Zap the trees to reduce carbon

‘Biochar’ pioneers want to put dead plants into a microwave. Why?
Danny Fortson

How do you save the planet? Chop down a tree and put it in a microwave. That’s not a joke. It’s the proposition of at least two dozen companies developing “biochar” technology that they say will suck carbon dioxide out of the atmosphere and help curb global warming.
The idea is straightforward. Trees spend their lives pulling carbon dioxide out of the air. When they die, though, they release it back into the environment. To ensure the carbon contained in the leaves and branches never escapes, trees will be chopped, chipped and put into high-tech “cookers” to reduce them to charcoal, which can then be buried.
In theory the process could be repeated over and over again, fed by giant plantations of fast-growing trees, sucking millions of tonnes of carbon dioxide out of the atmosphere. Chris Goodall, the Green party candidate and author of Ten Technologies to Save the Planet, suggested the world should set aside 200m hectares, an area equivalent to about nine UKs, for such farms. The charcoal could be put down old mine shafts for storage or mixed into soil to enrich it.
The idea is catching on and has the backing of a growing roster of green heavy-hitters, including Nobel peace prize winner Al Gore. James Lovelock, the influential environmentalist, supports its use if limited to plant matter that would otherwise be left to decay. Several firms will test prototypes this year.
Johannes Lehmann, professor of soil fertility management at Cornell University, New York, said it had the potential to remove “a few billion tonnes” of carbon from the atmosphere a year. “This could be one of the top 10 solutions to climate change. It would be irresponsible to not probe its possibilities,” he said. The world generates about 29 billion tonnes of carbon each year.
Some argue the excitement has raced ahead of the science. Almuth Ernsting, who runs the Biofuelwatch blog, said: “There have been no large-scale trials and certainly nothing to prove this actually works.”
Some studies suggest that adding it to soils may activate microbes that break down existing charcoal in the soil, leading to a net increase in atmospheric carbon dioxide.
Doug Parr, chief scientist at Greenpeace, argues that it remains unclear how long CO2 stays contained in biochar and raised concerns over land-use change.
He said: “We need to see further research that’s disconnected from the commercial interests gathering round this. What we don’t want is clear-cutting of old-growth forest.”
Nobody has proposed that. Most speak about using land that is unused or degraded, or feeding in other waste streams such as sewage or agricultural leftovers.
The basic science that holds up charcoal as a stable and reliable carbon sink is, Lehmann said, “absolutely proven”. He added: “Charcoal has been used and produced for millennia by humanity. We need to get away from ideology and let science speak.”
The difference today is how it can be made. The companies developing the technology all rely on the same basic approach. Called pyrolysis, it heats organic material to between 300C and 600C in an oxygen-starved environment. The result is gas, which can be used in a turbine to generate electricity. Depending on the process, the other products are liquids that can be used for fuels or solids like charcoal.
Carbonscape, a New Zealand group, has come up with a variation that uses a patented microwave-assisted pyrolysis process that can zap organic material such as trees and weeds in a matter of minutes.
Chris Turney, the geology professor at Exeter University who invented the system, envisions machines being rolled out all over the world, especially in the tropics, where deforestation is rife. They are made to fit into a standard shipping container and even if powered by coal-fired electricity, Turney said, the machine removes twice the carbon released by the process.
“The whole reason this works is that we could reforest land, harvest it and then reforest again,” he added.
Turney is not alone. Best Energies in America, BIC in Belgium, AnthroTerra in Australia and Agri-Therm of Canada are among those developing rival systems.
The hard fact remains, however, that there is no intrinsic value in incinerating trees and shrubs. None of these biochar pioneers will get far without public money. The most logical way would be to make biochar eligible for the credits that are traded in Europe’s £70 billion carbon trading system. Politicians at last month’s climate summit in Copenhagen proposed its inclusion, as have American legislators.
Meanwhile, biochar has attracted its share of opportunists. Mantria, an American company, was last month charged with fraud after allegedly swindling $30m (£18.5m) from investors, claiming it was the “world’s leading manufacturer and distributor of biochar”.
The Securities and Exchange Commission, the American stock market regulator, said: “Mantria has never sold any biochar and has just one facility testing biochar for possible commercial production.”