How do you like the idea of fighting global warming by pumping millions of tons of artificial volcanic ash into the atmosphere to cool the planet? Alternatively, would you support a plan to suspend giant “mirrors” made of fine wire mesh or shiny aluminum nanoparticles in the lower stratosphere to reflect sunlight away from the earth?
If you think these sound like expensive, harebrained schemes rife with the potential for serious unintended consequences, you’re probably right. Yet these and other planet-scaled “geoengineering” programs not only are being proposed, but some are actually being financed and experimented with in England and elsewhere.
Meanwhile, energy companies are continuing to extract fossil fuels from every last crevice of the earth, and conspiring economic and political forces make it unlikely that there will be any serious attempts to reduce greenhouse gas emissions for another generation — by which time it could be too late to prevent the catastrophic overheating of the earth. It increasingly looks like our technocracy will destroy itself, and us in the process.
Or will it?
What if the world’s farmers introduced a simple, inexpensive and earth-friendly agricultural practice that could significantly reduce atmospheric carbon and slow the emissions of the more potent greenhouse gases methane and nitrous oxide? What if that practice produced enough energy to fuel itself, and as an added bonus produced a significant amount or carbon-negative energy in the form of biofuels?
What if it also increased soil fertility by retaining nutrients (while decreasing nutrient runoff, which pollutes natural waterways), built habitat for helpful soil microorganisms, and improved soil stability and tilth — even in some of the world’s poorest soils?
Finally, what if this practice were readily scalable and could be implemented by home gardeners and commercial farmers everywhere — spreading quickly to much of the earth’s arable land to form a giant atmospheric CO2 sequestering system?
In fact, this agricultural practice was introduced over 2,500 years ago by Amazonian peoples who created charcoal from vegetation by “burning” it in an oxygen-restricted environment (pyrolysis) — probably in pits covered with a thin layer of dirt that caused the vegetation to smolder rather than burn outright.
The prehistoric Amazonians then worked that charcoal into the famously poor local soil and added plant nutrients to it, creating arable plots of land called terra preta (black earth). In the 1960s, archeologists working in the Amazon Basin rediscovered these terra preta plots and slowly realized that their original purpose was to make agriculture possible in a region where crops could not grow without soil amendments.
Some terra preta fields that were abandoned at least 500 years ago (with the arrival Europeans in the Amazon basin) remain fertile to this day, proving that buried carbon persists in the soil. (Just as CO2 persists in the atmosphere, which must be “scrubbed” of excess CO2 if we are to slow or reverse global warming. Charcoal, which is close to pure carbon, is essentially inert, and won’t nourish plants, but it helps retain nutrients and supports microbial organisms.)
Research into the properties of terra preta and the benefits of using vegetation-based charcoal — now dubbed “biochar” — along with the pressing need to find solutions to the greenhouse gas problem, have spawned an international movement to promote the use of biochar in agriculture. The excellent web site of the International Biochar Initiative (IBI) serves as a primer in biochar applications and reports on home and industrial-scale biochar production facilities, agricultural research projects and conferences and events worldwide.
The carbon biostorage potential of biochar agricultural practice is the main reason for all the excitement. It works like this: Best practice requires biochar to be made from agricultural and forest waste only, not from plants grown for biochar production. Typically, thirty percent or more of the biomass can be converted to biochar. (The exact figures depend on the nature of the feedstock and the pyrolytic process, the desired ratio of biochar to biofuel in the end product and other factors.)
Once the waste biomass is converted to biochar it’s buried, sequestering its carbon for hundreds or thousands of years. As new plants are grown in the biochar-amended fields, they absorb more CO2, some of which is in turn converted to biochar and buried.
Conservative predictions on the IBI web site establish that biochar agricultural practices can sequester or offset a minimum of one billion tons of carbon per year by 2050 — about 15 percent of our current CO2 output — making it a major tool for controlling climate change.
A slightly different version of this article was published in the nationally syndicated newspaper column “Your Ecological House” (by Philip S. Wenz) in September, 2011.