The scrubbers, the sulphates and the sunshield solution
Do techno-fixes hold the answer to a climate in crisis? Mick Hamer rides the rollercoaster of hope and desperation.
Green Futures, May/June 2007
In February, Al Gore joined Richard Branson to launch the world’s biggest-ever science and technology prize. The Virgin Earth Challenge is worth $25 million to anyone who can come up with a way of scrubbing carbon dioxide out of the atmosphere.
This isn’t the first time that Branson has tried to tackle global warming with piles of cash. In September last year he pledged to plough the next ten years’ profits from his trains and planes—reckoned to be a cool $3 billion—into developing biofuels.
“Will it work? And do we really need it?”
Cynics will quickly spot the obvious attraction of techno-fixes like these for someone in the airline business. If you could clean up the CO2, there’d be no need to curb the growth in aviation. And if planes weren’t using fossil fuels, they wouldn’t be in the dock as the whipping boys for climate change. Either way, they could carry on flying.
But even if you don’t own an airline, such techno-fixes have a seductive allure. No need for sackcloth and sacrifice, for interminable diplomatic wrangles. With one big neat solution, the problem’s sorted. You can see the appeal when it comes to tackling something as daunting and urgent as climate change. But before we rush to embrace easy answers, we need to ask tough questions.
Do we really need it? Will it work? What about unintended consequences? And is there a better way?
The techno-fix that’s nearest maturity is CCS—carbon capture and sequestration. It’s already being used in experimental power stations, fitted with CO2 scrubbers in their chimneys [see GF63, Can coal come clean?]. Once captured, the gas can be liquefied and pumped into storage—old oil and gas fields are a favoured option for where to put it. The problems here are mainly to do with prohibitive costs per tonne of sequestered carbon—and ensuring the integrity of the storage site.
Better than carbon neutral
Scrubbing CO2 from the atmosphere, however, is a different ball game, says Christian Jardine of the Oxford-based Environmental Change Institute. “Once it’s up there it’s incredibly difficult to do anything about it. The only real hope of success is to use a biological process.”
This, of course, is what plants do—fixing carbon by photosynthesis. So can we dramatically increase the capacity of the planet’s own biological carbon sinks? One idea that generated a lot of excitement was seeding the oceans with iron filings, to stimulate the growth of marine plankton. The algae would take up CO2 from the atmosphere, and the bloom could then be harvested and stored—or left to form corals and sink to the ocean floor. That’s the theory. But experiments have proved disappointing. You do get a bloom, but it dies back or is eaten very quickly—releasing the carbon back into the system.
A less fanciful option, which Jardine agrees should work, is to go back to the idea of the chimney scrubber—but use it to capture the CO2 in biomass-fired power stations. Then your fuel cycle would be better than carbon neutral; it would actually be carbon negative, because you wouldn’t be releasing the CO2 that was sequestered by growing the stuff. “If carbon credits are valued very highly, that would be very profitable,” says Jardine. But the process is unlikely to win Branson’s prize. While there’s still a lot of scope for getting more fuel from woodlands [see Making wood work for plans to do just that in the UK], there are limits on how much biomass we can grow. James Goodman, head of futures at Forum for the Future, makes this point succinctly. “The world’s population is now about 6.8 billion,” he says. “The priority is land to grow more food. Can we grow our own fuel as well? I don’t see it.”
“Living in a greenhouse – with an artificial sunshade to keep it cool.”
Preventing the rise of atmospheric CO2 is not the only game in town for the techno-fixers. Some of the most ambitious schemes involve devising ways of living under denser greenhouse gas conditions—but putting up an artificial sunshade to keep the greenhouse cool. These suggestions range from mirrors in space [see panel below, Angel’s sunshade], to launching hordes of tiny sunlight-reflecting aluminium balloons into the upper atmosphere, filled with hydrogen or helium. Or creating a similar shield with sulphate particles, sprayed up there deliberately to mimic the effect of the dust thrown up by massive volcanic eruptions.
What might that cost? “It won’t be much,” says its champion, the veteran atmospheric chemist and Nobel laureate Paul Crutzen, in a recent interview. “Every citizen of the developed world may have to shell out $25-$50 each to inject enough sulphate particles that can last up to two or three years”. OK, so we’d be living under a cloud…
But this type of ‘geo-engineering’ of the climate is fraught with worse dangers than that. There’s even the worry that blocking out sunlight might work too well. Only a small miscalculation could tip the planet into a new ice age. And hi-tech mistakes do happen. In 1999 the Mars Observer probe crashed into the red planet because NASA mistook imperial units for metric ones.
Concentrated sunshine
Hardly surprising, then, that many remain sceptical. “I get very nervous when we talk about mucking around with the Earth’s atmosphere. That’s how we got into this mess in the first place,” says Forum for the Future’s climate expert, Iain Watt. “I don’t think we have a good enough understanding of how the feedback systems work. We should concentrate on reducing our emissions.”
And how perverse is it anyway, to regard the energy from the sun as the source of the problem? There’s surely more profit in using it to generate emissions-free electricity. Photovoltaic cells (whether the ‘conventional’ or nanotech type) aren’t the only way to do this. An innovative new form of power station—the solar concentrator—even uses mirrors. In this case, however, they’ve got their feet firmly on the ground, where they’re arranged to focus the sun’s rays to boil water—generating the steam to drive a turbine. Sunny Seville is now home to Europe’s first commercial version, using 624 giant movable mirrors. It’s one of a planned series of such plants designed to produce 300MW in the area in the next five years. Researchers estimate that covering 1% of the Sahara—5,000 square km—with these mirrors could generate all the world’s electricity...
“Covering 1% of the Sahara with mirrors could generate all the world’s electricity.”
Jardine has heard this kind of calculation before. “Every few years,” he says, “someone comes up with the idea of using the Sahara for solar power.” But one of the main planks of the UK government’s most recent energy white paper was improving the security of energy supplies. And it might not be the most cunning plan to exchange a dependence on oil from politically unstable countries in the Middle East, to a dependence on solar power from North Africa.
Far better, says Jardine, to go all out for putting PV tiles on the roofs of buildings here in the UK (where we do get at least half the solar radiation per unit area that falls on the Sahara). You’d generate the power where it is going to be used, and avoid the huge transmission losses that would result from bringing it from the Sahara to the national grid. “That implies a microgeneration future,” he says. A future full of PV, wind turbines and combined heat and power—both at the community level and in individual units. They’d supply all the domestic electricity we really need, and a substantial part of the heat for our houses too. The decentralised microgen route does also require some smart technology, of course—but not of the massive geo-engineering all-or-nothing kind.
Not that there’s anything wrong with engineering per se. Where, for instance, would London be without the Thames Barrier? Since it was completed in 1984, the city’s very own anti-flooding techno-fix has actually worked extremely well—on far more occasions than its creators ever expected. Faced with rising sea levels and storm surge threats, the Environment Agency now plans to increase the height of the barrier—and the downstream flood defences. This should keep the capital free from flooding for the rest of the century. But after that the sea is likely to win. “We have just commissioned a study to look at the rise in sea levels which would exceed what we could cope with by simply upgrading the barrier.”
And there, you might say, is a tale that sums up the shortcoming of techno-fix thinking. You focus on tackling symptoms rather than their causes. Your patent remedy may prove effective —for a while. But if the underlying problem is not solved some other way, or does not correct itself, then all you’ve bought is time. Which might be worth it—unless you waste that time.
Angel’s sunshade
The idea of putting mirrors in space to deflect sunlight from the Earth was first proposed in 1989. But the early plans were impossibly futuristic. The mirrors were so heavy they would have had to be manufactured and launched from the moon.
Last year Roger Angel, an astronomer at the University of Arizona, came up with a variant to overcome this launch weight barrier. He proposed launching trillions of tiny spacecraft into orbit, which could cluster together to give the Earth a sunshade. His notional wafer-thin translucent spacecraft, each 60cm in diameter and weighing just one gram, would form a large cylindrical cloud 1.6 million km above the Earth – four times the distance of the Moon. This cloud, he calculates, would cut solar radiation reaching the Earth surface by 2%—enough to offset a substantial increase in the concentration of atmospheric CO2.
Some idea of the Herculean scale of this project can be gleaned from Angel’s own mathematics; creating his sunshade would involve launching four rockets per minute for ten years, each with a payload of thousands of the little spacecraft. And the cost? Perhaps ‘only’ three trillion dollars, if some super-cheap (and completely untested) electromagnetic rocket launching technology were to prove viable. Angel himself is no gung-ho boffin; indeed, he sees his own plan as something we should never have had to contemplate. Nevertheless, its sci-fi appeal seems almost custom-made to catch the imagination of the Bush administration, and he has had some NASA funding to flesh out his idea. And, compared with schemes to mess with the upper atmosphere, it does not have quite the same nightmarish implications for disrupting our planet’s fragile ozone chemistry. |
Fixing the water supply
The lure of the techno-fix is not confined to climate change mitigation. Other audacious ideas try to tackle the problems of adapting to a warmer world, where water scarcity is one critical concern.
China’s water shortage, for instance, has already called forth huge engineering-based projects, not to mention schemes for bringing giant water bags across the seas, and talk of towing emergency icebergs in. The ‘iceberg solution’ has even been mooted for London. Somewhat more plausibly, Thames Water said last year that it was studying the feasibility of shipping fresh water in by tanker—though a wet winter has left the company less keen on that plan. Meanwhile the Environment Agency has ruled out building a national water grid, not only because of its expense—about £11 billion—but because pumping water round the grid would be so energy-intensive. Good to see the thinking getting a little joined up… |
Mick Hamer is a freelance environmental journalist and a consultant to New Scientist.
Last updated:
2008-05-23
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