[Terrapreta] Farm Produced Biochar

Thu Aug 16 18:52:57 EDT 2007

Just a wild idea...this sounds crazy...in fact the whole idea is  
ridiculous...

I keep thinking about the difference between a mobile pyrolysis unit  
vs. a fixed one in terms of making char out of field residues.   
Actually, both require field biomass, eg. corn stover, to be baled  
and brought to a point, and then later picked up again and re- 
distributed on the field.  It would be much neater, if we could  
justify a simple charring unit solely for char production, but only  
if there is a flow through process such that one could drive through  
the field towing this unit, continually processing crop residues as  
one is driving, and spreading the char as it goes....Now that would  
be a real "mobile" charring unit!

But I would have no idea how to make this actually work!  Even if it  
is possible, it probably be much too expensive of an idea!

Just dreaming,
Gerrit

On 14-Aug-07, at 5:13 PM, Tom Miles wrote:

> Richard,
>
> Agreed. Production and use of the charcoal on the farm is not  
> trivial. It's
> at a different scale than commercial charcoal production but it is  
> done with
> a purpose. That purpose is clearly defined in your case. It is not  
> yet clear
> in many cases.
>
> The actual cost may exceed the current returns on the investment of  
> labor
> and capital but the value (cost/benefit) may not be calculated in  
> strictly
> current economic terms. That's not uncommon when developing new  
> technologies
> or applications, so I jokingly say that it must be amortized on its
> entertainment value. The point is that there must be a purpose, a  
> product
> and a value.
>
> Serious farm production of biochar in our area will be regulated in a
> similar manner as outdoor wood boilers: systems will have to comply  
> with
> air, soil and water quality regulations. The amount of regulation will
> depend on the scale of the charcoal production. Let's look at scale.
>
> In your plots you have used 30 gallons (4 ft3) or 60 lbs (4 ft3 x  
> 15 lb/ft3)
> of charcoal in 85 ft2 plots (5 x 17ft= 4). 60 lb/85 ft2 = 0.7 lbs/ 
> ft2 equal
> to about 14 tons of charcoal per acre. If your planted area is 50%  
> of the
> total area you would use 7 tons of charcoal per acre.
>
> If you used a kiln the size of Robert Flanagan's (1.5 tonnes [1.65 t]
> biomass per charge) you would produce about 0.66 tons per day (at two
> charges/day) or 20 tons of charcoal in 30 days
> http://terrapreta.bioenergylists.org/flanaganvinegar
> So if you ran Flanagan's kiln for 30 days at two charges per day  
> you could
> treat about 3 acres per year (20 tons/7 tons per acre). In 15 years  
> you'll
> cover the whole 45 acre nursery. 1.65 tons/8 hours with wood vinegar
> recovery would exhaust about 3 MMBtuh which is large enough to be  
> regulated
> in some states.
>
> If you treat 5 acres per year that's 35 tons of charcoal per year
> representing 175 tons of biomass (35 tons charcoal/20%) per year.  
> If you
> make your own charcoal at 5 tons of charcoal per day (175 tons/30  
> days = 5.8
> t/day) each kiln charge would be about 25 tons of biomass/24 hours  
> or 1 ton
> per hour (2 big bales). Your kiln will be rated at about 12 million  
> Btuh
> (80% biomass x 15 MM Btu/ton x 1 ton/hour) if no oil is recovered,  
> or 5
> million Btuh if just the offgas is burned to drive the process of  
> making oil
> and char. Either way you have an system is large enough that it  
> will be
> regulated for particulate, CO and NOx emissions.
>
> A system of this size is likely to be operated as a stationary  
> production
> facility operating 250 days per year (6250 tons biomass or 1250 tpy
> charcoal). Large bale combustors of the 1980s (Agrifurnaces, IA)  
> were rarely
> moved. Most systems included debalers like the farm scale straw  
> burning
> gasifiers and boilers or today.
>
> A farm scale charcoal system might include the same amount of  
> equipment as
> Vidir's Greenhouse Gas Displacement system which gasifies straw to  
> replace
> natural gas for heating heat poultry houses.
> http://www.vidir.biz/index-biomass.htm Vidir's smallest system  
> consumes 500
> lb/hr (3 Million Btuh) of wheat straw. If built as a pyrolyzer it  
> would
> produce 100 lb charcoal and 1-2 million Btuh heat. The system cost is
> $200,000. Annual operating cost with straw at $10/bale is estimated at
> $16,000. Labor is figured at 3 hours per day $15/hr. Economics are  
> based on
> 6 months operating time (in Manitoba) or 375 tonnes (752 x 500 kg
> bales/year). At 20% yield that would produce 82 tons (75 tonnes) of  
> charcoal
> which could treat about 12 acres (at 7 tons/acre). In four years  
> you would
> produce enough charcoal for a 40 acre farm. At $200/ton the  
> charcoal would
> be worth about $16,400/year whch would just offset the operating  
> costs but
> not capital. If you had a use for the heat (2 million btuh x 70% to  
> hot
> water = 1.4 MMBtuh, 33.6 MMBtu/day) in 30 days you would recover  
> more than
> $12,800 additional revenue to help pay for the plant. In six months  
> you
> would recover $16,400 in charcoal value and $76,800 in heat  
> savings. So the
> payback could be 4 years with heat recovery.
>
> To a see a system like that in operation would be entertaining.
>
> Regards,
>
> Tom
>
>
>
>
>
>
>
>> Entertainment is something like chasing a ball with a stick - what we
>> are doing is a bit more than that.
>>
>> Rich H
>
>
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