Change Alley

information, opinion, conversation

Carbon Sequestration The Old Fashioned Way

with 6 comments

Forget all those fancy ideas about pumpng CO2 into holes in the ground. A millenia-old technique could hold the key to our greenhouse gas problems and declining soil fertility .

Terra Preta is the name given to the areas of fertile ‘dark earth’ scattered throughout the Amazon basin, which explain how Indian peoples were able to sustain high agricultural outputs on generally low-fertility soils. Biomass-derived carbon (“bio-char”) was dug into the earth in huge quantities. Recent research shows that bio-char can persist in the soil for thousands of years, improving soil structure and fertility.

terra-preta.jpg

Millions of tons of agricultural wastes are discarded annually which can be used to produce bio-char and applied to soil. In the modern version of this age-old process, agricultural wastes and bio-energy crops can be used to produce energy by charring them in specialised power plants yielding bio-char as a by-product. The bulk of the energy would be extracted as hydrogen or bio-diesel at potentially very high levels of efficiency.

www.css.cornell.edu/faculty/lehmann/terra_preta/TerraPretahome.htm

For a second opinion, go to:

www.garyjones.org/mt/archives/000273.html

Generally favourable, with the additional interesting information that bio-char may not be suitable on all soil types as it increases alkalinity.

And a link to a Nature article with details of the processes involved here.

Advertisements

Written by Pete Smith

January 19, 2007 at 12:11 pm

6 Responses

Subscribe to comments with RSS.

  1. My latest activities include being drafted as coordinator by these guys at REPP Crest http://info.bioenergylists.org/?q=about . the TerraPreta mail list terrapreta@bioenergylists.org , The whole REPP thing started just a few days ago , so we will see who comes to the party.

    This is the forum the REPP guys drafted me from, some 15000 views and 300 replies :Hypography Science Forums – Earth science
    http://forums.hypography.com/earth-science/3451-terra-preta-31.html

    Erich J. Knight

    January 21, 2007 at 11:26 pm

  2. Terra Preta

    At Last a Nature article link that will Last

    Another “link that will last” is at the bottom of this 1/19 blog post:

    environmentdebate.wordpress.com/2007/01/19/carbon-sequestration-the-old-fashi…

    Science Forums

    January 22, 2007 at 1:11 am

  3. The quote below from the Science Forums page linked to summarises my thoughts on the subject;

    ‘The only real way to allow for farm land to stay fertile is either through artificial fertilization (not the best) or a cycle of crop rotation and allowing fallow periods upon the field.’

    Interestingly this is one of the concerns of Biofuelwatch members; that fallow land will get taken up for expansion of rapeseed for the new biofuel directive.

    On another point regards fertilization. The cake left over from sewage works cleansing processes is used on farms as a fertilizer. Plenty of that where it came from!!

    matt

    January 22, 2007 at 10:32 am

  4. Matt, I’m really not sure what you’re trying to say here. Yes, artificial fertilisation is to be avoided if possible, but terra preta involves adding natural substances to the soil. Yes, crop rotation and fallowing, for terra preta projects just as for all crops, including biomass for biofuel. Yes, sewage treatment by-products are applied to the land, as they have been for years, along with animal slurry. The problem with that is these fertilisers decay and give off greenhouse gases. Bio-char does not.
    As the title of my original post suggests, terra preta is a carbon sequestration technique, with soil fertility and energy as spin-offs. However, it might be seen differently, perhaps as an energy-extraction technique with a sequestration spin-off.The Nature link has an interview with a guy who is actually doing it, he’s deliberately tuned the process so that it “emulates nature” and isn’t optimised for any of the 3 ‘products’.
    This is an exciting prospect. Who knows, in the near future we could have farmers being paid for carbon sequestration, rather than paying out mega bucks for oil companies and other contractors to bury CO2 underground, as the Australian government has recently done.

    Pete Smith

    January 23, 2007 at 12:54 pm

  5. Ok, read the Nature article in detail & for me anyway, it basically confirms my initial laymans gut reaction to the topic of your post; biochar in the Amazon happened slowly over 1000s of years thanks to human communities & their waste. How then could anyone rush such a process for the benefit of the climate now?

    Half way through the Nature article (& this is anarok stuff) I come across a possible answer in the company, Eprida and its work. They make char as a by-product of biofuel production from crops and spread the char back onto the soils of the farm. Fine. Then I’m wondering about fuel use from machinery used to spread the char & most importantly there’s (at that point in the article) no mention of tilling. I mean, in the Amazon the biochar is buried and it’s this that gives the soils its incredible fertility.

    Then the answer comes regards tilling on the last page of the article at the suggestion of a principal speaker. The journalist of the article has the impression the enthusiasts at the conference hadn’t even considered this! As the speaker points out the char needs to be tilled in so that it doesn’t blow away and its benefits are realised. Carbon sequestration … OK, but what about the fuel emissions created to do this?

    It’s early days yet and there seem to be a lot of different ideas coming to this. I feel we are entering a ‘gold rush’ of ideas generation for limiting the impacts of climate change. Bring it on! But lets hope we don’t waste too much energy going down too many cul-de-sacs (as the Nature journalist implied 🙂 ) So, lets hope biochar isn’t one of them.

    matt

    January 23, 2007 at 1:52 pm

  6. Cul-de-sac? Hardly. Bio-char can be added to soil along with conventional top dressings, which consequently stay in the soil longer, requiring less frequent applications and reduced inputs. It can be left on the surface to be drawn down by natural processes, or mixed mechanically during normal tilling. It can be left piled up in a corner, it still sequesters carbon.
    This is a completely scalable process, ranging from a small charcoal heap on a small-holding to large industrial operations. The whole point is that carbon in the form of charcoal can persist in the soil for centuries. The fact it improves crops is a bonus, as is the energy derived from the pyrolisation process.

    Pete Smith

    January 23, 2007 at 2:52 pm


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: