[Terrapreta] Sustained Biochar

[Kevin Chisholm]

Dear Frank

Thanks very much indeed for your comments. They are very helpful in 
correcting what I now feel was an erroneous comment about the extent of 
methane liberated from biomass rotting on the forest floor.

Frank Teuton wrote:
> Kevin,
> 
> It is my understanding that rotting wood on the forest floor releases very
> little methane, unless that forest floor is somewhere where termites do
> their thing...The reason for this is that the forest floor environment is
> pretty much an aerobic one. Fungi do most of the decomposition work in
> rotting wood. They generally require some oxygen to be present, which means
> a methanogenic environment on the forest floor is unlikely.
> 
> By contrast, the reason hydroelectricity is less good than is commonly
> thought is because at the bottom of flooded lakes methane generation occurs
> due to the anaerobic conditions there. See
> 
> http://www.newscientist.com/article.ns?id=dn7046
> 
> for an article on that subject.
> 
> Composting similarly releases very little methane, with most of the lost
> carbon going off as CO2. Professional compost scientists are wont to point
> this out in tabulating the advantages of composting compared to landfilling
> suitable waste materials:

The composting process definitely requires oxygen... a compacted pile of 
compostables can go putrid if not turned over to oxygenate it.
> 
> http://footprint.mit.edu/waste/food/original/costbenefit.html
> 
> Landfills are the major human source of methane:
> http://www.epa.gov/methane/reports/02-landfills.pdf

I haven't read these URL's yet, but composting is somewhat different 
from rotting... correct composting targets a C/N ratio of 30:1, while 
rotting wood typically has a C/N ratio of about 300 to 400.
> 
> Although methane generation capture is improving, much leakage occurs in
> retrofitted old landfills.
> 
> I agree in principle with the idea that charcoal production should be done
> with methane capture for energy if possible, or with flaring. I believe the
> calculation of methane generation by unflared or uncaptured pyrolysis
> suggests we now discourage such practices and move quickly to engineer and
> widely distribute energy capture systems which generate charcoal as a
> sequestration and soil improvement material byproduct. These could be as
> simple as home use stoves or as complex as grid components that generate
> electricity or substantial amounts of heat, etc

Certainly, a good pyrolysis system with capture of pyrolysis gases, for 
use or flaring, with thew char going to Terra Preta is better than a 
crude or primitive system, but I would suggest that such a crude or 
primitive system is superior to a "straight combustion system", thart 
results in no removal of carbon from teh active Biosphere.
> 
> The idea that nature can handle even greater increases in atmospheric
> methane under the present circumstances is at best misguided, and at worst
> truly irresponsible.

I would respectfully disagree with you here. Even a crude pyrolysis 
system can convert 30% of total carbon to char that is effectively 
removed from the active Biosphere. Certainly, there is a 20 year "spoike 
in apparent CO2, so that after 20 years, 30% of the original is 
effectively still out of the active Biosphere
> 
> Also, I believe it is simply wrong to assert that wood decomposing on a
> forest floor leaves no soil organic matter component.

Agreed... the Lignin component of the wood is very slow to rot, and it 
certainly does provide some organic benefit to the soil.

  This is based on
> decades of forest floor observations of various kinds and also on the
> extensive use of chipped wood branches in composting and mulching. Eliot
> Coleman suggests that rotted wood can be used successfully as a peat
> substitute in growing media. I have confidence that such a material would
> have a substantial life span in soil and would contribute to further
> increased plant growth, and thus increased carbon sequestration.

This is very "advanced thinking", and is something also being proposed 
by AD Karve... add cellulose to the soil, to support soil life forms. 
More specifically, AD proposes sugar additions, but I am guessing that 
cellulose additions would accomplish generally the same things as does 
AD's sugar additions.
> 
> Researchers here have documented the benefits of additions of chipped 
> branch
> wood to soils in terms of producing long term humus.
> 
> http://www.idrc.ca/uploads/user-S/10753298271Ramial_chipped_wood_Caron_94.doc. 

Ramial wood is best supported by using "young wood" with a high 
percentage of bark.Older wood, or debarked wood, or soft woods are 
apparently very much inferior to shipped hardwood branches less than 2" 
diameter.
> 
> 
> I don't know where you got your information about wood decomposition on 
> the forest floor and methane generation/lack of soil organic matter 
> contribution, but it looks flat wrong to me.

I don't recall where I got it, but until I can get some clarification, I 
would accept that it is probably wrong. (25% methane from forest floor 
decomposition of biomass.)

Thanks again for your helpful comments. I look forward to reading your 
referenced URL's.

Best wishes,

Kevin
> 
> Frank Teuton
> 
> 
> ----- Original Message ----- From: "Kevin Chisholm" 
> <kchisholm at ca.inter.net>
> To: "Sean K. Barry" <sean.barry at juno.com>
> Cc: "Miles Tom" <terrapreta at bioenergylists.org>
> Sent: Wednesday, August 29, 2007 6:34 AM
> Subject: Re: [Terrapreta] Sustained Biochar
> 
> 
>> Dear Sean
>>
>> Isn't it better to char wood in a primitive charcoal kiln, than to allow
>> it to rot on the ground? As I understand it, (please correct me if I am
>> wrong) rotting wood on the forest floor could release perhaps 25% of its
>> contained carbon as CH4, with no carbon being retained by the soil.
>>
>> I recall seeing somewhere that the CH4 retains its increased GHG effect
>> for about 20 years, not 50 to 75 years. Could you please clarify where
>> you get this number? As I understand it, the effect is greater in "early
>> years," but that as the CH4 degrades over time, the effect is similar to
>> it being around continuously for 20 years, and then disappearing to CO2.
>>  It might be 50 to 75 years before only the last trace of CH4 disappears.
>>
>> Certainly, charring with full use of the retort or pyrolysis gases is
>> best, but I would presently appear to me that any form of char
>> production for Terra Preta is better than allowing the biomass to
>> decompose naturally, from the standpoint of GHG impact.
>>
>> Best wishes,
>>
>> Kevin Chisholm
>>
>>
>> Sean K. Barry wrote:
>>> Hi Larry,
>>>
>>> Conversion of biomass to charcoal in an "open air" retort, depending on
>>> conditions of moisture content, pyrolysis temp, and air flow, can retain
>>> as much as ~63% of the original carbon in the feedstock (giving ~25%
>>> charcoal on a weight of charcoal/weight of of dry feedstock basis).
>>> Usually under best practices, more carbon can be retained in the
>>> charcoal, than is released in the exhaust gases.
>>>
>>> The critical problem with the "open air" mound or retort is the release
>>> of UNBURNED methane (CH4), which can be a relatively small part of the
>>> producer gas output and contain a relatively small part of the original
>>> biomass carbon.  It not the amount of carbon that is the problem,
>>> though.  It is the methane (CH4) molecules that are the problem.  The
>>> reaction of burning methane is just
> <snip>
>