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Compressed Sawdust Logs

Q: Great FAQs. Thanks. Here's a new one: Does burning densified logs (hardwoods, no-wax type, basically a giant pellet) have any benefit? Supposedly they burn hotter lb-for-lb than cord wood. But, can they get too hot for a typical stove? Or is that a matter of air control? Do the hotter exhaust gases mean that the creosote which is in the lignin, and which is forced into the outer surface of the log during compression, will burn more readily and completely? The logs are clean and easy to store; probably more expensive per BTU than hardwood. But maybe the benefits are worth it. I've seen these logs for the first time this year here in New England, so I'm also thinking that they might be a good item to carry and sell in my business (I'm in the paint supplies business). What do you guys think of them?

Jim Stratton
Merrimack, NH

SweepyHi Jim,

Thanks for the inquiry! Actually, the compressed sawdust logs don't burn hotter, pound for pound, than seasoned cordwood. Each LOAD might produce more heat, however, because each compressed log is heavier (contains more wood fiber) than an equivalent-sized piece of most species of cordwood. This advantage is counteracted somewhat by the fact that some of the resin content (and its heat value) is baked out of compressed logs during the kilning process.

When comparing compressed logs to cordwood, the best measure to use is btu content: most compressed logs contain about 17 million btu/ton. This is about the same btu content as a cord of Douglas Fir or Pitch Pine at 20% moisture content, as shown on the fuelwood btu charts in our Sweep's Library. Thus, if your price for a cord of Douglas Fir or Pitch Pine is about the same as your price for a ton of compressed logs, your fuel cost would be equal. If you can get a cord of Doug Fir or Pitch Pine for less than the price of a ton of compressed sawdust logs, you'd get more fuel value for your money by buying the cordwood. Similarly, if you can get any of the higher-btu content species shown on our chart for the same price as a ton of compressed logs, you'd be money ahead burning the cordwood.

What sells the compressed logs is the no-bugs, no-dirt factor, and the fact that compressed logs are ready to burn when you buy them (they don't require seasoning, like cordwood does). We've burned them, and found them to be a viable, if a bit pricey, alternative to cordwood. We have observed no difference in creosote formation between compressed logs and properly seasoned fuelwood.


12/13/12: A letter from a compressed log company in England

It would have been good if you had mentioned that when you purchase cordwood you are buying 25/30% water whereas with compressed sawdust logs like ours you only get 6%. Who wants to buy gallons of water?

You mention Douglas fir and Pitch pine with no reference to their ability to spit hot embers half way across a room and burning holes in the carpet: not so with Eco-logs.

Flue temperatures are generally higher with Eco-logs so reducing chimney tar.

I like your site.

Hope all is well in Washington.

Kind regards

Eco Logs UK

SweepyHi Chris,

You Brits are famous for your tongue-in-cheek sense of humor, so I'm not sure if you're trying to raise serious points, or just "having me on."

Your claim that people who buy cordwood are buying water simply doesn't hold water. Cordwood sells by volume, not weight. When you buy a cord of wood, you're buying a stack measuring 4' wide x 4' tall x 8' long. Since those dimensions don't change appreciably as the wood seasons and the water evaporates away, whatever water content is present in the wood when you buy it costs nothing.

Carpet burns are not an inevitable result of burning "pitchy" wood. The high-efficiency stoves and fireplaces we sell all have transparent ceramic doors, which are more than strong enough to contain any hot embers that might spit out of a burning piece of pitchwood. Our friends who burn pitchy wood species in open fireplaces have enough sense to use a mesh or glass firescreen to likewise contain any spitting embers.

Finally, all that is required to minimize creosote formation in the flue is to keep the exhaust above condensation temperature. Any extra heat lost up the flue is heat lost to the room.

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