Carbon sequestration — taking CO2 out of the atmosphere, as opposed to merely not adding to it — is the thing that will fix the mess we’ve created. Avoiding emissions is all well and good, and will ensure that things get back to how they should be, eventually. But wouldn’t it be a good idea to help things along a little?
There have been lots of suggestions about how we might be able to draw CO2 back out of the sky. Solutions range from the mechanical (e.g. the fabled carbon capture and storage beloved of coal-firing power companies), through the chemical (like iron enrichment of the oceans to promote blooming of carbon-storing algae) to the biological (such as our favourite, planting trees).
One idea that keeps bubbling back up to the surface, as it were, is the idea of burying carbon. Writing last year in the journal Carbon Balance and Management, University of Maryland climate scientist Ning Zeng estimated that around 10 gigatonnes of carbon could be sequestered each year by burying dead trees. To put that in context, the annual greenhouse gas emissions from burning fossil fuels is around eight gigatonnes. The scale of the required operation is vast.
So vast, in fact, that climate changing carbon burial seems like nothing more than a fanciful thought experiment.
But then dreams can be powerful things. Enter James Lovelock, veteran scientist-campaigner who has had more than his fair share. His proposals on how to address climate change have meandered over the years among calling for more nuclear power, pumping cold water from the ocean depths, and even abandoning all hope of saving civilization as we know it.
Lovelock’s latest technofix — what he calls our last chance to save mankind — is a variation on the tree burying plot. By turning as much biomass as possible into charcoal — biochar — and then ploughing it into the soil, we can “cheat” decomposing bacteria out of their fill, thus making sure the carbon stays in the ground rather than finding its way into the atmosphere. But perhaps the science won’t uphold the dream.
The idea might just die back down again, but then this was published recently too. Writing in Environmental Science and Technology, Stuart Strand and George Bedford describe how they think it should be done: large amounts of agricultural crop waste — such as maize stalks and wheat straw — should be bundled up, shipped out to sea and sunk to the deepest depths of Davy Jones’ locker.
Burying such huge amounts of carbon seems both ludicrous and ridiculously simple at the same time. On one hand, it is theoretically possible and appears to make economic sense. On the other, the unimaginable quantities involved, and the transport infrastructure needed to make the dream a reality, seem insurmountable. Yet there remains that nagging feeling that digging for victory has already worked once before.