The Independent yesterday carried a front page banner that there are 33 million cars on the U.K. roads, which includes a rise of 7 million of them in ten years. This is indeed a staggering statistic since this fleet of road traffic presently gets through fuel to the equivalent of around 44 million tonnes of oil each year. The article also points out that 20% of our CO2 emissions are from traffic. That must be just from cars, since around 30% of the nation's entire energy budget is accounted for by the end-use of fuel (planes included), much of the rest of that "energy" coming from gas and coal. Conventional car-engines use fuel very inefficiently, deriving only around 14% of the fuel's intrinsic energy worth in terms of road miles. Burning gas or coal in power stations is done at around 35% efficiency, which is still woefully low, but better than is manged by cars etc. More efficient cars have been devised, e.g. the generation of "hybrids" which produce electricity from revolutions on the road, and use that to power the vehicle at low speeds "in town", a combination which gets 42% of the fuel energy back in the form of tank-to-wheel efficiency. Hence the transport-induced CO2 emissions could be cut by means of vehicles based on this kind of technology. Likewise, combined-cycle coal fired power stations can run at much greater efficiencies than conventional plants, and can additionally produce synthetic oil too.
Now, this gets me onto the salient point of this issue. We seem to be bombarded with information about growth in the developing world (e.g. China and India), how many cars there will be by the year 2050 and so on, based on projected estimates of a linear escalation of trends and numbers. However, to use my analogy about the growth of bacteria, the steeply rising portion of the S-shaped curve that describes this process mathematically only continues to rise while there is sufficient fuel (food) to support such proliferation. In the human case, the fuel is oil (used to run transport and to grow food). We are on the one hand presented with all kinds of projections "to 2050" (i.e. about 43 years hence) and yet there are only sufficient oil reserves claimed with confidence (i.e. about one trillion, or one thousand billion, barrels left) to last for about another 30 years, and that is if we could extract the whole lot, when it is not certain than we can. Oil wells cannot simply be drained to bottom, as extracting oil becomes increasingly difficult, energy intensive and expensive as the well reserve falls. The quality of the oil that is pumped-up falls too, and the material becomes steadily heavier and contaminated with sulphur and other compounds that it needs to be cleaned from before it can be refined into a useful fuel. It is generally agreed that we are close to the point of maximum oil production (production has fallen in Norway now, I notice, pulling that country down into fifth place among the giants of oil exporting nations) and so supply of conventional crude oil will fall inexorably from here on in.
Some of that inevitable shortfall can be offset by building coal-fired combined cycle power plants (which make both electricity and oil), and yet none have been installed as yet, certainly not in the U.K. There are various predictions made about biofuels, which my calculations here show to be unsatisfactory as a means of replacing the current massive volumes of fuel that we rely on, and at best we might produce about 10% and probably a lot less than that, unless we are willing to stop growing food. Of course that would be madness, as in an oil poor world all nations will need to be largely food-sufficient within their own borders. The hydrogen economy looks set to be a damp squib, since the scale of infrastructure and problems in storing and distributing the gas mainly render it unsuitable as a serious contender for an energy carrier (which it is - not a fuel per se).
Hence, 33 million cars on the road in the U.K. is the least of our worries. Than number will fall unequivocally as the means to fuel them runs out. Even if we can extract one third of the remaining one trillion barrel oil reserve at near present output, that is just 10 years worth, with demand breathing harder all the time, and hence the level of car use will fall dramatically within a decade. There may be more fuel made available from "unconventional" sources, but it will become increasingly costly. It must do. Logically too, society will accordingly begin to localise, and it is this eventuality we should be focussing our efforts and plans to meeting. The massive world population of cars is just a flash in the pan; we must try to ensure that the human population will not fail too... and die-off like bacteria!