I hate petrol .
As a fossil fuel its combustion contributes CO2 to the atmosphere, and so contributes to climate change. The particulates it emits on combustion contribute to inner-city pollution. Its extraction around the world is a dirty process, despite some half-hearted efforts to convince us otherwise. And the global appetite for oil-based fuels makes the environment, or indigenous people, only a secondary consideration in the oil business. To cap it all, most oil production is from politically unstable regions of the world so that our foreign policy cannot help but be warped by a need to secure our fuel supply.
Put in that light, our willingness to be completely dependent upon it for transport seems quite unfathomable. Absurd, even.
But petrol is just so very, very convenient. Here are six reasons why petrol is a difficult fuel to replace.
1. Oil is relatively abundant. Compared to other sources of energy that are easy to tap, oil is abundant. Oil extraction is artificially restricted to keep the price up (if there was too much in the market at any one time, the price would go down). As reserves seem harder to find, new technology develops way to access oil we previously thought was not accessible. And even though demand increases this simply drives up prices, making extraction from traditionally more inaccessible places most cost effective. There is an issue to do with the rapid rise in car usage, especially in Asia, but we still manage to find more oil.
2. Petrol is relatively cheap. See (1).
3. Petrol has a fantastically high energy density so that it is a really efficient energy to transport. Great for vehicles because a vehicle needs to carry its own fuel, so the greater energy you can get per kg, the better.
4. Another reason petrol is easy to transport is because it is relatively easy to store. It doesn’t require cooling or pressurisation. It can be stored at room temperature and atmospheric pressure without being unstable. You can transfer that energy from A to B (such as filling a tank) really quickly (unlike electricity).
5. Petrol is also very quick to release its energy. Batteries have trouble shifting their energy quickly, and wood or coal are extremely slow. This makes it great for combustion engines. Flammable gases are one alternative, but they can be difficult to store and transport.
6. There is a great infrastructure built up for the distribution of oil and gas. While the turnaround of new cars is such that you might imagine changing the nature of automobiles (Toyota are showing how that can be done with the Prius) in a period of a few years, it is a much harder problem to change the entire infrastructure.
So is there anything that can compete with petrol? Yes. Hydrogen.
But what about biodiesel, I hear you ask? Biodiesel is potentially one short-term solution as it uses the same infrastructure and requires little modification to existing diesel cars. But the land needed to grow the plants to make the biodiesel will come under increasing pressure as we try to avoid deforestation and maintain global food supplies over the coming decades.
Or, what about electric vehicles? They will continue to be a focus of development (indeed, hydrogen powered vehicles effectively generate electricity to run an electric engine, rather than a combustion engine). But batteries take a long time to recharge – you can’t “fill the tank” in a matter of minutes when you rely on a battery. There is, however, a clear role for hybrid cars to reduce reliance on combustion in the short term.
So what’s so good about hydrogen? Firstly, the exhaust from a hydrogen engine is water vapour. Secondly, hydrogen is abundant – although current hydrogen sources come from fossil fuels, you can make hydrogen gas from water (H2O, see the image above). You need energy to do that, but you can create electricity from renewables (solar, wind, wave) and effectively store the energy by creating hydrogen. This neatly negates all those anti-renewable arguments along the lines of “but we’ll have no electricity when the wind doesn’t blow”. Thirdly, when its pressurised so that it’s a liquid, you can transport it, carry it in your vehicle and “top up” very quickly. It’s not as convenient as petrol, as you have to have it under pressure and it is a highly explosive gas, but modern materials make this more feasible than ever before.
The last thing is infrastructure. To change to a hydrogen based transport network will require a decade of development, but I’m pleased to say that the Scottish government has just announced a £3.3 million commitment to create Europe’s largest hydrogen-powered bus fleet. It will be a slow, and expensive, process to convert all road vehicles to hydrogen, but you have to start somewhere. And I, for one, am very happy that we are making a first step towards a petrol-free society….because I hate petrol.
 Gasoline, for my North American readers.