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81 comments on Avoiding Harmful Solutions (to Our Climate and Energy Problems)
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I, for one, am skeptical of biochar. It seems like a troublesome way of achieving approximately the same affect as leaving crops or crop residue in place.
To me, this seems like a great example of the problem the story outlines. Although Tera Preta may be an ancient technology, it's sustainability has yet to be critically evaluated. The fact that the technique can be used to generate useful gases and charcoal may seem wonderful, but the other side of the balance sheet is missing. You still have to move the dry the biomass, move it around, burn it, capture the gas, and move the charcoal back to the fields. Frankly, I see some real issues for loss of nutrients. The bio-mass doesn't just contain carbon, but that's all that is being returned to the soil. For the same reason, pollution from the bi-products of burning bio-gas also concern me.
Biochar may be worth a look, but a critical review also seems necessary.
Do you really think that potassium, phosphorus and other nutrients are destroyed by carbonization? Just about everything save nitrogen remains in the solids, and we can always fix more nitrogen.
You don't have to dry the biomass much; it's just a question of how much you have to burn to drive the process. You don't have to move it much either; the process works very well at a small scale, maybe right at the field. You don't have to capture the gas (though condensing the liquids may be economically worthwhile). And it sequesters carbon on a scale of thousands of years, in a form that won't be oxidized away because someone came at it with a plow.
Biochar is definitely a silver BB.