Worldchanging guest writers David Zaks and Chad Monfreda are graduate research assistants at the Center for Sustainability and the Global Environment at UW-Madison where they study how human activities affect our planet.

We live on the Blue Planet, but 97% of Earth's water lies in the oceans. Salt water can neither be drunk nor used for farming. Therefore, a cheap, efficient method to turn seawater into freshwater is something of a holy grail in water planning, offering as it would the means to help alleviate water scarcity. Current desalination methods, though, are either energy intensive and expensive, or (like the Watercone or fogcatchers) only workable on small scales.

That may be about to change. A team of researchers at the Lawrence Livermore National Laboratory recently published a paper (subscription required, companion paper) in Science detailing a method to produce carbon nanotube membranes that could reduce the cost of desalination by 75%. As Technology Review reports:

The carbon nanotubes used by the researchers are sheets of carbon atoms rolled so tightly that only seven water molecules can fit across their diameter. Their small size makes them good candidates for separating molecules. And, despite their diminutive dimensions, these nanopores allow water to flow at the same rate as pores considerably larger, reducing the amount of pressure needed to force water through, and potentially saving energy and costs compared to reverse osmosis using conventional membranes.

Both liquids and gases flow through the carbon nanotubes at rates thousands of times greater than in conventional polycarbonate membranes. If the nanotube membranes can effectively separate salt from water, they might also be useful for removing CO2 and other pollutants from flue gases. The researchers anticipate that it will take five to ten years before the technology will be ready for the market. Innovations like this show that while some applications in nanotechnology like molecular manufacturing are decades off, others are almost ready to change the world.