The threat of nanotechnologically spawned environmental disaster has loomed in the public conscious since 1987, when Eric Drexler described the doomsday "gray goo" scenario in his book "Engines of Creation." In it, self-replicating nanomachines overrun the planet, multiplying exponentially and consuming everything in sight, leaving nothing behind but the titular nanomachine goo [sources: Feder; Drexler].
Since then, more plausible concerns, such as the lack of available information regarding the toxicity and long-term ecological effects of nanoparticles, have dominated the discussion, but there's also a greener way of viewing this tiny technology. Nanotechnology can actually help improve the environment, both by tackling intractable existing problems (called legacy problems) and by engineering sustainable solutions for the future.
Legacy problems are all around us. While the Fukushima Daiichi Nuclear Power Plant radiation leak and other incidents dominate the news, more commonplace remediation challenges face communities daily, from cleaning up former gas stations to tackling the more than 1,500 Superfund sites in the United States alone [source: EPA, "Superfund National Priorities List"].
Nanoscale iron offers one safe approach for neutralizing chlorinated organic solvents, organic chlorine-based pesticides like DDT and polychlorinated biphenyls (PCBs). Add iron nanoparticles to tetrachloroethene (a common solvent used in dry cleaning) and the iron oxidizes, or rusts, freeing up electrons. The reaction gobbles up these electrons, leaving ethene, a naturally occurring hydrocarbon.
Cleanup crews can inject nanoscale iron under pressure into polluted ground, where its small size allows it to be transported in groundwater or left on-site for long-term remediation. Off-site, they are just as useful in slurry reactors or filtration systems. Scientists are currently researching applications for using nanoscale iron to deal with heavy metals and radionuclides as well [source: Zhang].
We may turn to nanotechnology to meet more basic health, food and safety needs, too. For example, nanoscale water filtration systems that transform contaminated, brackish or wastewater into drinking water by pressure-filtering it through pores too small for bacteria or viruses have been in use for more a decade [source: Bradbury].
Now that we've done the cleanup and more, let's look at some of the ways that nanotechnology is making our future greener, too.