[SustainableTompkins] Biochar (Terra Preta)

[Joel and Sarah Gagnon]

I was initially somewhat skeptical, since biochar isn't very "natural". 
While there may be a bit of charcoal produced in forest fires, it isn't 
common. Reading about the Amazon soil experience was reassuring, though. I 
remember being taught that tropical soils are poor because of the 
tremendous leaching action of high rainfall. Incorporating a durable 
nutrient sponge would be tremendously valuable in that situation and 
potentially many other situations as well. It may well be that the effects 
of such soil modification will turn out to be overwhelmingly positive and 
synergistic, as with normal organic matter additions. Given the historical 
record of what amounts to a long-term experiment, I would agree that there 
is plenty of reason for optimism and experimentation in temperate climates. 
Given that the economics to drive the process are not yet in place, we have 
the time to get on with that before scaling up massively.

Wasn't coal gas production a form of low-temperature pyrolysis? One 
byproduct of that process was coal tar, which we are still cleaning up 
decades later. Of course, I wonder how harmful it really is, given that it 
is a big part of many driveway sealers. Clearly the process has to be done 
in a way that results in the "right" end products. How easy is that?

Joel

At 09:35 PM 5/14/07 -0400, you wrote:
>You get energy *out* by partially burning biomass in a way that
>sequesters CO2 *and* improves the soil for hundreds of years.
>What's not to like?
>
>Jon
>
>==================================================================
>
>http://energybulletin.net/29673.html
>
>A handful of carbon
>Johannes Lehmann, Nature
>
>...An existing approach to removing carbon from the atmosphere is
>to grow plants that sequester carbon dioxide in their biomass or
>in soil organic matter2. Indeed, methods for sequestering carbon
>dioxide through afforestation have already been accepted as
>tradable 'carbon offsets' under the Kyoto Protocol. But this
>sequestration can be taken a step further by heating the plant
>biomass without oxygen (a process known as low-temperature
>pyrolysis). Pyrolysis converts trees, grasses or crop residues
>into biochar, with twofold higher carbon content than ordinary
>biomass. Moreover, biochar locks up rapidly decomposing carbon in
>plant biomass in a much more durable form4.
>
>The precise duration of biochar's storage time is under debate,
>with opinions ranging from millennial (as some dating of naturally
>occurring biochar suggests) to centennial timescales (as indicated
>by some field and laboratory trials)5. Whether biochar remains in
>soils for hundreds or thousands of years, it would be considered a
>long-term sink for the purposes of reducing carbon dioxide
>emissions.
>
>...Biochar is a lower-risk strategy than other sequestration
>options, in which stored carbon can be released, say, by forest
>fires, by converting no-tillage back to conventional tillage, or
>by leaks from geological carbon storage. Once biochar is
>incorporated into soil, it is difficult to imagine any incident or
>change in practice that would cause a sudden loss of stored
>carbon.
>
>The bottom line is that plant biomass decomposes in a relatively
>short period of time, whereas biochar is orders of magnitudes more
>stable.
>
>...At the local or field scale, biochar can usefully enhance
>existing sequestration approaches. It can be mixed with manures or
>fertilizers and included in no-tillage methods, without the need
>for additional equipment. Biochar has been shown to improve the
>structure and fertility of soils, thereby improving biomass
>production3. Biochar not only enhances the retention6 and
>therefore efficiency of fertilizers but may, by the same
>mechanism, also decrease fertilizer run-off.
>
>For biochar sequestration to work on a much larger scale, an
>important factor is combining low-temperature pyrolysis with
>simultaneous capture of the exhaust gases and converting them to
>energy as heat, electricity, biofuel or hydrogen
>
>...The consequences of climate change are already being felt1 and
>there is an urgency not only to identify but also to implement
>solutions. Biochar sequestration does not require a fundamental
>scientific advance and the underlying production technology is
>robust and simple, making it appropriate for many regions of the
>world. It does, however, require studies to optimize biochar
>properties and to evaluate the economic costs and benefits of
>large-scale deployment.  (9 May 2007)
>
>The full article is behind a paywall. A good place to start
>looking for more information is Professor Lehmann's homepage.
>
>Contributor SP writes:
>For the Terra Preta fans out there.
>
>
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