What Does "Eco" really mean?

Thursday 21st April, 2011
In the world right now, particularly related to motoring, you'll see many "Eco" terms thrown around. Tag-lines such as Eco Friendly, Green, Environmentally Friendly, Zero Emissions etc. But what do they really mean and which are most important? I'll try and offer some background.

Fuel Efficiency

Whether you measure fuel economy in miles per gallon, litres per 100Km or even miles per litre; generally less is more. If you have one car that does 30mpg and another that does 45mpg, it's pretty clear that one is 50% more efficient than the other and uses less of the world's precious resources. Or is it? Well, yes and no.

When comparing fuel economy, you have to ensure you are comparing like with like. Imagine you have 2 children - one eats 2 apples a day and the other eats 3 bananas - which is the most efficient? How do you compare apples with bananas? You can't. Well, the same goes for petrol and diesel. They may both be fossil based fuels but they are not the same and comparing the economy of a petrol car with a diesel one is just plainly inaccurate, at least from an environmental perspective. Sure they may cost about the same, but that's just an economy thing and based upon supply/demand. Once upon a time, diesel used to be significantly cheaper than petrol but then, as demand increased, you'll now see diesel costs significantly more.

Petrol and diesel are both refined from Crude Oil, but in very different proportions. In North Sea Brent Crude we find a proportion of 59 litres of petrol to every 40 litres of diesel, around 50% more, so a 55mpg diesel car is actually using up those precious resources at a faster rate than a 40mpg petrol car.

So, being "green" isn't just about using less fuel, it's using less of the right fuel. Ideally, cars on the road would be fuelled such that our petrol and diesel is used in the same proportions as it is refined. As we already use a lot of diesel for freight in trucks, vans and trains; that leaves a surplus of petrol that needs to be used by passenger cars. It's why petrol has become cheaper since people moved to diesel passenger cars and also why hauliers are finding diesel fuel so much more expensive. There's a certain irony that, as fuel prices rise, more people are switching to more economical diesel cars - resulting in the price of diesel fuel going up further and up to 10 pence a litre more than petrol in some outlets.


With terms like "Global Warming" being thrown around, people turned to CO2 as the enemy. They say that the increase in amounts of CO2 in the air are acting as a "Greenhouse Gases" and raising the temperature of the Earth, melting our polar ice caps. This is all just a theory and none of it has been proved at all. Our Earth is part of a Solar System that is on a steady journey around our Universe that takes hundreds of millions of years, we might just be passing through a warm bit at the moment and things could cool down again later. Nobody truly knows.

In science classes at school, you would likely have studied the Carbon Cycle. Carbon is part of all living things and transfers from one to another in a complete cycle. Essentially, the plants convert CO2 to Oxygen and the animals convert it back again. We can't really create or destroy carbon, just convert it from one form to another and over time, as we've burned wood and oil for fuel, more of that Carbon is currently in CO2 form. Deforestation in places like the Amazon rain forests is an obvious contributor here. Burning 242g of wood (cellulose) in the air actually releases 264g of CO2 so it's easy to see why CO2 levels are increasing. Something as simple as mowing your lawn and then burning the cuttings will actually release more CO2 into the atmosphere than their own weight. When you go as far as heavy carbon fuels, like petrol, they may emit twice as much CO2 as their own weight when combusted. You may notice on the same table, however, that Petrol (Gasoline) actually emits less CO2 than the burning of Coal or Wood.

So the world now has a focus on low CO2 as it was defined, in places like the Kyoto Protocol,  a Greenhouse Gas that was dangerous to the future of our planet. Our cars are now taxed based upon their CO2 emissions but turn a blind eye to other emissions like NOx which are actually also Greenhouse gases. We also ignore emissions like Carbon Monoxide and Carbon particulates which, when oxidised in the atmosphere, also generate additional CO2.

Ultimately, the only way you can create less CO2 is to burn less fuel so the only place we should really tax CO2 is on the fuel. There's little point in applying zero tax to a "low CO2" diesel car that does 200,000 miles a year and applying high tax on a petrol V8 that only comes out twice a year - they only emit as much CO2 as they burn from the fuel that powers them. Tax what goes in, not what comes out.

Local Air Pollution

Cars like hybrids and battery powered Electric Vehicles are said to reduce local air pollution around our towns. Quite simply, the batteries are charged from energy that was generated elsewhere and then the car is driven around town with no tailpipe emissions. Sure, this is correct, but it does just move the problem from one place to another. Would local air quality be improved around a coal-fired power station if its workers all drove EVs? No, the power station would just need to burn more coal to power them, resulting in more emissions in the local environment around the power station.

There is nothing more myopic than measures to address "Local Air Pollution", it just moves the problem from one place to another. Sure, running around London in an electric car may help those dangerous pollution levels around Marylebone Road but it just moves the air pollution issue to Nottinghamshire or Yorkshire where those power stations have to throw a few more lumps of coal on the fire to power them.

Air Pollution is always local to somebody and the only true way to reduce it is to use less carbon fuel.

Air Quality

Technologies like hybrid, catalytic converters, diesel particulate filters and low sulphur fuel have helped improve tail-pipe emissions significantly over the years but, if you've read my article on emissions, you'll realise that manufacturers often only use these tools to suit themselves.

Once upon a time, we used to compare cars based on 0-60mph times. Manufacturers would do anything to improve this stat, often using a long 2nd gear to ensure the car could hit 60mph without having to change gear to 3rd; wasting precious time. Then we focussed on mpg at a constant 56mph - so manufacturers made sure that if a car burned a lot of fuel, it certainly didn't do it when travelling at that magic 56mph speed.

Now we focus on CO2 and they're using every trick in the book to ensure the numbers are low, at least on the official test. They don't really care outside of that and there have been numerous horrific claims for how much CO2 is created by some cars outside of the ranges used in the official test cycle.

But air quality doesn't just mean CO2 and it's other pollutants like NOx, Carbon Monoxide and Particulates that create the real threats to our health. They aren't usually shown on car sales websites but the data can be found without much assistance. My own Green Awards researched and awarded vehicles for being the least polluting overall in their class. If you really care about air quality, don't just look at CO2. You can see emissions figures for cars on sale in the UK in the Green Rankings view on milesperlitre.com.


Maybe you now see that for every argument there is usually a counter argument.

If you drive a Smart fortwo, with the 800cc diesel engine, you could easily claim that you drive the most fuel efficient car on sale in the UK. Indeed, it will go 18.8 miles on just one litre of fuel. With 40 litres of diesel available from a typical barrel of Crude Oil, that means this car can go 752 miles from a whole barrel of Brent Crude.

But what if we compare to the most efficient petrol car in our database, the Toyota Auris Hybrid which will do 16.3 miles on each litre of fuel. But there are actually 59 litres of petrol in each barrel of Brent and so it will actually go 961 miles from a single barrel of Crude - over 200 miles more than the Smart, and it has 5 seats!

You can claim that your car emits less than 100g of CO2 for every kilometre you drive, so "clean" that it makes you exempt from the congestion charge. But if the side effect is a load of horrible CO, NOx and particulate emissions, as seen in the Citroen DS3, it's a bit of a shallow claim and you're arguably much worse for local air pollution than 60% of other vehicles currently on sale in the UK.

You can claim that you drive a "zero emissions" electric car but, ultimately, you're just adding around 24kWh of electricity demand to the National Grid for every 100 miles that you drive - around 13Kg of CO2 based on the average energy mix but actually much higher if you consider that the grid becomes less efficient as we add more demand to it.

The best way to be green is to use the lowest amount of fuel possible. This involves turning off lights and other electrical appliances that aren't needed, walking when possible on short journeys, or taking a job closer to home. If you move house to a location that is half the distance from your office than your current one, you'll immediately halve the carbon emissions from your commute. If you work from home, you'll eliminate it completely. If you share a car with a colleague or neighbour (Carpool) on the same journey, you'll also potentially halve emissions. If you drive slower and/or more economically, you'll reduce pollution levels further.  Try to take the bigger picture into account before looking at headline CO2 or fuel economy figures..

Ultimately, try not to mix up the terms Ecological and Economical; they're two entirely different things and it's not just what you drive but how you drive it that counts most. Simply not going to the office and working from home, or even sharing a car to work, may save more emissions and natural resources than changing your car ever will.

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