The greenest way to make a holiday fire.

Illuminating answers to environmental questions.
Dec. 22 2009 9:31 AM

Hearth Burn

The greenest way to make a holiday fire.

The holiday season means one thing to me: Sitting around the fireplace, slowly getting sloshed on eggnog. I keep seeing fake logs for sale, made from "green" materials like recycled cardboard or coffee grounds. Are these synthetic products really any greener than a piece of real wood?

You'll forgive the Lantern for starting this column with a bit of sensible home-heating advice: A Yule log burning in the hearth may be festive, but it's a terribly inefficient source of energy. (All that air getting sucked out through your chimney means your home may actually end up colder than it would be otherwise.) If that's not enough to dissuade you from making a holiday fire, you may as well choose the most responsible source of fuel. Yes, it's true—those eco-friendly fake logs can be better for the environment than real wood. But so were those retro petroleum-and-sawdust Duraflame logs from the 1970s.

Illustration by Rob Donnelly. Click image to expand.
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Real wood's green credentials are obvious: It's renewable and doesn't require much processing before you stick it in your fireplace. Some commercial producers do use kilns to dry their firewood, rather than letting them air dry, and transporting logs over long distances can be energy-intensive. With a little effort, though, you can probably find a locally sourced option —or source some firewood from your own backyard. Even the wood sold in big-box stores tends to be pretty eco-friendly when it comes to resource use, as it's typically low-quality timber that manufacturers won't otherwise use.

Fake logs are also pretty efficient when it comes to resources. In fact, they were invented in the late 1960s by a cedar-products company looking for ways to use up the detritus from pencil making. A traditional log substitute would be made by mixing some of this sawdust with an equal amount of petroleum wax, another manufacturing byproduct. In other words, it's made entirely of recycled industrial materials. (You can also find 100-percent-sawdust logs, but those are more commonly used in wood stoves rather than fireplaces.) There is a downside: The sawdust and wax must be mixed and then extruded, molded, or compressed to get those clean, pretty tubes—a process that requires additional energy. And thanks to their petroleum content, fake logs produce significantly higher greenhouse gas emissions (PDF) than natural firewood.

In recent years, manufacturers have been fiddling with the basic makeup of wax-fiber logs and trumpeting the green credentials of the resulting products. Two popular offerings, as you note, are logs in which the sawdust has been replaced with coffee grounds and ones in which both the sawdust and the wax have been swapped out for ground-up waxed cardboard boxes. A third option is to replace the petroleum wax with a plant-based binder, as Duraflame has done with all its logs.

The coffee and cardboard logs have an obvious appeal, since they're made from waste products that would otherwise be headed to a landfill. (Waxed cardboard boxes, used to transport fruit and vegetables, generally aren't recyclable.) Logs with natural waxes also make use of low-grade byproducts, such as solid palm stearine (from the refining of palm oil), tall oil (from the processing of soft pine into paper), and fatty tallow (from butchered cows). These ingredients have the benefit of being renewable and not derived from fossil fuels, but they could pose a problem if those crops were not harvested sustainably. For example, palm oil has been linked to deforestation and habitat destruction in Southeast Asia. And some green-minded consumers might not be comfortable with the use of animal products to sustain their holiday fire.

Still, as we've seen, nearly all fireplace fuel options help wring the maximum use out of raw materials. So no matter what you toast your S'mores with, the Lantern thinks you can generally feel OK about it, in an I'm-using-every-part-of-the-buffalo kind of way.

So far we've talked about what goes into a log; now let's consider what comes out of it. You might think that burning natural firewood would produce the cleanest emissions. In fact, the opposite is true. When organic material doesn't burn all the way through, it releases tiny bits of particulate matter—linked to lung and heart disease, not to mention burning eyes and runny noses—and other hazardous substances, such as carbon monoxide, benzene, formaldehyde, and polycyclic aromatic hydrocarbons. Concerns about emissions from fireplaces are great enough that some communities call for "burn bans" on days when the air quality is particularly low.

Artificial logs emit all the same pollutants as natural firewood, but they do so at significantly lower rates. A 2005 report from the EPA and Environment Canada (PDF) analyzed emissions from several varieties of fake logs, including those made from sawdust and coffee grounds, and compared them with reported figures for firewood. On average, a fire built with fake logs emitted 9 grams of particulate matter per hour, while wood-fueled fires emitted 36 grams. The fakes also released less carbon monoxide: 42 grams per hour, compared with firewood's 214 grams. The fakes also produced much less carbon monoxide, benzene, formaldehyde, and polycyclic aromatic hydrocarbons.

There were some differences observed among the fakes, though. The coffee logs, for example, produced slightly less particulate matter than the others and had the second-lowest carbon monoxide, formaldehyde, and polycyclic aromatic hydrocarbon emissions. However, the differences between the best- and worst-performing fakes were much smaller than the differences between the most-polluting fakes and firewood.

Franken-logs tend to outperform their natural cousins because they pack in much more energy per unit of weight, on account of their wax content and relative lack of moisture. That means you don't have to burn nearly as much fake wood to get an equivalent amount of heat and light. The fake logs also burn more completely, producing fewer pollutants.

If you already have wood piling up in your backyard, however, the Lantern thinks you should use what you've got rather than buy a fake log that's less polluting. Just make sure that tree came down early in the year. Wood that's properly dried, or "seasoned," burns more cleanly and efficiently. (Getting your fire as hot as possible, as quickly as possible, will also reduce emissions.) The EPA's Burn Wise campaign recommends splitting wood into logs  3 to 5 inches in diameter and then storing them outdoors, covered and off the ground, for at least six months before burning. If you have a lot of wood and use your fireplace often, you might consider investing in a moisture meter. Otherwise, knock two logs against one another—if they're dry enough, they'll make a hollow sound, as opposed to a dull thud.

Is there an environmental quandary that's been keeping you up at night? Send it to ask.the.lantern@gmail.com, and check this space every Tuesday.

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Nina Shen Rastogi is a writer and editor, and is also the vice president for content at Figment.

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