During the 1980s and 90s Australia’s state and territory governments began investing in compressed natural gas (CNG) buses in an effort to reduce the emissions impact of their public transport systems. CNG has low particle emissions because of its low carbon to hydrogen ratio, which also results in the production of less carbon dioxide per gigajoule of fuel than diesel. However in 2010, improvements in clean diesel technology, lack of CNG re-fuelling infrastructure, and high maintenance costs are forcing governments to reconsider purchases of CNG-powered vehicles.

2010 snapshot

In 2010 CNG buses are contributing to lower tailpipe emissions in the majority of Australia’s capital cities.

Western Australia’s Public Transport Authority is continuing to invest in CNG buses in Perth adding a further 80 CNG buses during the 2009–10 financial year to its 444 strong fleet, and another 74 CNG buses in 2010–11.

The South Australian Government currently exceeds its 25 per cent target of CNG buses with 204 CNG vehicles in the Adelaide fleet, and ACT’s 70 CNG buses comprise 17 per cent of the territory’s fleet.

NSW State Transit operates five bus depots with onsite CNG re-fuelling stations to cater for its 571 CNG buses in Sydney and out of Brisbane City Council’s 930 buses, one third are powered by CNG.

CNG roadblocks

Losing the green advantage?

The development of ultra-layered sulphur fuel and associated engine technology has narrowed the gap between CNG and diesel in terms of meeting Australia’s national motor vehicle standards.

A spokesperson for the South Australian Department of Transport said that when the department introduced the first ten CNG buses to the state’s fleet in 1984, CNG vehicles boasted a clear environmental advantage compared with diesel fuels.

However, in September, 2009 ACT Chief Minister and Minister for Transport John Stanhope told the ACT Legislative Assembly “CNG is no longer the cleanest fuel, with clean diesel a competitive alternative.”

His comments came as the ACT Government unveiled the first of 74 MAN Euro 5 diesel buses as part of the Government’s $49.5 million bus replacement program for the ACTION fleet.

Down to business

In 2004 at the launch of Brisbane City Council’s 150th Australian-made, CNG-powered bus, Brisbane’s Lord Mayor Campbell Newman found the business case for using natural gas buses “compelling”. However, a lack of availability of gas in some Brisbane depots has led to the purchase of diesel buses.

Other states are concerned about the cost of refuelling infrastructure and higher maintenance costs in the face of diminishing Federal Government CNG fuel rebates.

Both South Australian Department of Transport and NSW State Transit spokespersons indicated that CNG buses incur higher maintenance costs than their diesel counterparts as they operate at higher temperatures.

The case for CNG

While there remain some concerns regarding the cost-effectiveness of CNG-fuelled public transport systems, the long-term benefits of increasing the proportion of CNG vehicles in state-owned fleets are being considered by public transport authorities.

A NSW State Transit spokesperson said that a CNG-powered bus fleet decreases dependence upon diesel fossil fuel as the concept of peak oil starts impacting fuel pricing.

CNG bus manufacturer Scania National Bus and Coach Manager Trevor O’Brien said the company is about to begin a factory supported field trial of its third generation CNG engine and “well and truly” believes there is a future for CNG as a fuel source.

Mr O’Brien said “Australia, with its abundance of natural gas, has the unique opportunity to use this indigenous fuel for many and varied applications, buses being one of them.”