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Why carbon dioxide heats the planet

Some gases in the earth’s atmosphere absorb and then radiate energy, resulting a warming of the earth’s atmosphere. This phenomenon is known as the greenhouse gas effect, and is the primary reason for increasing global temperatures. However, if it did not exist, then much of the earth’s surface would be uninhabitable.

Greenhouse Effect

Radiation from the sun is mainly in the visible and ultraviolet range, which is not absorbed by the molecules in the atmosphere. Some radiation is scattered by particles and clouds, and this doesn’t reach the earth’s surface. The sun heats the earth, and the earth in turn radiates energy, but because it is much cooler than the sun, this radiation is in the infra-red region. Infra-red radiation is absorbed by certain greenhouse gases in the atmosphere. After energy is absorbed, it is radiated in all directions, part of which is back to the earth, thereby heating it.

Greenhouse gases

Water vapour

This is by far the most common greenhouse gas. When it is a gas it has a heating effect, but if it condenses into clouds it reflects the sun away, which has a cooling effect on the earth. The net effect will vary depending on location and weather conditions.

Carbon dioxide

This is the most most significant greenhouse gas. Atmospheric carbon dioxide levels have increased massively since the industrial revolution in the 18th century, when humans started burning fossil fuels on an industrial scale. The levels are unprecedented, as shown by the NASA graph below.

CO2 levels long term

How can we be so sure about historic CO2 levels? The answer is ice cores. Thick layers of ice in Antarctica and Greenland are made up of layer upon layer of compacted snow in which pockets of air are trapped. Analysing the air provides the CO2 level, and the deeper you go, the older it is.

The level of CO2 in the atmosphere is a dynamic process. It increases when fossil fuels are burnt, but some of this will dissolve in the sea, and be absorbed by plants which need it to grow. When plants die they decay and release carbon dioxide. The full interaction is a complex process. However, atmospheric CO2 levels are increasing, and courtesy of the greenhouse effect this will cause average global temperatures to increase.

Methane

The concentration of methane in the atmosphere is much lower than that for carbon dioxide, but it is 21 times more active as a greenhouse gas, which is why excess gas is burnt at oil and gas rigs. Humans are responsible for accidental release during extraction, processing and distribution.

Methane and carbon dioxide are produced in nature when organic matter decays in the absence of oxygen (anaerobic conditions). See biogas. The methane may be released directly into the atmosphere, but much of it has been stored as a methane-hydrate in wetlands, and on the sea bed. This is a massive reservoir, which could be released as global temperatures increase, providing a significant positive feedback. Alternatively, it could be used as a raw material, see our product.

Nitrous oxide

This is present at low levels, but it is a very potent greenhouse gas and is broken down very slowly in the atmosphere. It has the additional harmful effect of scavenging ozone in the stratosphere. It is produced naturally by the action of bacteria and fungi, but human use of nitrogen fertilisers increases this. It is also released from some industrial processes, such as nitric acid and adipic acid production.

Now that safer chemicals are used as propellants and refrigerants, atmospheric levels of CFCs and similar materials are decreasing. These are potent greenhouse gases, and react with ozone in the atmosphere.


Reusing carbon dioxide

An example is Omnagen’s innovative self-powered CO2 converter; a device which converts carbon dioxide, methane and air into useful chemicals, without the need for external energy. This is how the device works.

Carbon dioxide is a very stable molecule, it will react with some minerals to form stable carbonates, but other reactions require energy. Photosynthesis, for example, uses energy from the sun to convert CO2 and water into glucose and oxygen.


Carbon dioxide storage

CO2 is only a problem if it is in the earth’s atmosphere. The greenhouse effect is explained here.

Carbon Capture and Storage (CCS) involves capturing CO2 from the air, or exhaust gases, liquifying it, and then burying it. This is expensive, but it will allow fossil fuels to be used without releasing carbon dioxide into the atmosphere. More details about CCS.