Only Sequesters Co2 For 80 Years?

[Eclipse Now]

Hi all you biochar fans,

I was depressed to read an I.B.I paper which mentioned that biochar might only sequester Co2 for 80 years? This was a paper I downloaded from IBI itself!

 

Any response from those who see biochar as a long term carbon sequestering tool?

[Essay]

Hi all you biochar fans,

I was depressed to read an I.B.I paper which mentioned that biochar might only sequester Co2 for 80 years? This was a paper I downloaded from IBI itself!

 

Any response from those who see biochar as a long term carbon sequestering tool?

 

Happy New Year!

Good Question....

A link would make a reply easier, but if I were to guess....

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I think the 80 year figure refers to the capacity of our soils to be enriched... by newly produced biochar. Then, once the soils are fully enriched with carbon, that "sink" would not be available to store more carbon.

 

That is just a "technical" limit, which means that further addition of biochar will not increase the benefits normally attributed to soils amended with biochar. More char can be added, but additional soil benefits are not accrued. So, except for the removal of a bit more atmospheric CO2, there is not as much economic incentive to make biochar.

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The 80 year figure does not refer to how long the biochar lasts in the soil. It depends on environmental conditions, but biochar half-lifes are measured in centuries to millennia. Biochar doesn't disappear, or magically turn into a pumpkin, after 80 years.

 

It might help to understand that biochar is just a poorly chosen word to describe a process that has been naturally occurring for hundreds-o'-millions of years. The byproducts of natural fires have always enriched soils; except until civilization began implementing fire codes and laws in the 1600's.

 

 

So for several hundred years now, our species has radically interfered with an ancient natural process. The soils are suffering from this lack of input from natural fires. Biochar is a way to restore that natural input of fire's byproducts into the soil, without the inconvenience of an actual "natural" fire.

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So to summarize, I'm fairly sure the 80 year figure speaks to how long our civilization can rely on the biochar/pyrolysis process to help double food production while decreasing environmental damage. It also helps reduce CO2 levels, but we still need to be fairly close to zero emissions within 80 years time--since biochar won't be viable as a big business after that point--after the soils become saturated with carbon and fully restored.

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Still, the pyrolysis/biochar process is a viable driver for creating economic value over at least several generations. That is not much worse than petroleum has done. I'm glad nobody nixed petroleum several generations ago, just because we'd hit peak oil someday; although....

 

It might be hard to read, but I liked the Economist's comment:

-click to enlarge-

 

"And there would be a nice historical justice in the substance that was displaced by coal playing an important role in cleaning up the mess that coal has left behind."

 

~ :)

[Eclipse Now]

From another commenter on another blog.

Far from being permanent, biochar is composed of largely unstable pyrolysis products, every one of them in some process of oxidation or hydrolysis. And let’s not fall for the line about “fixed carbon”, that isn’t charcoal, any more than “fixed nitrogen” is a forever job. Maybe some minority of it is charcoal, but the rest is transient. Ask for the half-life and you will get “decades” from the more respectable afficionados (“80 years” from EN’s link ) and “difficult to establish” from the scientists.

 

The PDF from the IBI has a graph on page 3.

http://www.biochar-international.org/images/final_carbon.pdf

 

The conservative half-life of the biochar itself is 80 years, moderate half life is 500 years and optimistic appears to be 500 years plus. This is the peer-reviewed work.

 

So while I love what biochar might do for soil, does it really deserve to be called a 'carbon sink' if the stuff is just going to leak back into the atmosphere within a human lifetime anyway? Where do people get the idea they can claim carbon credits if the carbon is just going to leak back into the atmosphere and not be stored on a LONG term basis?

[JMJones0424]

EN, the table that the 80 year figure comes from is clearly labeled assumptions. As for the "difficult to establish" claim, the executive summary states

How stable is it?

Studies of charcoal from natural fire and ancient anthropogenic activity indicate millennial-scale stability. However, it is difficult to establish the half-life of modern biochar products using short experiments due to the presence of small amounts of labile components, partial oxidation and biotic or abiotic surface reactions. At the moment there is no established method to artificially-age biochar and assess likely long-term trajectories.

 

So basically, unless we a.) figure out a way to artificially age char or b.) identify why all "charcoal from natural fire and ancient anthropogenic activity" is significantly different from "modern biochar products", we are left with either assuming char is char and lasts for many centuries just like all other char, or admitting that "there is no established method to age char and assess likely long-term trajectories". It is just as inaccurate to claim the half-life is 80 years as it is to claim the half-life is 500 years or many thousands of years.

 

Unless you know of a source actually claiming otherwise? I'll read the rest of the CSIRO report you linked to to see if there's anything more concrete.