Doctor Diesel

Emissions Impossible?

web02Hi Doc, if one does decide to stick with a relatively “dirty” diesel, say a Euro 5 rated one, how does that affect the overall emissions picture? I’m a bit puzzled and confused by it all – we all like to have a new car from time to time, but I’m not sure that all the new technology isn’t overtaking me and that I wouldn’t be better off sticking with my 2011 Golf TDI Match and making it last as long as I can. Is the new Golf really that much better than mine, and will I really save that much on fuel if I buy a new, more fuel efficient Golf? Is it such a good thing that Britain is making and selling lots of new cars, and particularly lots of new engines? Does anyone offer any calculations regarding the cost in carbon dioxide terms of making a new car, particularly a hybrid, as opposed to running it? I would find it hard to believe that the now complex hybrids are not really heavy on emissions during manufacture – particularly with regard to things like the batteries. In comparison to that, it would not be difficult to imagine that pure electric cars, with what seem to be relatively simple drive motors, and no transmission to speak of, might be a lot less complex to manufacture. In that case, when are they likely to become cheaper? How much is recycling of metals, aluminium in particular, and other materials like plastics, helping to reduce manufacturing emissions?
Colin Cooper, Bucks

Confused Colin? You and me both! You’ve touched on a lot of subjects and I’m not sure that I’ll be able to answer them all, but here goes. There’s a fairly reliable figure for manufacture of any car of 750kg of carbon dioxide per £1,000 retail cost, making a typical figure of 15,000kg for a middle range hatchback like a Golf. That same Golf produces, in the real world, say around 150g/km of carbon dioxide per kilometre or 2,500kg per 10,000 mile year. So its manufacturing emissions are roughly equivalent to six years of typical usage emissions. How one can relate this to buying habits, and whether it justifies your purchase of a newer and “greener” car that will maybe emit ten per cent less Carbon dioxide in production, and ten per cent less in usage is hugely difficult to assess. But down at the end of the ownership chain your new Golf eventually displaces some really nasty old diesel that is best off the road, and if people stopped buying new cars then the urban air would never get any cleaner.

I feel that there’s a significant issue regarding performance that’s rarely tackled, that of escalating performance. When new models are introduced, there are inevitably performance gains, and often engines are uprated when new models are introduced. Do we really need that inevitable power-to-weight ratio boost? Ever-increasing available performance surely makes a nonsense of existing speed limits, targets for CO2 emissions reduction, and the associated issues of road safety and accidents, does it not?

To move on, the batteries of hybrid cars, and the batteries that power many portable electronics, use significant amounts of the rare element Lanthanum, which is mostly sourced from China, and 20lb (or £500 worth, of a total battery replacement cost of £2,500 plus) of it went into every one of the six million Toyota hybrid batteries manufactured to date. These batteries are actually lasting exceptionally well, but as yet nobody has yet started commercially recycling the lanthanum – or perfected a commercial way of doing it – all 50,000 plus tonnes of it! No wonder the Chinese are happy that they have a near-monopoly in this material. On the bright side, factories manufacturing cars have made some stunning achievements in reducing emissions and in energy usage over recent years. Take aluminium; recycled aluminium requires less than ten per cent of the energy to produce aluminium from its ore, it’s easy to refine and re-use, and the more and more aluminium that gets into circulation for car manufacture, the lower the effective cost. That’s why manufacturers are using more aluminium, as well as for vehicle weight reduction. Weight reduction means less energy to accelerate a car, although it’s worth pointing out that a lighter car saves little or no fuel at any steady cruising speed. So cars that mostly eat up motorway miles don’t benefit that much from reduced weight. It’s also worth pointing out that much of the weight reduction in today’s cars is achieved by using special high strength and ultra high strength steels, where thinner sheeting and welded components can be used that are as strong as thicker but more primitive steels. But some of these special steels themselves require more energy to produce and, in the case of boron steel sheet, they also require heating to 700 to 800 degrees Celsius for “hot stamping” to press them into their final form, rather than cold forming, which obviously uses more energy during production.

Regarding electric car drive motor costs, you just can’t get any meaningful cost figures today, but undoubtedly, once produced in high volume, they should cost a lot less than any internal combustion engine – but how long will true mass production take to arrive? I’ll finish by throwing a somewhat unrelated spanner in the works that merely shows that all which might seem obvious sometimes is not. Here we’re looking at the economics and energy facts relating to rechargeable electric bicycles. Do all the figures and you discover that their drive motors, rated at just 250 Watts continuous output, can deliver running costs of mere fractions of pence per mile. But once you start to amortise the capital cost of, say, a £1,500 bicycle over five years at 1,500 miles a year, the picture is considerably less encouraging, because depreciation is then twenty pence a mile. What is fascinating is the fact that these electric ‘bikes are actually very green in running costs, and actually they are greener than pedalling yourself, with no assistance. How come? Because fossil fuel conversion at the power station into electricity is more efficient than conversion of food into human energy for pedalling, so heavy on energy are the systems that produce much of our food. So, apart from the exercise, the fine activity of cycling isn’t actually as good for planet Earth as using an electric bicycle. Enough of my ramblings Colin. I hope that at least I’ve given you food for thought, even if you are probably still puzzled and confused. But I would hang onto that Golf Match for a couple more years, if I were you – it was a really classy model. Regards,

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