By John Dunkelgrün
As almost everyone now knows our planet’s climate is changing. Temperatures are rising, weather patterns are becoming less predictable and storms more violent. Arctic ice is melting rapidly, threatening a dramatic rise in the sea level. Droughts, wildfires, hurricanes, and other scourges leave millions of people homeless and hungry.
It is generally accepted that the greenhouse gas emissions of carbon dioxide and methane are the main culprits. Methane is a more potent greenhouse gas, but it doesn’t remain in the atmosphere all that long. CO2 is there for the long haul (see Steven E. Koonin, ‘Unsettled’). To counter this development the main focus today is on reducing the output of CO2.
Depending on whom you talk to we should get to (not just strive towards) halve the emissions by 2030, and stop them altogether by 2050 in order to keep the warming up of our planet to a maximum of 1.5 degrees Celsius. But the climate is already changing under the current concentration of the stuff in the atmosphere and it isn’t going away. Moreover cutting output in ‘the West’ is easily overtaken by growth in countries like China, India, Indonesia etc. So obviously, just slowing down emissions to a full stop some thirty years from now is not enough.
We have to take CO2 back out of the atmosphere. While there appear to be some chemical ways to do that, they haven’t proven that they can be viable on the massive scale required and at present they are prohibitively expensive (Koonin). The best route still seems to let nature do the work, by planting trees or fostering the growth of aquatic organisms that capture CO2.
Planting trees is wonderful. Everyone loves green, but areas with the right soil and water conditions for trees to grow, and that are not already being used for farming, are limited. Yet it is imperative that we find a solution.
Therefore let me take you on a little thought experiment. There are plenty of empty spaces on our planet with enough sun, but hardly any water.
At the same time our planet is awash in water. Over two-thirds of its surface shows blue from space. The problem is that most of it is salty. And while desalination technology is getting better all the time, it is still an expensive and energy-consuming process. But there is hope. Renewable energy by all known technologies is getting cheaper all the time and people all over the world are working on still newer and better methods. It is not at all impossible for abundant renewable energy to become virtually free in the near future.
Norman MacRae, a respected former editor of The Economist, once pointed out that most shortages, once recognised, are turned into surpluses within ten years. And as an example of how dramatically technology and costs can change, in the late sixties the workhorse of computing, the bulky IBM 360/30 computer, had 30K bytes of memory and cost well over $100,000 or not too far from a million dollars in today’s money. And it had just 30 kilobytes of memory, while my current smartphone has 256 gigabytes, almost nine million times as much, and costs about $1,250.
Now assume that in the next few years the cost of energy drops down so dramatically that we can ignore it. Then think about building massive desalination plants financed by the world community. At current prices, it would take about one billion dollars to build a plant that produces one million tons of freshwater per day. Tropical savannas need 100 cm of rainfall per year or 0.275 cm a day. This translates into 2,750 tons of water per km2 per day. That one million tons per day plant produces enough water to turn more than 360,000 km2 of desert into savanna. Build one on either side of Africa (at a fraction of the World Bank annual budget for investment in water projects) and you get enough water to create a swath of 100 km wide from East to West as a green barrier against the encroaching Sahara.
The benefits of this would be stupendous. It could provide work to thousands of Africans planting trees. The growing trees and shrubs would gorge on the carbon dioxide, the herdsmen in the Sahel would have predictable water for their cattle and maize. Perhaps, if the green area would become large enough, it might change the soil and the weather patterns sufficiently so that less desalinated water is needed and can be used to make ever more of the Sahara green.
The desalination of two million cubic meters a day would need about 400 megawatts of electrical power. I have no idea how low the price of renewable energy needs to be for this idea to become viable, but if you look at the cost of the tornadoes, typhoons, droughts, the rising sea level, and hunger relief programs today, it almost seems like a feasible solution at today’s prices. And if this is seen to work in Africa, then the deserts of the Arabian peninsula, the Negev, Chile, and the Gobi could also become our new centers of green, storing the carbon dioxide and feeding the planet, and allowing more food production for the planet’s growing population.
