CNG: Answer to energy dependence?

Compressed natural gas (CNG) is cheap, clean and metes out the lowest environmental impact of any combustible-fuel alternative available. Like LPG, CNG delivers negligible amounts of sulphur into the atmosphere; sulphur is a significant component in the creation of acid rain.

Further, CNG is safer than LPG, as it requires a very specific concentration to ignite and, being lighter than air, any spills quickly dissipate in the open.
And CNG has a higher "octane" rating than pump petrol.

Finally, burning natural gas (a naturally-occurring by-product in coal-fields) is easier on engines than many other alternative fuels and costs roughly half the price of petrol.

So, in the current economic and environmental 'climate', why are we not jumping on the CNG bandwagon?

Although many service stations now offer LPG, diesel and various octane ratings of petrol, there are almost no commercial outlets for CNG. In fact, as far as vehicles are concerned, there are effectively none -- a couple in Canberra and some planned for Sydney and Melbourne.

At first glance, this would seem to be a death-knell for prospective CNG-powered vehicle development -- except that CNG is the most widely-available energy source besides electricity; many people forget that CNG is piped into millions of Australian homes to operate stoves, hot-water services and -- in southern states -- central heating services too.

So, like the plug-in electric vehicles we hope to see one day, CNG-burning vehicles could be refuelled at home -- with the difference that, thanks to companies such as Mercedes-Benz (and once upon a time Volvo), this alternative technology is here, now.

In practice, a $3000 wall unit is required to compress the gas into a volume one percent of it's original atmospheric volume, and because of the relatively low pressure in domestic systems, refuelling the tanks takes several hours -- much like recharging an electric vehicle.

In commercial applications -- and the Sprinter is primarily a commercial vehicle -- many companies operate forklifts and other equipment burning CNG and will have a large gas storage and refuelling facility on site.

Raw natural gas (before processing) is mainly methane, and may also contain varying levels of ethane, propane, butane, and pentane (commonly called natural gas liquids or NGLs). In its raw state, natural gas may also contain nitrogen, carbon dioxide, hydrogen sulphide and water. Most NGLs, and all these non-energy generating trace elements are removed before the natural gas is pumped into pipelines.

Natural gas from coal, also known as coal-bed methane (CBM), is an almost pure form of natural gas (methane) found in underground coal deposits. Conventional natural gas is produced from sandstones and carbonates. Unlike raw natural gas in conventional underground reservoirs, CBM generally contains very little liquid or non-energy components.

Being a gas, CNG is sold by volume, in cubic metres, whereas LPG, along with other liquid fuels, are sold by the litre. When compressed, a cubic metre of Natural Gas takes up about a litre.

A British Thermal Unit (BTU) is the amount of heat required to raise one pound of water one degree Fahrenheit and is equal to 1.06 kilojoules.
The net energy content of commonly-considered fuels measured as BTUs per pound are as follows:

Petrol: 19,100
LPG: 19,800
CNG: 21,300
Methanol: 8600
Ethanol: 11,500

At current rates of consumption, Australia has at least 170 years of supply of coal-bed methane; it is Australia's most abundant combustible fuel source. In contrast, Australia has only about 10 years of oil reserves.

In addition, chemically very similar biogas is produced naturally from garbage, animal waste and sewage, making these as-yet un-harvested future sources of CNG almost limitless.

Despite this, storage tanks for CNG have much tougher safety standards than LPG cylinders and must withstand various tests, including heat and pressure extremes, fire and even bullets.

Most importantly perhaps, CNG is distributed across most of the major metropolitan areas by a network of underground pipes, unlike petrol and LPG, which are almost entirely transported by road in tankers.

Energy providers in Germany reward the purchase of CNG powered vehicles with direct subsidies or fuel vouchers, and some banks offer attractive credit terms to CNG vehicle purchasers. A number of vehicle insurers also offer environmental discounts. CNG vehicles registered as passenger cars -- for example, the Sprinter crew bus -- are in favourable vehicle tax categories and are therefore much less expensive to operate than diesel vans.

All in all this amounts to an operating cost advantage of up to 30 percent, versus a comparable diesel, and this advantage is even greater in relation to a petrol model.

There are similar programmes in other European countries: Italy has government subsidies and a reduced fuel tax for CNG fleets, while tax-free status is possible in France. Sweden encourages the use of natural gas vehicles with a reduced fuel tax, free parking in inner city areas and exemption from road tolls.
At present there are about 800 gas filling stations in Germany and around 2500 throughout Europe.

It remains to be seen whether Australian governments will have the ticker to encourage the use of clean, cheap, locally available fuel, or continue to support foreign oil companies with endless streams of foreign currency, in exchange for lucrative taxes and levies which provide no benefit to the road transport industry or user.

-- with staff

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