Six good things about petrol

I hate petrol [1].

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.

A water molecule is made of up two hydrogens and one oxygen.

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.

[1] Gasoline, for my North American readers.



  1. Ian, great blog and so true in many respects. Here at UBC we have a lot of expertise in hydrogen infrastructure and power generation via fuel cells. Mercedes has just moved their fuel cell manufacturing plant here to take advantage of the pool of hydrogen engineers in fact. However there seems to be three problems that keeps stumping the market: 1. hydrogen is a slippery gas, finding its way out of most metallic storage vessels and pipelines; 2. the platinum catalysts used in PEM fuel cells is massively expensive and needs to be replaced every few years making not only the CAPEX eye-watering, but the OPEX also, leading to poor total cost of ownership; and 3. compression of hydrogen is massively energy intense and hence expensive. There is a H2 bus network in Whistler but due to the cost of H2 production the H2 is actually shipped from either California or Quebec! I wonder what the CO2 footprint of that is… At UBC, as part of our Living Lab program, we have just signed an MOU with the Fraunhofer Institute to begin to overcome some of these issues. It’s great to see Scottish policy, once again taking a step forward (way beyond Whitehall), providing a clear and consistent message for industry.

    1. Good points, Iain. My motto on such things is always, “If it was easy, we’d have done it by now”. 🙂 As long as its a technological challenge (both in terms of operation and cost-effectiveness) then its surmountable, IMHO. I reckon that all new forms of energy use, and especially those aimed at replacing petrol in our transport system, will be always be expensive and tricky to begin with and that’s something we have to face up to as voters, as politicians will rarely look far enough ahead.

  2. Whilst I agree with your sentiments, I believe that we need to remember that it is not petrol that is the problem it is our use, or squandering, of it that is the problem. I have heard that the biggest production of CO2 in a vehicle’s lifetime is when it is built. So even if we could quickly change over to a hydrogen based system we would still be causing climate problems. What we really need to change, in conjuction with engineering solutions, is people’s attitudes and their assumption that we all have some inaliable right to travel when and wherever we want.
    When I went to school, late 60’s & early 70’s we all got there either by public transport, walked or biked. I don’t think the phrase ‘the school run’ existed as far as secondary school children went. At my son’s school, 1998 – 2005ish, large numbers of children were taken to and fro by parents; many (due to being able to choose your school) walked past perfectly good schools in other towns to then catch buses to get to their school. I know of one family of four boys who all went to different schools (they lived within walking distance of a school with a good reputation) – how much fossil fuel did that all cost?
    At a local meeting regarding climate change on trying to fix the next date for a meeting the organiser announced that next month was out as she was going on holiday to Cuba! I expected comments to be made, but the only ones were along the lines of ‘lucky girl’.
    We need to change the way people think and make them realise that resources need to be conserved for future generations.

  3. I like how you mentioned that petrol is quite popular due to its many advantages, such as easy storage and fast release of energy. That’s wonderful to learn since I’ve been thinking about whether to get a car which runs on petroleum or one that runs using biodiesel. I’ll keep your article in mind while assessing which would suit perfectly for us. For the time being, I’m leaning towards petroleum. Thanks!

    1. Except biodiesel has all the same benefits of petrol and can be used in a standard Diesel engine.
      Have you looked at hybrids?

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