[Stoves] Alternative to charcoal

[Paul Anderson]

Dale and all,

Thank you for your input, especially the quantitative parts.   I confirm 
and agree with your comments, such as about 1 inch maximum of diameter 
of wood in the residential size TLUDs.

I hope that more people will be considering alternatives to charcoal.

Paul

Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
Website:  www.drtlud.com

On 4/8/2013 4:09 PM, Andreatta, Dale A. wrote:
>
> At the recent ETHOS conference Paul Means and Chris Lanning gave a 
> very thought-provoking talk about an alternative to charcoal.  The 
> basic idea was to use a gasifying stove with prepared wood fuel.  The 
> prepared wood fuel would be bought by the user instead of charcoal, 
> and the supply chain would be similar to charcoal.  The big advantage 
> is that the very inefficient step of charcoal production is 
> eliminated.  The stove would hopefully be easy to use and would smoke 
> very little, so as to retain the benefits of a charcoal stove.
>
> Their proposed fuel was crumbled wood, which would work well, but 
> seemed to me to require a lot of big machinery and capital. How could 
> one go from a tree to a fuel that would burn well in a gasifier with 
> as little work as possible, and without too much costly equipment?  
> The fuel  should be as low or lower in cost than charcoal per unit of 
> food cooked, and give a better ratio of food cooked per unit of tree.
>
> I did some preliminary experiments.  With 779 g of natural wood from 
> the trees in my yard, I used a Paul Anderson Champion gasifier and 
> boiled 5 liters in 21.4 minutes (corrected).  After an easy light the 
> stove burned steadily with no attention, other than turning down the 
> primary air when boiling started.  About 10 minutes after boiling the 
> pyrolysis ended and I transferred 123 grams of char sticks, glowing 
> only weakly, into a charcoal stove, and continued simmering until 
> nearly 2 hours after the start of boiling. I had good turndown on the 
> charcoal stove and a lid on the pot.  There was a little smoke during 
> the pyrolysis phase, but not too much.  This seems like excellent 
> stove performance.
>
> Had I used a very good charcoal stove to perform a similar task, it 
> might have taken 240 g of charcoal.  This would take about 1800 g of 
> wood if the charcoal were made efficiently, or 3000 g if it were made 
> normally.  (Reference Means and Lanning on the efficiency of charcoal 
> production.)
>
> The wood I started with was about 1 inch diameter (2.5 cm) by 6 inches 
> (15 cm) long, cut from my trees and dried outdoors but under cover for 
> some months.  I didn't measure the moisture content, but a previous 
> oven-drying test with similar wood showed about 12-14% moisture.  A 
> previous test with larger diameter wood didn't go well, so I think 
> this is about the maximum possible diameter.  I don't know how long it 
> took to get to this moisture content, not months I'm sure, but at 
> least some number of days.
>
> The production method for this alternative to charcoal would be to use 
> a chain saw to cut wood into convenient lengths while in the forest, 
> then take it to a central place.  Here, use electric saws and/or 
> hydraulic  splitters to cut the wood to the appropriate size.  Give 
> the wood a modest amount of drying in the sun, or in some simple 
> oven.  The wood might have to finish drying at the place of use.  I 
> expect that split wood would dry faster than cut sticks, since the 
> moisture doesn't have to pass through the bark. Alternatively, use a 
> chain saw and engine powered splitter to cut the wood to size in the 
> forest, then transport to a central place for drying.  When fairly 
> dry, transport the wood to the users as with charcoal.  During 
> transport, the energy per unit weight would be lower than charcoal, 
> but the energy per unit volume would be similar.  The user might be 
> given the option of buying shorter sticks for cooking smaller meals, 
> or longer sticks for larger meals.
>
> In comparing the economics of this method to charcoal, I would think 
> of the cost of the fuel as coming from 5 elements; the cost of the 
> trees, the cost of the processing equipment, the cost of the labor, 
> the cost of the transportation and distribution, and the cost of the 
> stove.  If the trees are free, then the fact that you don't cut as 
> many trees doesn't help much.  If the trees must be paid for, then 
> this method looks more attractive.  The processing equipment for 
> charcoal is virtually free, but hopefully this method doesn't take too 
> much equipment.  The labor for this method might be similar to 
> charcoal, but it might be less because you are cutting and processing 
> a lot fewer trees to serve the same number of customers.  
> Transportation would be more expensive, since you are shipping more 
> mass, though not a lot more volume.  This method would require a 
> gasifier or T-Char stove, which would be an expense, though hopefully 
> not a lot compared to the annual cost of fuel.
>
> Thus, if the trees must be paid for, this method might be attractive 
> to the consumer of the fuel, the producer of the fuel, and to the 
> forest.  If the trees are not paid for, this method looks less 
> attractive, though the forest would still benefit and some outside 
> subsidy might be available.
>
> Dale Andreatta, Ph.D., P.E.
>
>
>
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