A pedestrian view

29/04/2000

A pedestrian view THE great compressed natural gas (CNG)-diesel debate has touched new, abysmal levels of absurdity! Consider the choice before us. On the one hand we have the noisy, foul-smelling, poison-belching diesel engines that choke our cities and their citizenry in noxious fumes and clouds of suspended particulate matter. On the other, we have the CNG engines: relative newcomers to the scene, quieter and far less smoky than their diesel-burning brethren, yet damned as environmentally unsound by the diesel lobby because they contribute to global warming! Absurd indeed.

Certainly there's no disputing the fact that CNG contains hydrocarbons such as methane - a well-known greenhouse gas - whose combustion produces carbon monoxide and carbon dioxide. The latter, too, is a greenhouse gas. In addition, carbon monoxide has the potential to destroy the Earth's ozone layer, which in the long run will allow more solar ultraviolet radiation to penetrate into the atmosphere and thereby hasten the advent of global warming. (Diesel burning, too, produces oxides of carbon, but in far less quantities than CNG). On the face of it, therefore, it would appear that diesel is definitely more environment-friendly than CNG.

But wait a minute! There is another aspect to the issue: the question of our very survival! Diesel exhaust contains enormous quantities of incredibly-fine carbon particles that are coated with the most deadly cocktails of organic and inorganic poisons-prominent among these are polycyclic aromatic hydrocarbons (known as carcinogens) and sulphates of heavy metals. The smaller these particles, the greater their overall surface area, and hence, the larger the number of toxic molecules that can cling to their surfaces. Also, the smaller the particles, the deeper they can penetrate into our bronchial tubes and lungs to deliver their lethal cargoes.

We must also view the diesel lobby's concern for the environment in proper perspective. If, as they point out, CNG is harmful because it contributes to the greenhouse effect and global warming, there is another substance, commonly found in the Earth's atmosphere, whose greenhouse potential is far greater than CNG or its derivatives: namely, water vapour! The diesel lobby might well argue, therefore, that vehicles that run on fuel cells - considered to be among the cleanest of energy technologies - will be even more damaging to the environment than CNG engines, because fuel cells derive their energy from the exothermic reaction of hydrogen and oxygen, and their exhausts comprise nothing but water vapour!

Quite ridiculous, of course.

In the light of all this, the choice before us becomes clearer. On the one hand, we can drive smoother, quieter and less smoky cng cars while grieving over the fact that in the long term we are contributing to global warming. On the other hand, we could race around in our diesel cars, choking to death in the near term even as we rejoice in the knowledge that our vehicles - and indeed our own extinction - will not contribute greatly to global warming.

Perhaps there is a third option, though...till better ways are found to tap wind and solar energy, we could walk and cycle more.

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