BioBrick Heat Content vs Firewood
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%
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%
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 Firewood Heat and Weight Values put together by the California
Energy Commission. The table lists the weight and BTU values of 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
The heat value for a cord of 12% moisture Ash is 25 million BTUs at an
average weight of 3,000 pounds. This works out to 8,333 Btu's per pound.
The manufacturer's heat estimate for one, two pound BioBrick is 17,000
BTUs, or 8,500 BTUs 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 output of BioBricks closely approximates that of most firewood.
While reading the
homepage of the BioBrick
website, I noticed an
interesting statistic used to
describe 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*."
moisture content of 21%)