Climate change fighter spills the dirt on biochar

It’s safe to say that biochar is a miracle.

It doesn’t look like much. Just a handful of dirt. But this innocuous black mound is actually the perfect marriage of nature and science.

It acts like fertilizer in healthy soil, adds nutrients back into depleted soil, and even combats climate change by pulling carbon out of the air and putting it back into the earth where it belongs. It can be used on any garden or lawn and can help plants weather or recover from drought.

“I learned about biochar five years ago,” said Debbie Cook, who was working as the greenscapes manager for the North and South Rivers Watershed Association at the time. She’d been researching environmentally-friendly methods of lawn care, but what she actually found was even bigger and better.

“I thought, ‘It can’t be this good,’” said Cook. “It’s a true miracle. I’m obsessed.”

Which is how she found herself in Peru at the Sachamama Center for Biocultural Regeneration, making and sharing biochar with Kechwa farmers whose slash-and-burn-style agriculture was depleting soil beyond the point of recovery.

Cook met Frederique Apffel-Marglin, a Smith College professor of anthropology, at a potluck dinner in Cambridge, where the professor told her about a Peru service trip she would be leading. Cook knew right away that she had to go. She didn’t know who else was going or where they would stay, but it didn’t matter; she had to learn more about this miracle substance.

It was Cook and 16 others, most of them millennials – students of Apffel-Marglin or her daughter, who is also a professor. Despite their generational differences, Cook said everyone got along well, had fun, and learned a lot.

Over the course of six weeks, the team built special stoves in four villages in the region. The ovens heat organic material to a high temperature without oxygen through a process called pyrolysis; this is the key to creating biochar.

 The result is a porous, inert carbon, which has lots of room for storing vitamins, minerals, and moisture for plants to use as they need it – as well as for all that extra carbon that’s been hanging around the atmosphere, pushing global temperatures ever higher.

“I call it a condominium or house for microbes and water,” Cook said.

With the stoves in place, the team taught the Kechwas how to use them. This variety of biochar was called “Terra Preta” and included microbes from the forest floor, cow manure, nuts, and coconut shells.

Making Terra Preta is an involved process that requires an investment of time and effort from everyone in the community. But the investment pays off within a year, when gardens that have lain fallow for generations are suddenly – miraculously – able to produce vegetables again.

If biochar catches on in the region, it could herald a marked improvement in quality of life for the Kechwas. Because the tribe has been practicing slash-and-burn agriculture for so long, they have to travel further and further from their homes to reach their farms and gardens, sometimes as far as six hours away – and there’s no fast or easy means of transportation.

The irony is that biochar originated in the Amazon. Cook cited Charles C. Mann’s book “1491: New Revelations of the Americas Before Columbus,” which says that a substance like biochar was once widely used in that area.

Researchers today are unsure exactly what went into this ancient recipe, but they know it sustained millions of people along the Amazon, a region whose soil is today considered too poor to support such a population. One ingredient would have been fermented human waste, because the indigenous people did not keep farm animals whose manure could be used.

When European explorers brought smallpox to the Amazon, millions died, and with them went the knowledge of biochar. There were not enough people left to continue making it, and that’s when the people turned to slash-and-burn agriculture using steel and machetes brought by explorers.

The new method could completely deplete a plot of soil within two years. Now, with the rediscovery of biochar, that same soil can be fully replenished in the same amount of time.

Cook used biochar in her own garden this summer and said that, despite the drought, her chives and lavender doubled in size. A contact of hers, Bob Wells, who makes and sells biochar ovens all over the world, uses it on his sandy Cape Cod property and now regularly wins the Eastham turnip festival.

If you’re looking for the inevitable downside of biochar, so far, it’s only this: biochar must be “charged” before use by leaving it to sit in compost for two weeks. Otherwise, especially if you use it on your lawn, it will start grabbing up all the nearest microbes – the ones that are in the plants. Biochar needs to be fully loaded with microbes before application.

It’s worth the effort, if you ask Cook and other proponents.

“If we’re going to keep our climate habitable, we need less than 350 parts per million of carbon dioxide in the atmosphere. Last week, we exceeded 400,” Cook said, quoting national climate leader Bill McKibben of is building a global climate movement through online campaigns, grassroots organizing, and mass public actions, coordinated by a global network active in over 188 countries.

 “The only reason we’ve escaped for now is that the oceans have sequestered carbon dioxide,” Cook went on, “but it’s making the oceans acidic; it will eat the shells of lobsters.”

That’s why she couldn’t stop with Peru. In November, Cook and Apffel-Marglin are going to Morocco to introduce this new form of agriculture at the Marrakech Climate Change Conference. They’re preparing a TED-style talk, which Cook would be thrilled to share with other audiences.

To inquire about Cook’s presentation, or to try our biochar for yourself, contact Debbie Cook at

This story originally appeared in the Cohasset Mariner.


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