Enhancing Agriculture and Limiting CO2 With Biochar

The Discovery Science channel ran a series a few months ago called Ecopolis, which discussed a number of promising new technologies that could help citizens of a hypothetical future city deal with critical needs such as energy, food, water, transportation, and waste disposal. Each episode featured four technologies from which Nobel prize-winning energy scientist, Dan Kammen, selected a winner. On the episode entitled A World of Trash, the winner was biochar, a sort of charcoal that can be produced by the pyrolysis of organic materials. Pyrolysis is the process of heating a substance to a high temperature in the absence of oxygen. I recently had the opportunity to attend a biochar presentation called “Biochar 101” given by Lopa Brunjes, Vice President of Biochar Engineering. She did an excellent job in explaining how biochar works and why it’s well positioned to address many issues associated with climate change and fossil fuel depletion.

Biochar’s origins can be traced to South America where natives of the Amazon jungles have been using it for millenia to increase soil fertility. The jungles of South America, despite their lush vegetation, do not have very fertile soil because so many organisms are drawing on it. When jungles are cleared and replaced with crops, the
soil can only produce crops for a few years before becoming depleted. However, the natives of these lands discovered thousands of years ago that if biochar is mixed in with the soil, it can restore its fertility, creating a dark soil known as terra preta. The biochar, which is basically porous charcoal, works in much the same way as a coral reef does in the ocean. Just one gram of biochar can support as much as 500 square meters of surface area. In this porous material microbes can thrive and help to make the soil from 80% to 220% more productive. The biochar helps the soil retain moisture and nutrients and thus can reduce the amount of water and fertilizer required to achieve good plant yield.

Biochar can ctually sequester carbon for several thousand years. Unlike most soil amendments that need to be replenished annually, biochar continues to work its magic for centuries. This has several important ramifications. If carbon stored in trees and other biomass can be taken out of the atmosphere for thousands of years, it can counteract the effect of burning fossil fuels, whose carbon tends to concentrate in the atmosphere. If biomass is simply burned as fuel or otherwise consumed, its carbon ends up back in the atmosphere in a year or two. In addition, biochar can help to make infertile soil capable of producing new biomass, further allowing more carbon to be extracted from the atmosphere. The new biomass can be used to produce more crops, fuel, and biochar in a sort of virtuous cycle. Instead of depleting the soil, it can reverse the trend that modern agriculture has set in motion, which requires massive amounts of fossil fuels like natural gas to be used to make fertilizer to maintain soil fertility.

Biochar isn’t just carbon neutral, it’s carbon negative, and I’ve yet to hear of any technology that sequesters carbon without incurring a significant cost. Instead of requiring a net input of energy, products from the biochar can be used as the fuel to heat the biomass that is being converted to biochar so it’s self-sustaining. In making biochar, the process also produces bio-oil and syngas, a combination of carbon monoxide and methane, and syngas can be reformed using catalysts into other useful products such as liquid fuels like methanol and ethanol. So in addition to making a valuable soil amendment, the process can also produce carbon-neutral transportation fuels.

All societies produce waste biomass, some on massive scales. In America, much of it gets hauled off to be buried in landfills, and produces no further benefit to society. In fact, burying biomass in a landfill actually creates problems because it turns into methane, a greenhouse gas 20 times more potent than CO2, and that ultimately leaks into the atmosphere. That’s why landfills are now required to put in collection wells and draw out the methane so that it can be flared off. However, flaring methane produces no societal benefit. It’s easy to imagine every city having a central repository for yard and agricultural waste that can convert it into useful products like biochar and liquid fuels.

I see a very bright future for this technology. It’s something that can be produced and used locally, and has many benefits with no detrimental effects. Buckminster Fuller liked to remind us that there is no waste, just misplaced resources, and biochar looks like a perfect way to turn organic waste into a valuable resource.