Discussion on Terra Preta (pollution impact)

I hope we can agree that this is a method of producing charcoal that is more apt to be harmful that helpful for climate change reasons - and therefore should not be encouraged. The ancient Indians who might have produced char in this clever way didn't have the knowledge of how bad the CO, CH4, H2 and other gases are. We should.

Bob (cc terra preta list):
Last night, you responded to my expression of concern about too-serious emissions from in-field carbonization of corn stalks, saying (with responses interspersed):

> Hi Ron
> I do not actually agree with that. In ideal controlled
> circumstances which I demonstrated earlier in my blog,
> it is possible to get a completely reduced waste gas
> that is primarily CO2. In the meantime we get a
> maximal yield of either charcoal or lower temperature
> carbonized material.

[RWL: Thanks for reminding of your blog (shown below - nice work!). I think you are referring perhaps to a Canadian incinerator two-chamber system you wrote about - the first chamber being for pyrolysis. I like that. My concern is that the "ideal controlled circumstances" you refer to are going to be very difficult to achieve in the field. I don't understand your "meantime" - but guess you believe that the emissions that I feel are almost inevitable in the field (without some controls) are justified by the produced charcoal. I still think that could have been case 1000's of years ago - but not now.

> The method just described will be fairly less
> efficient since temperature cannot be controlled and
> the combustion gases cannot be superburned. This
> produces a lot of carbon monoxide instead.
RWL: Yup - and CH4 etc. - all polluting.
> However, a subsistance farmer does not have the type
> of tools we take for granted. And this
> new(ancient)method will produce a yield likely close
> to sixty to seventy percent of the best case.

RWL: Granted - but still something to avoid. My first recommendation is that the corn stover (or whatever) is worth bringing to a central location where the CO, CH4, etc can be combusted to serve a practical purpose - cooking being one such - but maybe electrical production, etc.

> And that product, however obtained will sequester
> carbon for decades, if not centuries.

RWL: Agreed - maybe millenia. But I feel we on this list must do all we can to avoid char production that is polluting. I am certain that there will be no carbon credit funds sent when the production is done badly.

> The alternative today in most of the world is to burn
> the waste outright and in the tropics to abandon the
> field for years.

RWL: There are other alternatives. A great project for many of us is/will be to figure out best charcoaling approaches that are non-polluting, and justify the extra efforts of doing other than "to burn the waste outright and in the tropics to abandon the field for years". Thanks for carrying this idea further on your blog. Sorry to not being in support of any form of in-field charcoaling which is polluting. The work of AD Karve is not in that category - but I still hope we can find ways to productively use those valuable pyrolysis gases.

I certainly am sympathetic to the desire to minimize the out gassing of combustion products into the environment. The best use of a closed combustion oven with a second high temperature (2000 degrees)chamber to swiftly oxidize the initial combustion gases (at 350 to 600 degrees)is the one way we can do this. This will also end up been the final resolution unless we can figure out how use fusion power to do this.

The challenge is to covert tons of stover into bio char with the least amount of immediate consumption of the stover producing the needed heat.

Burning all of it as a low quality fuel simply releases all the carbon back into the atmosphere.

What those ancient Indians have gifted us with is a well proven protocol for soil enhancement and fertility retention that just happens to sequester hundreds of pounds of carbon per acre every year in perpetuity.

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