I have a heightened consciousness about diesel buses and 4WDs belching carcinogens because I’ve just finished reading Siddhartha Mukherjee’s excellent book, The Emperor of all Maladies: a Biography of Cancer.
Melbourne’s fleet of 1700 buses is powered almost entirely by diesel engines. Each year they collectively travel around 80 million kilometres, each bus consuming 90 litres of diesel per 100 km. That’s more than 70 million litres p.a. in aggregate.
Melbourne’s taxi fleet, on the other hand, is comprised mainly of LPG powered vehicles. LPG offers a small saving in CO2 emissions compared to diesel (about 10%) but its main advantage is much lower pollution. Compared to ultra-low sulphur diesel, LPG produces less than a fifth as many particles and less than 1% as many ultra-fine particles. It also produces less than one tenth as much oxides of nitrogen (NOx).
One company estimates the cost of converting the engines in the existing bus fleet to LPG at around $55,000 per vehicle. The company says buses that use LPG consume about 100L/100km (about 10% more than diesel buses) but there’s a significant saving in the cost of fuel.
The price of LPG is currently less than half the price of diesel. A bus that covers (say) 100,000 km p.a. would cost $130,500 p.a. in diesel (at today’s price of $1.45 per litre) but only $60,000 p.a. in LPG (at $0.60 per litre). That means the cost of conversion could be recouped within a very short period. This difference depends on factors like distance driven and fluctuations in relative prices. For example, a new excise on LPG of 2.5c a litre comes into effect from July this year, rising to 12.5c over the next four years. On the other hand, the current troubles in the Middle East have increased oil prices.
This highlights another singular advantage of LPG over diesel – it’s less dependent on international price fluctuations. Australia has immense reserves of natural gas from which the propane and butane in LPG are derived. Proponents of LPG also argue that it extends engine life, reduces maintenance and makes buses less noisy.
There appear to be many good reasons for bus operators to shift to LPG so why hasn’t this happened? Read the rest of this entry »