The Colour of Carbon: Biochar and Terra Preta

 Source: Next 100 Blog

November was a bit busier than expected, so once again this blog got laid aside in favour of my work.  Lets see if I can keep it going a bit longer this time.

Biochar, a charcoal-like substance made from biomass and used as a soil amendment, has been credited with multiple benefits, including the ability to improve soil fertility, protect water quality, and generate carbon neutral energy. (NRDC)

Over the past year, there have been more than a few articles (and many more blog posts) touting the benefits of biochar as a solution to at least some of our climate change woes.  perhaps the most authoritative source was published in Nature Communications in August this year.  The title - Sustainable Biochar to Mitigate Global Climate Change - suggests the-best-thing-since-sliced-bread hype about the possibilities of biochar.  The authors, Woolf, et. al. estimated the maximum sustainable potential of biochar to mitigate climate change being equal to up to 12% of current anthropogenic greenhouse gas emissions, i.e. nearly 2 giga tonnes per year.  James Lovelock, the father of the Gaia concept went even further, suggesting:

There is one way we could save ourselves and that is through the massive burial of charcoal. It would mean farmers turning all their agricultural waste - which contains carbon that the plants have spent the summer sequestering - into non-biodegradable charcoal, and burying it in the soil. Then you can start shifting really hefty quantities of carbon out of the system and pull the CO2 down quite fast. . . . This scheme would need no subsidy: the farmer would make a profit. This is the one thing we can do that will make a difference, but I bet they won't do it. (As quoted in Next 100 blog)

The biochar concept certainly has a pedigree thats a bit longer than that of you average offset.  Biochar is believed to have been first used as far back as 450 BC among Amazonian Indians as part of the mix that created Terra Preta, or dark earth in Portuguese.  Even today, thousands of years later, many Terra Preta soils still demonstrate big improvements in soil fertility over the surrounding soils and are reported to be dug up and marketed as superior compost in the Amazon region. (Interestingly, the benefits of Terra Preta have caught the eye of modern gardeners and the web has lots of sites offering direction on making your own biochar.)

Source: Biochar info

But now NRDC has come along to rain on this particular parade.  Despite the glowing quote in biochar's favour at the start of this post, NRDC raises concerns that include:

• Land use conversion and the carbon emissions that can result;
• Loss of biodiversity associated with development of monoculture plantations that might be created to maximize biochar production;
• Fugitive losses of biochar during transport and application;
• Carbon loss from soil disturbance during biochar application;
• Lack of understanding of emissions resulting from biochar production; and
• Difficulty of monitoring and verifying biochar offsets.

The NRDC justifiably seems to be concerned about the unintended impacts once a dollar figure, or more likely, a euro value gets attached to biochar offsets - think ethanol or some recent offsets in China.

The solution that NRDC recommends is U.S. federal funding of $100 to $150 million for five to 10 commercial scale pilot projects.  Looking at the specifics, NRDC suggests that large-scale pyrolosis and gasification units using slow pyrolosis, i.e. at temperatures of approximately 500⁰ C appear to be the most favourable technology.  With respect to feed stocks, and there are many, many possibilities to choose from, they suggest residual biomass that is already somewhat concentrated such as animal manures, sewage sludge, organic municipal solid waste and urban wood residue offer the best candidates.

If you are interested in biochar, its well worth taking a look at.

 

Comments

[adam_john]

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[landboy09]

I heard about biochar a few months ago from a friend of mine. I never thought that something as simple as charcoal could do so much for the soil and the environment.

I was amazed after reading "The Biochar Revolution" from http://biochar-books.com/The_Biochar_Revolution.

They have a great discount for Christmas on the book at the moment.

Check it out. It was a great help in opening my mind to issues that affect us all.