I have written on the subject of providing biofuels to replace the current 54 million tonnes of oil (equivalent, since most of the crude is refined by fractional distillation and catalytic cracking) currently used in the U.K. for fuel. I conclude this is impossible, as noted in previous postings, as a status quo, but that by massive reductions in transportation requirements of the order of 90%, the remaining 10% does become potentially achievable in terms of bioethanol got from wheat grass, which is effectively an agricultural waste product, especially if a specifically adapted engine were used, to match ethanol for gasoline nearly weight for weight in terms of power output. However, providing fuel is not the only requirement for imported oil, since an additional 13 million tonnes are used annually for industry. Looking around this room, I am unable to see anything that does not depend at some stage in its creation on oil either as a chemical raw material or/and as a fuel to drive the processes of its manufacture.
In principle, 13 million tonnes of oil "rape seed", say could be extracted from 6.5 million hectares of arable land (at 2 tonnes/hectare), which is 65,000 square kilometers (km*2). And guess what? ... that is exactly the entire area of arable land available in the U.K.! So if we grew nothing else, grew no food at all, we might just about meet demand! There are higher oil-yielding crops e.g. to produce palm-oil, which come in at (ideally!) 8 tonnes per hectare, and so this would require turning over "only" around 16,000 km*2 for the purpose, but still usurping 25% of our food production.
So, it's not only fuel that we need to find a replacement for, to avoid a "siege" caused by a shortage of imported oil. Now this is a very tricky one. True, we could take half the 5 million tonnes of bioethanol that could be produced from wheat grass and crack it into ethylene (ethene), and convert that into hydrocarbons, but assuming a 50% overall yield, that leaves us with just 50% x 5/2 = 1.25 million tonnes of chemical hydrocarbon feedstock (or about 10% of what we presently use) thus signaling the loss of a huge proportion of our industry. We would be left, too, with just being able to fuel about 4.5% of our current transportation by the left-over ethanol, or around half of what is still running having cancelled most plane flights and reducing our fuel economy by living in localised "pod" communities of around 20,000.
Hence, it is not ONLY fuel that we will run short of and need to adapt substantially our lives around, but everything that is manufactured using oil, and that means EVERYTHING. I am less optimistic having written this.
I summarised some of these points in a Letter to the science magazine "Nature", which was not printed through pressure on space (a nice analogy to the human condition!), so I include the text below.
Dear Professor Rhodes,
Thank you for your Correspondence submission. An editorial decision will
be made shortly.
SIR - In his letter "Biochar and biofuels for a brighter future" (Nature 443, 144; 2006) M.H.B.Hayes gives a number of examples of biofuels and platform chemicals being produced from cellulose materials, which translate into an annual production of some hundreds of thousands of tonnes. This is encouraging, but we should not be misled from the colossal quantity of petroleum based fuels and chemical feedstocks that we currently use and need to substitute with their bio-equivalent. In the U.K. we consume 67 million tonnes of oil annually, 54 million tonnes of that for fuel (a quarter of this for aviation), and most of the remainder for industry. To produce sufficient bioethanol as a fuel with an equivalent energy output would require twice the area of arable land in the U.K. to grow enough sugar for fermentation. Hence, if we grew no food at all, we could still only meet 50% of our current fuel consumption. Biodiesel production is worse, and we would need about four times the amount of land there is available to meet the demand. Worst of all is biohydrogen, which can also be produced by fermenting sugar, but would require a sugar crop covering about ten times the total arable area of the U.K. to equal the thermal output from burning 54 million tonnes of oil. Furthermore, the fermentation vessels would occupy a volume of 125 cubic kilometers, which is close to the entire volume of freshwater available in the U.K. The details of these and other calculations on meeting future fuel and energy requirements by renewables, nuclear etc. are available at: http://ergobalance.blogspot.com which your readers might find interesting. I often think that the sheer scale of implementing renewables to make any significant substitution for fossil-based resources is not fully appreciated, and it must be if any sensible conclusions are to be drawn.
Prof. Chris Rhodes.