South Africa's public transport system may have less of a load to carry if it looks to reduce costs by using compressed natural gas. The country's 380,000 minibus taxi fleet will have the option to convert from petroleum to compressed natural gas (CNG) to help reduce its carbon footprint while transporting about 14-million South Africans every day."We are dealing with the taxi industry and it is difficult to pin them down or get them motivated to fill CNG," said Gerald Ganesh of compressed natural gas company NGV Gas, a subsidiary of CNG Holdings. Despite this, the company manages to fill up 600 vehicles every day at its filling station in Langlaagte, Johannesburg.CNG Holdings has converted 700 vehicles since launching its operations in collaboration with the Industrial Development Corporation last year.story_article_left1"The movement is happening, but it will take quite a few years for these [conversions] to happen," said MD Stephen Rothman. He added that public transport systems were likely to see a gradual movement towards natural gas as the country tried to reduce its carbon footprint.The company was recently awarded a R10-million contract to convert 200 buses belonging to Metrobus - Johannesburg's bus service provider - to use the environmentally friendly fuel, and so reducing costs by 30% to 40%. The buses will operate on a dual fuel model, enabling them to use both diesel and gas, which will be stored in highly pressurised cylinders either in a vehicle's boot or on the roof.Emerging economies in South America and Asia already have greener public transport systems. In Africa, South Africa, Angola and Nigeria are exploring CNG markets.Wrenelle Stander, senior vice-president of public affairs at Sasol, said CNG was an attractive energy source as it was cheaper to buy gas than liquid petroleum fuel.The gas is stored on a vehicle in high-pressure tanks that compress the gas to an air-like state, so that in the event of a gas leakage it dissolves into thin air.The selling price of compressed natural gas is R8.99 per gigajoule, compared with between R10 to R12 per litre for diesel, with one gigajoule of gas equating to 29 litres of fuel.With more than 179-million gigajoules of gas used for commercial and industrial purposes, gas contributes 3% towards the country's diversified energy resources.story_article_right2Sasol is the only energy company that has been able to monetise Mozambican gas by supplying it through a pipeline that runs across both countries to provide gas to 350 customers such as ArcelorMittal SA, Egoli Gas and CNG Holdings.According to Rothman, one of the challenges in providing compressed natural gas is the availability of gas, as Sasol has monopolised its distribution."Sasol is holding on to its gas for obvious reasons, so to really expand that [compressed natural gas] in this country we are going to have to import or develop carbon methane or shale."However, Kribs Govender, vice-president of business development for power and gas at Sasol, said energy sourcing would have to diversify to contribute significantly to power generation."The likelihood of any one being the only option is low - it's how we make sure we get a balanced approach that's important."But South Africa 's limited infrastructure may mean that access to the gaseous fuels will be restricted. "South Africa does not have the infrastructure to run on just gas, it will run on dual [fuel] because you wouldn't necessarily find a [compressed natural gas] filling station in Durban or Cape Town," said NGV Gas's Ganesh...