Log in

Previous Entry | Next Entry

Biochar: A Blink to MEGO?

kmo had another great podcast over at the C-Realm the other day, interviewing long-time guest Albert K. Bates. This time Bates talked about something of which I've heard not even a peep: Biochar.

From one of his blog posts on the topic, Bates describes biochar as a charcoal formed from inactive, crystalized carbon. The end result of the biochar process produces a fractal structure with amazing longevity and pourosity: "One gram of biochar has a surface area of 1000 square meters." Once amended to the soil, this surface area provides the dirt with great advantages for growing plants, including crops:

In the soil, biochar’s cavities fill up with nutrient foodstocks for microbes, much like a kitchen pantry. The microbes move in, and pretty soon hyphae of fungi appear. The hyphae are a fast road for nutrients and moisture – a trade exchange route to plant and tree roots. Examination of biochar-amended soils a few months after treatment found that vigorous fungal colonization was common.

If you can imagine the char as providing a coral reef-like structure, full of tiny polyps and crevices, it attracts all manner of soil organisms to it. If the pantry is empty, then those microbes will go to work to stock it, which is why biochar denitrifies over-fertilized, burned out farmland and replaces it with slow-release fertility . . . .

Bates quoted this article on the topic, which notes the almost enigmatic discovery of this ancient agricultural practice. Biochar was produced and introduced to the soil thousands of years ago producing "Terra Preta:"

Terra Preta ("black earth") was discovered by Dutch soil scientist Wim Sombroek in the 1950's, when he discovered pockets of rich, fertile soil amidst the Amazon rainforest (otherwise known for its poor, thin soils), which he documented in a 1966 book "Amazon Soils". Similar pockets have since been found in other sites in Ecuador and Peru, and also in Western Africa (Benin and Liberia) and the Savannas of South Africa. Carbon dating has shown them to date back between 1,780 and 2,260 years.

Terra preta is found only where people lived - it is an artificial, human-made soil, which originated before the arrival of Europeans in South America. The soil is rich in minerals including phosphorus, calcium, zinc, and manganese - however its most important ingredient is charcoal, the source of terra preta's color.

Terra preta's promised improvement to soils seems almost too good to be true:

This year food shortages, caused in part by the diminishing quantity and quality of the world's soil, have led to riots in Asia, Africa, and Latin America. By 2030, when today's toddlers have toddlers of their own, 8.3 billion people will walk the Earth; to feed them, the UN Food and Agriculture Organization estimates, farmers will have to grow almost 30 percent more grain than they do now. Connoisseurs of human fecklessness will appreciate that even as humankind is ratchetting up its demands on soil, we are destroying it faster than ever before. "Taking the long view, we are running out of dirt," says David R. Montgomery, a geologist at the University of Washington in Seattle.

Journalists sometimes describe unsexy subjects as MEGO: My eyes glaze over. Alas, soil degradation is the essence of MEGO.

Another topic that induces this MEGO phenomenon: Global climate change. And here terra preta steps in and offers an intriguing possibility; low-tech carbon sequestration. After all, these carbon crystals survived for thousands of years in Amazonian and Australian soil. What if this burying of charcoal were revived not only to revive crashing farm yields, but to simply remove carbon from the atmosphere? Bates quotes Tim Flannery:

Professor Tim Flannery told the gathering that even if we shut down every coal plant and stop all emissions of greenhouse gases from industry worldwide, the dangerous warming of our planet would continue for centuries. “That is the point at which you realize that biochar is really, really important,” he said.

Flannery suggested that 8 percent of CO2 is currently going into terrestrial vegetation, but if we could double that, we could buy ourselves time to work on moving away from coal and oil. Flannery said that we have to be mindful of the historic debt incurred by the one billion people whose ancestors made the industrial revolution. “That carbon debt to the other 6 billion could be repaid at 5 percent per year with biochar,” he said. (Emphasis mine.)

And that, as Bates told kmo on the C-Realm, could reverse atmospheric carbon concentrations to pre-industrial levels in a matter of decades, not centuries. And at a fraction of the cost of some proposed schemes.

I'll be reading Bates' new book on the subject as soon as it is available. Fascinating stuff.


Mar. 16th, 2010 11:46 pm (UTC)
While that's all true, if it dries out, it converts into CO2 again.

That's what I thought, but in the podcast interview Bates makes a clarifying distinction between activated charcoal, perhaps the kind you describe, and "inactive" char. I'm not sure what differences need to happen, but he suggests biomass that undergoes a specific type of pyralosis (sp?) crystalizes the carbon char, creating a chemically less active material.

This might be similar to what happens in lead acid batteries. Normally, one has a lead plate (anode) and a lead-oxide plate (cathode) in a dilute sulfuric acid solution. As the battery discharges, the surfaces of both anode and cathode turn into lead sulfide. If the battery isn't charged immediately, however, that lead sulfide crystalizes into lead sulfate, a material which doesn't conduct electricity.

After that point, the battery essentially becomes a boat anchor. That's why lead acid batteries are terrible for electric cars (and were for my electric motorcycles). Think about how just about everyone drives: Go, park, go home, recharge. That eight-hour spell sitting with a partially discharged pack, your batts are slowly crystalizing, slowly destroying their own long-term usefulness. But I digress.

I invite you to listen to kmo and Bates go over the finer points of the process. I'm no expert myself, and await his book's release to become moreso. Oh, and from what I was able to glean, rice hulls can be pyralisized into inert biochar, making the sequestration stretch from 10 years to thousands, while providing fuel for the process.