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Firewood Heat Value vs BioBricks

By on March 7, 2009

Firewood is the original renewable fuel and still being used as the sole source of heat for approximately 1.5 million homes. Recently, an eco-friendly alternative to firewood has been introduced to the consumer under the brand name BioBrick.


If you’re not familiar with BioBricks, they can be described as a two pound, 2″x4″x6″ brick made from compressed sawdust – just like wood pellets. The bricks are stackable, burn clean with less than 1% ash, and cost around $300 for a 1,900 pound pallet.

While reading the homepage of BioBrick’s website I noticed an interesting statistic used to qualify the heat content. Here’s the heat claim quoted from their website:

“One pallet of our BioBricks(TM) brings as much heat into your house as one cord of wood*.”

*(typical cordwood moisture content of 21%)

What got my attention was the 21% figure they offered as the typical moisture content of cordwood. Any homeowner heating with wood knows that firewood isn’t considered seasoned unless the moisture content is 15% or less.

Maybe the 6 points separating the two examples doesn’t sound like much, but wood with 21% moisture content is actually 40% wetter than the 15% variety.

I don’t think the BioBrick people were trying to intentionally mislead consumers. It just sounds better from a marketing stand point to say one pallet of BioBricks delivers the same amount of heat as cordwood with 21% moisture content rather than a pallet of BioBricks delivers 94% of the heat of properly seasoned cordwood.

But what happens when you compare the heat output of BioBricks with well seasoned, 12% moisture cordwood?

For comparison purposes I’m going to use the Btu heat numbers from a table of “Wood Heating and Weight Values” published by the California Energy Commission. The table lists the weight and Btu values for 39 types of firewood at 12% moisture content.

However, a cord of firewood rarely consists of only one species which makes it difficult to accurately determine the Btu value. In order to even things out, I’ll compare the heat value of BioBricks to Ash. Ash is a middle of the road hardwood and, heat wise, is halfway between Live Oak and Western Red Cedar.

The heat value for a cord of 12% moisture Ash with an average cord weight of 3,000 lbs is 25 million Btu’s. This works out to 8,333 Btu’s per pound.

The manufacturer’s heat estimate for a two pound BioBrick is 17,000 Btu’s, or 8,500 Btu’s per pound – almost identical to Ash. (By the way, I picked Ash first and ran the numbers, not the other way around).

Although my methods are hardly scientific, I think it would be fair to say the heat value of BioBricks closely approximates that of most firewood.

If you’ve already tried BioBricks, please post a comment and share your experience.

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