Bio-fuels might hold the key to stopping global warming

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

20 December 2009

Why is there so much talk about global warming? Well; simply because the average temperature of our planet has been rising gradually over the last 100 or so years. Scientists have identified the culprit responsible for this as increased levels of carbon dioxide in the atmosphere.

Now, the atmosphere comprises mainly of nitrogen (about 78 per cent), oxygen (21 per cent), argon (0.9 per cent), carbon dioxide (0.04 per cent) and smaller amounts of other gases.  The total mass of all this air around the planet is about 5 million billion tonnes, thus the carbon dioxide weighs about 200 billion tonnes only.

Emissions from fuels add about 30 million tonnes of carbon dioxide to the atmosphere. Now that’s a small amount compared 200 billion total; but it is enough to cause worry. If this situation continues for 100 years, the total amount will rise by 3 billion tonnes – about 1.5 per cent.

Now carbon dioxide is not a bad thing. Together with the other gases, it helps keep our planet warm and habitable. In fact, if there were no atmosphere, the earth would be a very cold place. The intensity of solar radiation is about 1,000 watts per square metre. Any object is heated at that rate would maintain a stable temperature of negative 20 degrees Celsius and that would be inhabitable.

The problem is that carbon dioxide is a very poor conductor of heat. It has about half the conductivity of Nitrogen. Secondly, it is heavier than most naturally occurring gases, therefore it remains mainly in the lower atmosphere (it is one of the reasons why carbon dioxide is used in fire extinguishers).

These two properties make this gas a very good “blanket” around the earth. Thus increasing its quantity in the atmosphere raises the average temperature of our planet by a big amount.

“Big” here means about a degree or so, but it has catastrophic effects on the planet. For example, ice melts at zero degrees Celsius. Increasing the average temperature by one degree will melt naturally occurring ice and the water thus formed will flow to the oceans; sea levels rise and many islands are submerged.

This is not a simple problem and simply reducing carbon dioxide in the atmosphere might not be a permanent solution. The process of extracting energy by chemical reaction (for example, burning a fuel) always produces a gas as an exhaust. This is a basic law of nature.

Thus even if we were to get an alternative fuel to replace oil, we would still have to deal with global warming because of the increased mass of the atmosphere. An increase of any gas will increase the size of the atmospheric blanket and therefore raise global temperatures.

But firewood might hold the key. The reason is that a tree absorbs carbon dioxide while growing and the releases it when burned. It is no wonder that there has been so much interest in biofuels in recent years.