Can nanotechnology really be green?

This essay was first published in Nature Nanotechnology, February 2007, Volume 2 No 2 pp71-72 (doi:10.1038/nnano.2007.12), abstract here.

In discussions of the possibility of a public backlash against nanotechnology, the comparison that is always made is with the European reaction against agricultural bionanotechnology. “Will nanotechnology turn out to be the new GM?” is an omnipresent question; for nanotechnology proponents a nagging worry, and for opponents a source of hope. Yet, up to now, there’s one important difference – the major campaigning groups – most notably Greenpeace – have so far resisted taking an unequivocal stance against nanotechnology. The reason for this isn’t a sudden outbreak of harmony between environmental groups and the multinationals that are most likely to bring nanotechnology to market in a big way. Instead, it’s a measure of the force of the argument that nanotechnology may lead to new opportunities for sustainable development. Even the most vocal outright opponent of nanotechnology – the small Canada-based group ETC – has recently conceded that nanotechnology might have a role to play in the developing world. Is nanotechnology really going to be the first new technology that big business and the environmental movement can unite behind, or is this the most successful example yet of a greenwash from global techno-science?

The selling points of nanotechnology for the sustainability movement are easily stated. In the lead are the prospects of nano-enabled clean energy and clean water, with some vaguer and more general notions of nanotechnology facilitating cleaner and more sustainable modes of production sitting in the background. On the first issue, many people have argued – perhaps most persuasively the late Richard Smalley – that nanotechnology of a fairly incremental kind has the potential to make a disruptive change to our energy economy. For example, we’re currently seeing rapid growth in solar energy. But the contribution that conventional solar cells can make to our total energy economy is currently limited, not by the total energy supplied by the sun, but by our ability to scale up production of photovoltaics to the massive areas that would be needed to make a real impact. A number of new and promising nano-enabled photovoltaic technologies are positioning themselves to contribute, not by competing with existing solar cells on conversion efficiency, but by their potential for being cheap to produce in very large areas. Meanwhile, as the availability of clean, affordable water becomes more of a problem in many parts of the world, nanotechnology also holds promise. Better control of the nanoscale structure of separation membranes, and surface treatments to prevent fouling, all have the potential to increase the effectiveness and lower the price of water purification.

How can we distinguish between the promises that come so easily in grant applications and press releases, and the true potential that these technologies might have for sustainable development? We need to consider both technical possibilities and the socio-economic realities.

Academic scientists often underestimate the formidable technical obstacles standing in the way of the large scale scale-up of promising laboratory innovations. In the case of alternative, nano-enabled photovoltaics, difficulties with lifetime and stability are still problematic, while many processing issues remain to be ironed out before large scale production can take place. But one reason for optimism is simply the wide variety of possible approaches being tried. One has polymer-based photovoltaics, in which optimal control of self-assembled nanoscale structure could lead to efficient solar cells being printed in very large areas, photochemical cells using dye-sensitised nanoparticles (Grätzel cells) and other hybrid designs involving semi-conductor nanoparticles, or III-V semiconductor heterojunction cells in combination with large area solar concentrators. Surely, one might hope, at least one of these approaches might bear fruit.

The socio-economic realities may prove to be more intractable, at least in some cases. The think-tank Demos, together with the charity Practical Action, recently organised a public engagement event about the possible applications of nanotechnology to clean water in Zimbabwe, which emphasised how remote some of these discussions are from the real problems of poor communities. In the words of Demos’s Jack Stilgoe, “The gulf between Western technoscience and applications for poor communities is far wider than I’d imagined. Ask people what they want from new technologies and they talk about the rope and washer pump, which would stop things (like snakes) falling into their wells.” It’s clear that for nanotechnology to have a real impact in the developing world, a good understanding of local contexts will be vital.

Perhaps, in addition to these promises of direct solutions to sustainability problems, there are some deeper currents here. Given the emphasis that has been given by many writers to the importance of learning from nature in nanotechnology, it’s perhaps not surprising that we’re seeing this idea of nanotechnology as being derived from natural sources, and thus intrinsically benign, cropping up as an important framing device. Referring to the water-repellency of nanostructured surfaces as the “lotus leaf effect” is perhaps the most effective example, both lending itself to comforting imagery and connecting with the long-established symbolism of the lotus leaf as intrinsically, and naturally, spotless and stain-free.

Whatever these deeper cultural contexts, nanotechnology certainly finds itself in the frontline of another important shift, this time in science funding policies. In many countries, the UK included, we’re seeing a shift in emphasis in the aims of publicly funded science, away from narrowly discipline-based objectives, and towards goals defined through societal needs, and in particular towards mitigating global problems such as climate change. As an intrinsically multidisciplinary, and naturally goal-oriented, enterprise, nanotechnology fits very naturally into this new framework and applications of nanotechnology addressing sustainability issues will certainly see increasing emphasis.

Sceptics may see this as just another example of a misguided search for technical fixes for problems that are ultimately socio-political in origin. It may be true that in the past such an approach has simply led to further problems, but nonetheless I strongly believe that we currently have no choice but to continue to look to technological progress to help ameliorate our most pressing difficulties. The “deep green” school may argue that our problems would be cured by abandoning our technological civilisation and returning to simpler ways, but this view utterly fails to recognise the degree to which supporting the earth’s current and projected population levels depends on advanced technology and in particular on intensive energy use. We are existentially dependent on technology, but we know that the technology we have is not sustainable. Green nanotechnology, then, is not just a convenient slogan but an inescapable necessity