Most of our readers might not be familiar with LPG (liquefied petroleum gas) but it's a fuel that is very hot in countries like Belgium, Germany, Italy, France and Australia. LPG is a mixture of hydrocarbon gases (propane and/or butane) that is liquefied and then used as a fuel. It is non-toxic and non-corrosive, and it burns cleaner than gasoline or diesel and is much more free of particulates when compared to the latter. However, it's got a lower energy density, with a lower mpg. Still, since many governments impose lower taxes on LPG than other fuels, using LPG is still usually quite cost effective.

I found an article on the French site Moteur Nature that states that low taxes on LPG is actually counterproductive. The reason? The cost of CO₂ per km becomes cheaper, and therefore more pollution hits the air. Since virtually all gasoline cars can be converted to run on LPG, Moteur Nature says this is an open door for people to keep those large SUVs instead of downsizing (I know of a couple such cases among my acquaintances). Here is a good example:

Citroën C2 1.1, a subcompact with a small gasoline engine, pollutes 141 g of CO₂ per km. It burns 5.8 l/km (40.5 mpg). At France's price of gasoline, 1.35 EUR/liter (that's like 7.8 USD/gallon), we have to spend 78.29 EUR to run 1000 km and we'll produce 141 kg of CO₂.

Then, take a more polluting car: Ford C-Max 2.0, a compact people mover. It pollutes 169 g of CO₂ per km. It burns 10.5 l/km (22 mpg). At France's price of LPG, 0.75 EUR/liter (that's like 4.4 USD/gallon), we'll spend 78.29 EUR to run 1000 km while producing 169 kg of CO₂.

The conclusion is that LPG is not a good solution if we want to reduce CO₂ emissions. Calculating for the complete lifespan of a car (about 150,000 km / 90,000 miles), a car running on LPG will produce 4.2 tons of CO₂. Meanwhile, Germany just reduced government support for biofuels but has kept tax breaks for LPG. Moteur Nature is against that policy.

[Source: Moteur Nature]