[Stoves] 4 Charcoal production, improved

[Robert Penn Taylor]

Jeff Davis wrote:

 > I see charcoal as a good thing. The problem is our methods of
 > production NOT charcoal. Charcoal can and has been produced very
 > efficiently and clean!
 >

Not to be a wag, but "very efficiently" compared to what?  Kerosene? 
LPG?  Ethanol?  Raw biomass?

In terms of conversion efficiency of sunlight, charcoal is a big loser 
to raw biomass.  The problem is not just methods of production, there's 
a usable-energy issue here too.  The method of charcoal production 
affects the amount of energy "wasted" in the production process along 
with the emissions profile.

One way of addressing the question of whether charcoal is "a good thing" 
as opposed to direct combustion of biomass is to look at the transport 
distance.

If the fuel doesn't have to be transported very far, raw biomass has a 
higher total efficiency than charcoal.  As the transport distance 
increases, raw biomass begins to lose out due to the fuel required to 
transport the much heavier load.  What is the critical distance at which 
the total energy efficiency is the same?  Depends on species, transport 
method, efficiency of production process, efficiency of stoves at the 
point of use, etc.

Of course energy efficiency isn't everything.  Add in the question of 
emissions and the issue certainly gets more complicated.  Are point 
sources preferable to non-point sources?  Are there critical levels of 
each chemical in the emissions?  What about CO?  Etc.  I'm unconvinced 
that it's so simple as regarding charcoal as "good" or "bad".  Much 
depends on the particular situation.

-Penn Taylor