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% 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
Firewood Heat and Weight Values put together by the California Energy Commission.
The table lists the weight and Btu value of 39 types of firewood at 12% moisture
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 is 25 million Btu's at an average weight
of 3,000 pounds. This works out to 8,333 Btu's per pound.
The manufacture's heat estimate for one, 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
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 of
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%)