Dublin Bus has decided against converting its fleet to gas although a three-year study showed the move would produce less exhaust and noise emissions than diesel engines.
The company has decided instead to convert to an ultra-low sulphur diesel engine which it claims was found to be more reliable. The company is converting its fleet to use the low-sulphur diesel at a cost of about £1 million. Iarnrod Eireann and Bus Eireann also expect to be using the new fuel next year.
The diesel engines currently used by Dublin Bus are associated with high emission levels relative to other fuels, particularly in particulates (PMS) and visible smoke.
The company undertook trials using buses powered by Compressed Natural Gas (CNG) and Liquid Petroleum Gas (LPG) and said it found both fuels produced less emissions than diesel.
However, the company found the gap between emissions from gas and diesel engines "would appear to be narrowing due to improvements in diesel technology" while the CNG vehicles in particular proved less reliable. It concluded that conversion of existing vehicles to gas power "was not a viable option due to financial, reliability and safety implications".
New gas-powered buses are between 20 and 30 per cent more expensive and between 30 and 50 per cent more expensive to run than diesel buses, the company maintained.
The company said: "Dublin Bus consumes only a small percentage of the fossil fuel used in the Greater Dublin Area with only 1,100 vehicles in its fleet, and far greater reductions can be achieved by targeting other sources of pollutants."
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