Carbon Footprint of Car Travel

200 grammes per passenger kilometer

“At 0.85 kg of CO2 per kilometer, air travel produces by far the largest amount of GHG emissions per passenger kilometer of any form of transportation. By comparison, a single-occupant vehicle produces 0.20 kg of CO2 per kilometer, and a bus produces 0.07 kg of CO2 per kilometer.”

Source2: “Heat” by George Mombiot , (Penguin 2006) (He gives other references)

p146. Quotes 1.56 passengers per car. that would be 128 gm C02e per passenger.

Source3: http://carboncalculator.direct.gov.uk/index.html

Answers in kg co2

1000 Mj Electricity – 119
1000 Mj Gas – 53
1000 litres oil – 2690
1000 litres lpg – 1490
1000 kg coal – 2548

1000 km smallfamily car – 175 kg

Source3: http://www.ptua.org.au/myths/energy.shtml

Embodied Energy

The manufacture of vehicles uses substantial amounts of energy, and this should be taken into account when assessing the efficiency of various modes of transport. The following calculations are based on the estimate that to manufacture 1kg of metal, plastic and other raw material for vehicles requires 100MJ of energy. Figures comparable to this are found in many sources, including the RTA study mentioned above.

A small car weighing 1 tonne uses 100GJ of energy; if driven a generous 200,000km in its lifetime this corresponds to 0.5MJ per km. Large four-wheel-drives weigh up to 2 tonnes and increase the manufacturing energy in proportion. On the whole, the tendency since the 1970s has been for cars to get larger.

In general, only 75% of the Carbon Dioxide emissions associated with the entire life cycle of a car is from it’s every day use. 19% is the Carbon Dioxide emitted from the production of fuel, 6% from the extraction of the raw materials used on the car and the remaining 2% in the cars assembly. (http://earthtrends.wri.org/features/view_feature.php?theme=5&fid=53)

The energy in manufacturing a 200 tonne train appears daunting at first: 20 terajoules (20 million megajoules). But this train will, conservatively, travel an average 300 to 400km in service each day over a lifetime of 30 years. Thus it will have provided around 4,000,000km of service before going on the scrapheap. On a per-kilometre basis, then, the seemingly large energy requirement comes down to just 5MJ per km. Dividing by mean patronage of between 500 and 1200 passengers gives the very small figures seen in the table.

Similar reasoning applies to buses and trams. Both will typically do about 50,000km in service each year. Trams are of course a good deal heavier than buses – buses weigh 10 to 15 tonnes, while trams weigh 30 to 50 tonnes – but this is counteracted by the difference in operating lifetime. When Melbourne’s W-class trams were retired (for specious reasons) in 2001, the newest of them was around 50 years old, and the oldest about 70 years old. Conservatively, then, we estimate tram lifetime as between 30 and 50 years. Buses on the other hand have an operating lifetime of 10 to 20 years, similar to cars. Thus the embodied energy works out about the same for each when the effect of greater embodied mass is balanced against that of longer life.

A ‘light’ 250cc motorbike has a mass of around 100kg. Based on a (fairly generous) 100,000km driving life this gives embodied energy of 0.2MJ per km. A 1000cc bike has a mass closer to 250kg, and so the upper estimate is scaled accordingly.

Indicative figures for bicycles are 15kg mass and 20,000km ridden in the bicycle’s lifetime if well used. This corresponds to embodied energy of 0.075MJ per km, rounded up to 0.08MJ for clarity.

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