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Some fuel for thought

26 March 2013 - 04:12 By Crispian Olver
Crispian Olver
Crispian Olver

Using natural gas to run vehicles always struck me as a bit impractical. For one thing, it is highly flammable, with a likelihood, in our accident-prone society, of vehicles exploding across our littered streets.

 Secondly, South Africa doesn't have a substantial source of natural gas, unless we frack the Karoo. Then there's the cost of storage and distribution to make gas readily available at petrol stations.

But take India's Delhi. Though it is a sprawling city with perennial traffic jams and heavy air pollution, it has embraced compressed natural gas as a cleaner-burning fuel compared with petrol. In the interests of public health, the Indian Supreme Court even decreed that all taxis and buses have to be converted to CNG.

Today the city has a well-established gas infrastructure that delivers CNG to more than 100000 vehicles.

Worldwide, there are now more than 12 million natural gas-powered vehicles in use , more than half of which are in the Asia-Pacific region and another quarter in Latin America.

Another breakthrough has been the use of organic waste and sewage to produce gas. Some cities have been able to power their vehicles entirely off biogas. A recent South African study estimates that organic waste from the country's households could power 7100 buses, while biogas from waste water treatment plants could run another 13200 buses.

So why aren't we moving on to natural gas?

I checked out the safety issue, and was surprised to discover that natural gas-powered vehicles are at least as safe as, or safer than, conventional cars. That is because of the properties of the fuel itself and the integrity of the gas storage and delivery system.

Natural gas is non-toxic and, if it spills, it doesn't contaminate soil or water. When mixed with air, it needs a particular concentration to burn. Also, gas cylinders are much thicker and stronger than petrol tanks, and are designed not to rupture.

Some South African cities have been looking into the feasibility of moving bus fleets on to natural gas. Fleet trials conducted by the Industrial Development Corporation are positive, showing an increase in efficiency and a decrease in engine wear. There are also start-up biogas facilities which are producing gas on a commercial scale.

Despite a slow start, it seems we are on the verge of a big shift towards a biogas economy.