The 103 Metroticket buses that were purchased between March 2000 and May 2002 under Transport SA's bus purchasing contract were powered by Compressed Natural Gas (CNG) rather than diesel fuel.

Advantages of using natural gas are

• lower cost compared to diesel
• lower emissions compared to equivalent diesel buses (especially particulates, NOx, CO and HC when using catalytic converter)
• lower engine noise levels
• use of local fuel resulting in less reliance on imported oil
• reduction in Australia’s trade deficit

CNG buses in South Australia

South Australia has been a pioneer in the use of CNG fuelled buses, the first 10 being converted from diesel in 1988.

A further 100 buses were bought between 1993 to 1996 as original equipment manufacture supplied CNG buses.

When combined with the additional hundred and three gas buses purchased between March 2000 and May 2002, the Metroticket bus fleet is now comprised of two hundred and thirteen CNG buses vehicles which translates to approximately 28%.

Funding

In August 2000 Transport SA received a grant of $1.7 million from the Australian Greenhouse Office granted for the purchase of 103 new Compressed Natural Gas powered buses.

The Australian Greenhouse Office's Alternative Fuels Conversion Program provides a 50% grant for the difference in the purchase price between alternatively and conventionally fuelled vehicles.

While CNG buses cost more than an equivalent diesel bus, cheaper fuel costs and funding from the Australian Greenhouse Office will save Transport SA money over the life of each bus.

Passenger Transport Asset Management Section

The State Government’s buses and bus depots are owned by Transport SA and managed by the Passenger Transport Asset Management Section based at Walkley Heights. It negotiates and manages the leasing of buses and depots to bus service operators on a commercial basis.

The section is responsible for the ongoing viability of the bus fleet, including management of a bus replacement strategy. It also researches and tests technological improvements to ensure that buses provided to bus service operators are environmentally friendly, efficient and cost effective.

CNG Buses now comprise 28.1% of the 730 buses leased to bus service operators.

New Diesel Buses

After May 2002, the second 50 bus contract extension came into effect and deliveries of MAN 18.280NL diesel buses will take place up until June 2003. These diesel buses are manufactured to Euro 3 standard which means in terms of emissions, that the new diesel buses will be considerably better than the older diesel buses operating in the Metroticket bus fleet. It is necessary to invest in diesel buses as they will be used in an area where no gas refuelling facilities exist, and as part of a sensible risk management strategy which aims to balance the exposure of government to variations in the supply of fuel.

The comparison of emissions from the 18.280 NL diesel buses manufactured to Euro 3 standard to the new NL 232 gas buses is shown in the table below in the section on Exhaust gas emissions of Compressed Natural Gas (CNG) compared with diesel.

Biodiesel

A trial of a diesel bus on biofuel has commenced in June 2002, using a 20% blend of bio-diesel with 80% diesel distillate.The trial officially concluded in February 2003 with the vehicle having travelled over 25,000km. Vehicle performance using the 20% blended biofuel was found to be comparable to that on diesel, while exhaust emission testing has demonstrated reductions of over 50% in particulates can be achieved. A final report is currently being prepared to evaluate the use of 20% blended biofuel as an alternative renewable fuel. In addition, a second trial is currently in the planning stages to evaluate using 100% biofuel as a direct replacement for diesel.

Exhaust gas emissions of Compressed Natural Gas (CNG) compared with diesel

As part of a collaborative project between the South Australian State Energy Research Advisory Committee, the Passenger Transport Board and the Transport Systems Centre from the University of South Australia, Transport SA is currently evaluating the performance of the MAN NL 202 CNG and NL 202 Diesel buses. With the required data collection and emissions modelling now complete the Transport Systems Centre is currently in the process of analysing the results and producing a final report.

Exhaust gas emissions are lower from natural gas engines than diesel engines. Data supplied by the bus manufacturer indicates that compared to our current diesel buses, each natural gas bus emits approximately

• 80% less carbon monoxide
• 59% less hydrocarbons
• 89% less nitrogen oxide
• 95% less particulate matter
• with 50% less noise.

Emissions from vehicles are required to meet international standards. As shown in the table below, emissions of carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx) and particulates (PM) are significantly lower than the current Euro 3 emissions limit specifications, which came into effect as of 1 January 2002.

In fact the emission levels produced are more comparable with those required within the 2005 Euro 4 requirements.

/kWhr is grams per kilowatt hour

{For the technically minded, the NL202 CNG bus is fitted with a MAN E2866 DUH natural gas engine. It is a dedicated, normally aspirated gas engine, operating under a stoichiometric air/fuel ratio. The engine has closed loop technology and is fitted with a three-way catalytic converter.}