The planet is in trouble. Climate change is already here, and the goal of reducing its magnitude seems difficult to achieve. To reduce greenhouse gas concentrations, some people imagine that technology could provide us with a break, or even a long-term solution. Geo-engineering is exploring possible technical solutions to get rid of excess carbon dioxide (CO2). But is it really possible? A few examples.
1. When carbon dioxide turns to stone
The “simple” way to get rid of carbon dioxide is the one that has been tested at the Hellisheidi geothermal power plant in Iceland with the CarbFix project: mixing carbon dioxide with water and injecting it deep underground into basalt rocks, hoping that time and local conditions will convert all this into minerals.
According to the results obtained, it would take about two years for the metamorphosis to occur. It sounds perfect, but it’s actually very water-intensive, and above all it’s very expensive, almost 25 euros per ton. This is less than other carbon dioxide storage methods, but when we know that we emit more than 30 gigatonnes (30 billion tonnes) of carbon dioxide per year, we are not really giving in to competitiveness.
But as its promoters explain, “CarbFix is not the ultimate solution to climate change, but rather a new tool to combat global warming”, believing that “carbon capture and storage is vital if the world is to limit temperature increases to 2°C”.
The Hellisheidi geothermal power plant in Iceland (Arni Saeberg / CarbFix)
2. Turning pollution… into fuel?
The Goethe University of Frankfurt is coordinating a European project worth two million euros to develop a technology to convert carbon dioxide into fuel. To do this, researchers are using bacteria that convert CO2 and currently produce alcohol (ethanol). But they hope to genetically modify these bacteria so that they eventually use the gases emitted in industrial landfills to transform them into fuels.
Several American universities, including MIT, are studying processes (without bacteria) that also make it possible to transform carbon dioxide into alcohol or hydrocarbons in an industrial way. But we can still wonder about these technologies, because they produce fossil fuels, which in turn will emit greenhouse gases… and pollute our air. Recycled pollution, in a way.
3. Carbon-eating plants
Plants are an ally against global warming because they absorb some of the carbon dioxide from the air, but this is far from enough. If plants were to be used just to remove CO2, some believe that one-third of the world’s arable land would have to be used. Or accelerate deforestation to “recover” new land, with foreseeable consequences on the natural balance.
The team led by Thomas Schwander of the Max Planck Institute for Terrestrial Microbiology (Germany) is taking a different approach: developing synthetic enzymes that would allow plants to absorb more carbon dioxide than they do today. So, can biotechnology be a weapon in the fight against climate change? It will take a lot of experience to find out.
4. Sulphur in the stratosphere
Another way to mitigate the effects of climate change would be to reduce the energy we receive from the Sun. This is the category in which the research of Ulkike Niemeier of the Max Planck Institute for Meteorology (Germany) and Simone Tilmes of the National Center for Atmospheric Research in Boulder (Colorado, USA) have studied the effects of sulphur injection into the stratosphere.
This is somewhat what happens during large volcanic eruptions, when tons of sulphur are thrown very high into the air, and will block solar rays, causing cooling. So could we do the same thing artificially and compensate for man-made warming?
Not so fast, warn the authors, who point out possible side effects (sulphur aerosols could also prevent some of the heat from going into space) and a delicate balance to maintain so that it does not lead to faster warming. Moreover, this method would not change other greenhouse gas effects, such as ocean acidification caused by rising carbon dioxide levels….
5. Limestone in the atmosphere
A team of scientists at Harvard University highlights the risks posed by aerosols containing sulphur (or sulphuric acid), which could damage the ozone layer. They therefore propose to use limestone to do the same work, and thus contribute to reducing the climate risk while neutralizing the acid products that we still dump into the atmosphere and attack the ozone layer. A double beneficial effect, therefore. But we do not know all the effects that this technique could have on the climate, regional or global.
6. A slimming cure for clouds
Ulrike Lohmann and Blaž Gasparini, from the Institute of Atmospheric and Climate Sciences at the Swiss Federal Institute of Technology in Zurich, Switzerland, do not want to change the amount of solar radiation we receive, but to facilitate the cooling of the atmosphere. The Earth reflects some of the radiation it receives from the Sun, and this energy will disperse in space instead of contributing to global warming. However, some of this radiation returned by the planet is stopped by clouds in the upper atmosphere, particularly cirrus clouds.
The two scientists have therefore developed a method to make these famous cirrus clouds thinner, which would then allow more radiation to pass through… and allow a better cooling of the atmosphere. The method is delicate: cirrus clouds “slimmed down” in this way could have a longer life and produce the opposite effect to that desired. Further studies are therefore necessary to properly dose the weight loss cure.
7. The need for global governance
In an article published in Science, Janos Pasztor Cynthia Scharf, Kai-Uwe Schmidt, of the Carnegie Climate Geoengineering Governance Initiative, identified two main types of technologies to reduce the effects of climate change: those that would remove carbon dioxide from the atmosphere, and those that would cool the planet by controlling solar radiation.
The first “should be implemented on very large scales to have the desired effect,” they warn. “Land needs would be immense, impacting overall food prices and food security. Environmental impacts would include biodiversity loss, pesticide pollution and disruption of the ecological balance of the oceans.” As for the latter, applying them without reducing greenhouse gases “would condemn future generations to pursue them for centuries.” In addition, they would present risks to the ozone layer, the climate, ocean acidification…
But for them, the biggest risk in the short term would be the unilateral deployment of solar radiation control technology by an isolated country, a group of countries or even a sufficiently wealthy individual. Hence, according to these authors, there is a need for “global governance” to reduce these risks.