The idea of planting trees to suck CO₂ of the atmosphere as a way of slowing down global warming has been around for years. We even know that planting trees in the tropics would be more helpful than in higher latitudes. But one problem with trees is that we humans tend to cut them down and burn them, and the ones that escape the chainsaws eventually die and decay. Either way, the CO₂ they’ve absorbed ends up back in the atmosphere.

A couple of German scientists have found a solution: plant lots of trees and after a while cut them down and bury them. By entombing the wood in old mines we can keep the CO₂ out of the atmosphere.

Hmm. Carbon buried in the ground. Sounds uncomfortably like fossil fuels. What’s to keep future generations from digging up the wood and, say, burning it?

Another problem is the number of trees we’d need to plant. The scientists estimate that we’d have to plant about 4 million square miles of forest to take up the CO₂ produced in a year. That’s an area about the size of Europe. The scientists note that it’s also about as much virgin forest as we’ve cut down in the last century.

If you’re concerned or even just curious about the health and environmental impacts of nanotechnology, keep an eye on what’s happening around you. The number of consumer products that include nanoscale ingredients has grown from 212 to 609 in a little over two years, a rate of about three and a half per week. Take a look in your pantry, medicine cabinet and garage. If what you see matches any of the products on this list from the Project on Emerging Nanotechnologies, you may be your own best test subject.