Engineering The Planet

The majority of the world’s scientific community agrees that global climate change is happening. It is the result of mankind’s intensive burning of fossil fuels as a means of getting cheap energy. But it has released billion of tonnes of greenhouse gases, methane and the primarily catalyst CO2 into the atmosphere. If climate model predictions are correct, the planet is in freefall towards a disaster of biblical proportions. But despite apocalyptic predictions, the fact is, human beings will continue to travel in cars and aircraft. And the problem will only get worse as developing nations increasingly demand the same luxuries we have become accustom to in the Western world. Large coal reserves, and the well-developed technology to turn it into power, will continue to play a major role in electrifying rural parts of China and India for the first time. It is unrealistic to expect them, or any other developing country, to stop burning it. But there is a train of thought, known as Geo-engineering, which believes technology can be used to tailor the properties of the Earth to counteract the undesirable effects created by burning fossil fuels. Most of these require either prohibitively expensive engineering in space, are hopelessly impractical, or are liable to have disastrous side effects. However, a competition is under way to find if there is a better alternative, and it may be that there is an easy solution out there that has nobody has thought of. One such brainwave, although rather crude, appears to have merit. It advocates turning CO2 into large dry ice torpedoes. These are then launched into the ocean. At depth they become encrusted with carbon dioxide hydrate making it possible to safely dump large quantities of the stuff without poisoning the oceans. Dropping dry ice in to water has been done at cocktail parties for years. The evaporation gas creates a thin film that actually insulates the substance slowing the process. The result is an interesting smoky effect. But if dry ice enters deep waters it would not turn to gas but rather to a solid carbon dioxide hydrate. This is more stable than methane hydrate, deposits of which have remained stable on the ocean floor, mixed up with mud, for millions of years despite the fact it is less dense than water. Professor Carl Ross from the University of Portsmouth has proposed the idea. Ross is an engineer with a practical and varied background that includes working at Chatham Dockyard, Newcastle University and designing submarines. He says the CO2 could be collected from coal-fired power stations where combustion is initiated with oxygen rather than air. This raises efficiency anyway but also allows effluent gas to be caught so it can be compressed and cooled to form dry ice. Ross proposes shaping the dry ice in to large torpedo shapes so they can be easily launched over the sides of ships in suitable parts of the deep ocean. The density of dry ice is 1.56 times that of water so it will sink, fast. Alternatively, it may only be necessary to liquefy the carbon dioxide and deliver it to the ocean depths in large submarines made with composite hulls. Indeed, Professor Ross has already tentatively started the design and says all this can be done with technology that is already proven and available. The alternatives, as suggested at recently held hearings in the House of Commons Innovation, Universities, Science and Skills Select Committee, are neither practicable nor sensible. Asked about the feasibility of putting space mirrors into orbit, to reflect some of the sun’s insolation back into space, Dr Dan Lunt from the University of Bristol responded that the project would require, “several trillion 60cm mirrors, five times further out that the moon.” The project would also cost, “several trillion dollars.” When he was asked about the possibility of space based sun shades, Dr Lunt said that this too would require trillions of 60cm, “thin disks,” and that if it went wrong, he did not think it would be possible to retrieve them. Dr Brian Iddon, a member of the Innovation, Universities, Science and Skills select committee, responded that: “I would put [the mirrors] in the Sahara Desert to turn water into steam to generate power.” Professor Ken Caldeira from the Carnegie Institution talked a little about his idea of injecting inert dust particles into the stratosphere. He mentioned that others were studying the possibility of constructing high altitude, tethered wind platforms that could be used both to inject particles and generate electric power. He estimated costs of about $1 billion a year and said they could be deployed, “relatively quickly.” But, he feared that there might be unanticipated negative effects. The idea of generating artificial clouds to reflect away the suns heat has been mooted by several academics in recent years along with putting sulphate particles into the atmosphere by adding them to the tail gas of jet engines in airliners. But Dr Vicky Hope from the Met Office warned that its modelling work showed that making favourable changes in one place was liable to cause severe problems in others. Professor Klaus Lackner, from the Earth Institute at the University of Columbia, was questioned over a video-link about his idea for chemical trees to catch CO2, which nobody thought would be bad. But it still left the problem of what do with the CO2 when it was recovered. Other ideas that have been suggested include building earth based solar reflectors on land or on the sea, such as silvered ping-pong balls and polystyrene. However, these would probably not last for long or stay in the right place. And finally the possibility of fertilising the oceans to grow vast blooms of algae, to absorb CO2, has been predicted to likely kill all the fish; as it does in rivers and lakes. Just in case there is another alternative solution that nobody has thought of, the Institution of Mechanical Engineers has initiated a technical project competition for its young members called, “Cooling the planet.” Final judging of this will take place at the ImechE’s London headquarters in March. Pointers * As a substance, CO2 has no liquid state at pressures below 516MPa. At 101MPa it is a solid at temperatures below -78 °C. In this form it is commonly referred to as dry ice. Text: CO2 could be stored in the deep ocean where it will form carbon dioxide hydrate that is extremely stable. It could get there on large submarines or simply by launching large, dry ice torpedoes over the sides of ships Text: The other geo-engineering alternatives, such as space mirrors or doing drastic things to the atmosphere are either prohibitively expensive, hopeless impractical, liable to wreck the environment in some other way, or all three