular Mechanics.
"It's a complicated stove that we needed to simplify down to its main components," Woodstock Soapstone president Tom Morrissey told Popular Mechanics. "We asked ourselves: 'Are we trying to wow the judges, or are we making something that's really simple?' We went with simple, and it worked very well."
While Woodstock Soapstone's winning design, dubbed the Ideal Steel, isn't yet available to the general public, when it does go to market (sometime later this year), it should retail for less than $2,000. That amount could represent a considerable energy savings for people who live in cold climates and/or drafty houses. And a federal tax credit, as well as some state and local government incentives, make wood stoves an even more attractive alternative.
Which wood stove? Pros and cons
Newer wood stoves generally fall into one of two categories, either catalytic or non-catalytic. Catalytic stoves send smoky exhaust through a ceramic honeycomb catalyst (not unlike the catalytic converter on a car) that burns off the gases and particulate matter in the exhaust, and as a result emits fewer pollutants.
Non-catalytic stoves have interior baffles to produce a longer flow path for hot gases, which causes more of the exhaust's gases and particulates to burn. Air flowing into the stove is also pre-heated, increasing the efficiency of the stove.
Both types of wood stoves have advantages and disadvantages: While catalytic models generally have longer burn times and higher efficiency than non-catalytic wood stoves, catalytic models can be higher maintenance, since the catalysts need to be replaced every few years (depending on how often the stove is used, type of wood burned, etc.). And models that rely on electricity to operate will, of course, be non-functional in the event of a power outage.
The EPA and wood stove manufacturers recommend that consumers burn only the right wood for their stove (generally dry, seasoned hardwood), use a certified technician to install the wood stove, and have the stove and chimney inspected regularly to prevent chimney fires and ensure proper operation.