Soil-based solutions
May 11, 2007, 5:23 pm
Filed under: Farming, Interventions in the carbon/climate crisis

Via Gary at Muck and Mystery, various reports on the conference on biochar/agrichar/terra preta nova/what-you-will that just ended down in Australia. If you’re not up to speed on this, the general idea is that people could help solve a great many problems by putting enriching soils with reduced carbon in charcoal-like form. This gets rid of the carbon for a long time (charcoal is very refractory) and improves the soil in various not yet fully understood ways. My colleague Emma wrote a lovely feature on the subject last year. There’s what seems to be a thriving discussion board on the subject at Hypography.

The conference was opened by Tim “Weather Maker” Flannery, which is a pretty big name for a new field to manage to attract, I’d have thought. Here’s an overview of the conference by Kelpie Wilson of the Energy Bulletin. One interesting aspect is the idea of tying this issue to the issue of crappy stoves that drive indoor air pollution and waste a lot of energy.

Transect points, a blog by soil scientist Philip Small who, like Gary, is tracking this issue, has more reports in a round-up. As one of the people quoted says, the great thing about this field is that it opens up in so many different directions. Its also low tech enough to be of real use globally. The flip side of that is that different techniques will be needed in different places — this is unlikely to be a one-size-fits-all technology.

As it happens we’ve a look at the subject in Nature this week, too — a commentary (pdf) from one of the field’s main men, Johannes Lehmann of Cornell, which takes things forward nicely, I think. One of the advantages he points out for biochar sequestration — as opposed, say, to sequestration of carbon in aquifers — is that once the carbon is in the soil “it is difficult to imagine any incident or change in practise that would cause a sudden loss of stored carbon”. And he also argues that this sort of practise could be carried out at a serious scale:

I have calculated emissions reductions for three separate biochar approaches that can each sequester about 10% of the annual US fossil-fuel emissions (1.6 billion tonnes of carbon in 2005). First, pyrolysis of forest residues (assuming 3.5 tonnes biomass per hectare per year) from 200 million hectares of US forests that are used for timber production; second, pyrolysis of fast-growing vegetation (20 tonnes biomass per hectare per year) grown on 30 million hectares of idle US cropland for this purpose; third, pyrolysis of crop residues (5.5 tonnes biomass per hectare per year) for 120 million hectares of harvested US cropland. In each case, the biochar generated by pyrolysis is returned to the soil and not burned to offset fossil-fuel use. Even greater emissions reductions are possible if pyrolysis gases are captured for bioenergy production.

Similar calculations for carbon sequestration by photosynthesis suggest that converting all US cropland to Conservation Reserve Programs — in which farmers are paid to plant their land with native grasses — or to no-tillage would sequester 3.6% of US emissions per year during the first few decades after conversion; that is, just a third of what one of the above biochar approaches can theoretically achieve.

Those, Lehmann stresses, are rough calculations to highlight the potential, not realistic scenarios. But might it not make sense to start developing them into realistic scenarios? If you have inexpensive feedstock, this is a pretty intriguing technology.


3 Comments so far
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Hey, great overview of Biochar. I’ve been reading up on the subject with much interest and I decided to write a brief on my ScribeMedia blog.

URL: http://www.scribemedia.org/2007/06/27/biochar/

I would love to do some on-camera interviews with those people involved with Biochar and maybe some feature content about its history and current development.

If anyone out there is currently involved in Biochar research and/or development, please contact me @ curtiss[at]scribemedia.org.

Thanks a lot. Again, great post!

Curtiss P. Martin
Editor – Clean Technology

Comment by Curtiss P. Martin

[…] in biochar has been building up in the UK recently. There was a cover story by Fiona Harvey in the FT a month […]

Pingback by The biochar backlash « Heliophage

Every farm owner and hobby farm owner can contribute their part to store carbon in their soil. Few months ago the temperature at Melbourne, Australia went up as high as 45 degree Celcius, never before in the history. We should take Climate Change seriously and do whatever little part we can to help save the planet earth

Comment by Ben

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