A few years ago, Ning Zeng began to wonder about the hidden potential of landfill sites. He had been discussing a mystery with his students: for some reason, North America’s carbon dioxide emissions are not quite as high as they “should” be. Perhaps, one student suggested, America’s huge landfill sites were acting as carbon sinks. After all, a lot of what is thrown away does not decompose: even 50-year-old newspapers can be perfectly legible.

Zeng, an atmospheric scientist at the University of Maryland in College Park, later calculated that the amount of carbon sequestered in this way is actually tiny, but it gave him an idea. What if we could sequester the carbon locked up in trees in such a way that it doesn’t get released back into the atmosphere? Could we store enough of it to offset a meaningful amount of emissions?

It sounds like a long shot, but Zeng is convinced it could work. In arecent paper in the journalCarbon Balance and Management (vol 3, p 1), he calculated that if we buried half of the wood that grows each year, in such a way that it didn’t decay, enough CO₂ would be removed from the atmosphere to offset all of our fossil-fuel emissions. It wouldn’t be easy, but Zeng believes it could be done.

Zeng’s is not the only proposal of its kind. Other researchers are totting up the amount of carbon that could be sequestered in various kinds of biomass and are finding that it is a surprisingly large amount. Not enough to halt climate change on its own, perhaps, but enough to make a sizeable dent in atmospheric…