[Stoves] Alternatives to charcoal - transportation & biochar

[Paul Means]

Ron, in response to your questions from a few days ago:
"3.   Slide 20:     This is to ask Paul to help explain this slide.  The
obvious decrease in forest size is his (and my) main criterion.  But I am
not sure how to get numerical estimates here as the ordinate is in relative
distance, not forest area units.    Paul - Your help??"
- The interesting thing here is that it doesn't matter what the biomass
density is of the forest, the *relative cost* of hauling dried biomass to
charcoal will remain the same.  This is because transportation for both
will be proportional to the same forest density (tons/hectare) number, AND,
the area required for harvest (which is different for the different
alternatives).    If the wood to be harvested is from a densely forested
area, then the transportation cost for both will be lower.  If the wood to
be harvested comes from a sparsely forested area, then the transportation
cost for both charcoal and dried biomass will  be high.  In each case
though, the relative cost will be the same.


    4.    Paul is consuming the char, not using it as biochar.  The latter
will obviously initially require more land (probably almost twice as much)
- but this disparity rapidly disappears if soil productivity improves.
That discussion is beyond the scope of this message, but the Terra Preta
soils in Brazil are now 2 and 3 times more annually productive.   It will
not take many years for the average response to make up for the placement
of char in soil to overcome the apparent (but I believe  incorrect)
preference of some for combustion over pyrolysis alone.
- I do assume that the char from burning the dried biomass is burned as
fuel at the same efficiency as the initial burning of the dried biomass.
 It greatly complicates the comparision of the residual char must make it's
way back to the soil somewhere - especially since most of the charcoal is
burned in urban and peri-urban areas.

   5.   Slide 21 shows pellets having a *transport cost* only slightly more
for pellets over improved charcoal, but only 60% as much for traditional
char production  (Paul's distance assumed not known by me for this slide).
This is the slide I said disproved Crispin's assertions on the relative
cost of transport.  To understand when this is true we need Paul's distance
assumption.
-  This is the same situation as the first question.  You can plug in any
number for a forest density and run the numbers.  The relative difference
between  transporting charcoal, & dried woody biomass (pellets, dried
crumbled wood, etc) will be the same as long as the area the alternatives
are being harvested from are more or less contiguous with the point of use.
 In other words, if the if the harvest area for each alternative is a pie
or circular shaped area (different in each case due to the different
efficiencies of the different methods, then this will hold.  The further it
is between any harvesting and the point of use, the less this principle
will hold.  In each case one just has to run the numbers, considering the
much larger harvest area required for charcoal because of it's very low
conversion efficiency.   Sorry that I don't have time for more of
an explanation.

-  Paul

-- 
Paul M. Means
Research & Testing Manager
Burn Design Lab
(253) 569-2976 (mobile)
http://www.burndesignlab.org/
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