U.S. may need to Import Corn.

Such is the expanding nature of the corn ethanol industry in the U.S., that the nation could switch from being the world's biggest exporter to corn to a net importer. In the meantime, however, U.S. farmers look set to make a killing on the world markets where corn has reached its highest price for a decade. If the U.S. did stop exporting corn, it would have a drastic impact on the global corn industry... and on world food supplies. This is a good example of how, in the global economy, no commodity can be considered in isolation. Why is there so much interest in corn-ethanol now, in a country which formerly could claim to be the world's greatest exporter of oil? The short answer is "foreign oil-imports". The U.S. is now absolutely dependent on imported oil, having passed its own national "Peak Oil" in the early 1970's. Conflict in the Middle East, and threats of further actions from either side mean that supplies of oil might become increasingly insecure. Additional pressure on what is often overlooked as a finite resource must increase from burgeoning demand from the Far East, and the West must come head-to-head in the near future with developing countries like China and India for this same resource. Indeed, it was announced this morning that the Anglo-Dutch company Corus (formerly British Steel) is accepting a £4.3 billion ($8.1 billion) takeover offer from its Indian rival Tata Steel. Hence, there is a growing desire to develop "home-based" energy sources, and corn-ethanol is popular in the U.S. as a potential "secure" fuel for the future, even though the Energy Returned on Energy Invested (EROEI) remains the subject of considerable controversy. As I have pointed out before in these articles, ultimately growing fuel must come into direct conflict with growing food, and having reached the half-way point of "world "Peak Oil", we could see "Peak Food" if conventional agriculture were to become compromised by the commandeering of corn crops for ethanol production. Not that the two matters are disconnected, since most of the corn is grown using oil-fuelled farming methods including the chemical fertilisers used to force-up yields of corn and all other crops in the first place. It is all very complicated and I question whether in reality corn-ethanol will solve the problem of fuel supply, ultimately.
Most analysts do not see an immediate dramatic switch from exporter to importer, but among his other "green" proposals, President Bush has called for the U.S. to be using 35 billion gallons of renewable fuels by 2017, and it is hard to see how such a massive target will be borne by the industry, without curtailing its exports. This amounts to a five-fold increase in ethanol use, and indeed even Bush admits that the constraint on the final production level is how much corn the American farmers can actually grow. Current law requires that 7.5 billion gallons of renewable fuels (mostly ethanol) be used by 2012 (the end of the Mayan Calender?), which is somewhat above the 2006 production figure of around 5 billion gallons.
Producing 35 billion gallons of ethanol from corn alone would absorb the entire present U.S. corn crop at current production yields - about 11 billion bushels - which would appear to put the kibosh on the whole scheme. If ethanol is burned in suitably adapted engines, a par weight for weight (roughly) with its equivalent of oil-based fuel can be drawn. Hence, 35 billion gallons is equal to around one billion barrels of oil. Now the U.S. gets through about one quarter of the world's produced oil (30 billion barrels), or 7.5 billion barrels annually. So, even if it did use its entire crop of corn to fuel cars, trucks and planes rather than people, it could still only meet around 13% of demand. I concede that this figure could be increased by suitable hybrid engines, based on fuel cells but these have yet to be developed, and the real existing oil reserve is already running down by the second. Thus current demand cannot be met according to any sensible analysis of the facts. Even using also not fully developed technology which employs enzymes to break down the (woody) cullulosic material in plants e.g. from switch grass and corn husks into ethanol, and diverting a realistically possible proportion 20% of the corn crop, the U.S. might meet a total 5% of its current fuel demand from corn. The loss of 20% of America's corn crop would definitely hit the capacity of the world market and probably countries such as Argentina and Brazil would meet some of that resulting shortfall.
The conclusions are clear enough, however, that along with all other Western countries, transportation must be cut in the U.S. to meet the needs of a more locally based economy, which reduces total fuel demand probably by around 90%. In this way, a mix of electricity (supplied from all sources including nuclear from thorium) could sustain tram-systems for moderately-sized urban conurbations and electrically-based (fully or hybrid) vehicles for essential use. An increased exploitation of coal could also place more fuels on the shores of the U.S. (and within all countries) made by liquefaction processes, but that would need to be done paying due regard to its environmental impact. Nor is it realistic that China and India can attain a Western standard of living that even the West can no longer bear. Every one of these analyses points away from globalisation and its associated extensive transportation, especially in moving goods around the world. Local production avoids this entirely. Localisation must happen either through default or design, and default is the hard option I would prefer to avoid.

Peak Oil within 12 Months... but that's good, isn't it?!

A conference held in Cardiff with the title "One Planet Agriculture" is underpinned by the theme that global supplies of oil will begin to ebb within 12 months. I have sensed murmurs about "fuel rationing", and optimistic reassurances that when this happened during and post WWII it did not cause the collapse of society. However, that was an entirely different society from the one that is now hosted on these shores. Hopefully there remains sufficient integratedness and national identity to hold it together now. Indeed, some hardship may forge cooperation within the necessarily localised communities that will pocket themselves when casual free-range transportation is no longer an option. Transportation itself must be the first mechanism to be hit by a restricted availability of fuel. This however, does not only mean that we can probably forget about jetting-off on cheap foreign holidays, and commuting from say Cardiff to London to get to work, but also the carriage of all goods including food, within that mighty mechanism of Globalisation. We will need to produce locally, and perhaps as happened in Cuba when more recently than WWII the Russians cut-off the liberal supplies of fuel and fertilisers that were their reward for being that sensitive outpost of Communism, a new society will flourish in small regional pockets, supplied by local farms. It is a point worth stressing too, that the black-gold on which the modern world has become enplaced is not only used to be refined into fuel, but it is also a necessary chemical feedstock for industry, and everything now depends on imported oil either as a fuel or a raw-material for manufacture, or both of these things. I would not be typing these words, were it not for the petroleum-based plastics industry that has somewhere churned-out this, yet another of the millions of keyboards upon which billions of hands mark out their daily diary of a lifestyle that has become customary in that part of the world. Whatever happens, we must maintain the internet and the world communications network, rather than humanity disappearing into packets of isolated darkness hidden from one another's view. But nonetheless, humans themselves will largely stay put and act on a largely locally focused level.
The Cardiff conference was organised by the Soil Association, who think that while the agriculture of the 20th century was driven by government-run, centralised systems of farming and food distribution, in the 21st century (and probably for ever more) its basis will be localisation. So that means we are now in the last days of Globalisation. No one can say precisely when Peal Oil will hit, but all serious estimates are than it will happen sometime before 2010 - i.e. within about 3 years, and so that "within 12 months" projection doesn't look so wild. The world will not find itself without oil overnight, but its costs will soar as the sweeping tail of oil reserves is steadily extracted. It is estimated that by 2021, we will have just half of the current oil reserves left; however, that oil is as I have explained before, more difficult to extract and to refine - it is a heavier, dirtier oil that needs more intensive processing. But long before then we will have been forced to change how we live.
Patrick Holden, director of the Soil Association put it thus: "in hindsight, the fossil fuel era will be described as a sort of extravaganza where we lived beyond our means, treating capital as income and squandered all this energy." Well said, and indeed the rapid growth (mathematically close to exponential) in the world population can be plotted on the same function as used to describe oil extraction. The global family has worn and eaten oil, since it is used to run modern agriculture, along with producing the forcing artificial chemical fertilisers that have resulted in the depletion of soil in most of the world, such that much of its organic (humic) component is gone and it is ever closer to being a mere lifeless solid support. Farming will have to become "organic" because there will be no choice. It is often portrayed that we are "bad people" for our profligacy, and lack of foresight that resources are finite and mutable. However, we are just the same as any species, even bacteria. When bacteria are placed in an environment of plenty, e.g. on a Petri Dish, to grow, their rate of growth follows an "S-shaped curve". There is an initial slow rise, until a critical population of bacteria exists, and then a very rapid population explosion, until finally the food runs out, the population levels off and then they start eating each other. It is not a nice comparison when placed into human terms, and yet we are beginning to see wars over that particular precious resource of oil. So, maybe we are not so different from bacteria, but we should be. Greed only came about on a mass scale when there was sufficient plenty for acquisitiveness to reach planetary proportions - and that, our present consumer society, is entirely based on oil.
We are poised on the fulcrum of Peak Oil - the balance point between plenty and dearth. Only by adopting a programmed transition to lower energy "localisation" can life become sustainable. It may even become more worthwhile, restoring the sense of connectedness that seems to have been lost in the soulless material void of "more". That is not wealth at all. Spiritual and human values might begin their own rise in a new phase of consciousness. However, the practicalities are that it will take perhaps 10 years to augment a fully alternative structure of localisation, and so we must begin today, while there is still sufficient oil left to make it happen. In five years it may be too late.

No Sense to a Hydrogen Economy.

This is the conclusion of Ulf Bossel in a recent paper published in the Proceedings of the IEEE (2006, Vol. 94, page 1826). Bossel is with the European Cell Forum, based in Switzerland, and has spoken out previously and convincingly on the topic of "hydrogen", pointing out the energy and economic deficiencies of the putative "hydrogen economy". As he stresses, the establishment of a sustainable energy future is one of the most pressing tasks for mankind. As fossil fuel resources begin to run-out, he predicts that the energy economy will change from a chemical to an electrical base. However, to make this transition is not simply an act of political will, but the underlying science to do so must be sound, and be based on proven technology and existing engineering experience - not pie in the sky proposals! The process (the ride down the rough side of the failing oil production Peak) will take many years and of course it must start as soon as possible, while we still have existing resources in reasonable plenty to utilise in the fabrication of new technology. A secure sustainable energy future cannot be based on hype and activism, but has to be built on solid established foundations of known science and engineering. Bossel (as usual) makes a quantitative analysis of what is involved and concludes that only 20%-25% of the source energy needed to synthesized hydrogen from natural compounds (e.g. methane from natural gas) can be ultimately recovered by efficient fuel cells. This is not good. In my posting on Monday "Hydrogen for Oil?", I settled for a figure of around 35%, which appears rather optimistic in the light of Bossel's analysis. It might appear then, that anywhere up to a doubling of the number of wind turbines and nuclear power stations that I reckoned (32,000 2 MW turbines or 21 Sizewell B type 1.2 GW nuclear power plants) would be needed to make enough hydrogen to supplant the amount of fuel currently used to run the nation's road transport fleet. As an energy carrier, hydrogen cannot compete with electricity (electrons). To quote Bossel: "As the fundamental laws of physics cannot be chanced by research, politics or investments, a hydrogen economy will never make sense."

Along with all the problems of storing hydrogen, which needs high pressures and cryogenic cooling, even if it is adsorbed in porous materials like zeolites (none of which have met the storage capacity criteria demanded for them; last posting here "Hydrogen Storage in Zeolites"), and the fact that it makes some metals brittle over time and hence leaky (NOT good for an explosive gas), it might be better to store the electrons in "batteries" to get a better overall efficiency of 50% than 20-25% for hydrogen, when we could get away with around 20,000 2 MW or 8,000 5 MW turbines. That same job could be done using another 13 nuclear power plants, to be built on top of the 30 or so that will already be needed by 2025, to replace the current generation of them.

If we were to localise our society and cut transport by 90% we would be down to just 10% of this, needing only 2000 2 MW or 800 5 MW turbines. There would be no planes though, and if we want to keep them flying some other means must be found to do so.

Using energy in the form of electrons means that the existing electricity distribution infrastructure could be adapted, rather than introducing a wholesale entirely new hydrogen storage and distribution network on a gargantuan scale.

Neither biofuels nor biohydrogen can meet the huge present demand for transportation fuels either, and would vastly exceed all available arable land for food production even to provide 10% of what is currently used to run cars and road transport in general. However, along with electricity, biofuels could satisfy much of the energy needs of localised economies.

Hydrogen Storage in Zeolites.

The following section is taken from an article I am writing for Annual Reports C: Physical Chemistry, and published by the Royal Society of Chemistry. I can give the actual references if anyone wants them. My conclusion is the future doesn't look good for the putative Hydrogen Economy", given the difficulties encountered in storing the gas. I don't see any realistic use of H2 on the large scale, as I explain.

In an effort to address the twin-problems of dependence of nations upon imported hydrocarbon fuel and forcing climate change through global warming induced by emissions of CO₂ from burning fossil fuels, hydrogen is being investigated as a clean, carbon-free fuel that could be made on a national (or regional) basis.⁴ However, hydrogen is not actually a "fuel" but an energy transfer (storage) medium. That is to say that hydrogen is not available in an aboriginal form as are oil, coal or gas, (which are known as "primary fuels"), but rather it must be "made" by some artificial means. Most of the hydrogen currently used in the world (mainly for chemical purposes, such as the wholesale manufacture of ammonia for fertilisers) is produced from natural gas by a process known as "steam reforming" sometimes with the use of a zeolite as a catalyst or to separate²⁴ the carbon monoxide formed when the carbon is "extracted" from methane by its reaction with steam: CH₄ + H₂O → CO + 3H₂, or to separate carbon dioxide when that CO is used to squeeze-out another molecule of H₂ by adaptations of the "water-gas shift reaction": CO + H₂O → CO₂ + H₂. Zeolites are also used more generally to remove CO₂ from natural gas.²⁴ Ideally, hydrogen should be "green", i.e. made by electrolysis of water using electricity produced from renewable sources, e.g. wind power, but it is arguable that those electrons would be more effectively used in forms of battery technology for driving vehicles and other electrical appliances. Nonetheless, efforts toward the putative hydrogen economy continue, and of greatest concern is the development of materials in which hydrogen might be effectively stored, including zeolites.⁴ A major advance has been made, which it is proposed may help address the vexed problem of storing hydrogen on the enormous scale which will be required if it is to be used to power vehicles to any significant extent. Researchers in Spain²⁵ have found that a zeolite-Y partially exchanged with magnesium cations (Mg²⁺) has an unprecedented high adsorption enthalpy of -17.5 kJ/mol, which is close to the value of -15 kJ/mol recently proposed as optimum²⁶ for a material that will efficiently both bind and release H₂ according to the demand of its supply: i.e. the gas should neither be too strongly adsorbed otherwise it will not be released in a "fuelling station" situation, nor too weakly adsorbed otherwise the material is ineffective for storing it in the first place. The effect is attributed to the high polarising power (e/r) of Mg²⁺ cations. The effect of polarisation (see discussion in previous section) both induces an I.R. active vibration from adsorbed H₂ and reduces the fundamental H-H stretching frequency from 4163 cm^-1 measured by Raman spectroscopy in the gas phase for unperturbed molecules, in this case to 4056 cm^-1. The value of -17.5 kJ/mol is significantly greater than those previously reported for the adsorption of H₂ in alkali-metal cation exchanged zeolites,^22,23,27 and is around 20x higher than the liquefaction enthalpy of H₂ of -0.9 kJ/mol (at 20.45 K). Nonetheless, there does remain the issue of exactly how much hydrogen can be imbibed by a zeolite for practical purposes. For commercial applications, an acceptable energy density for a hydrogen storage tank is deemed to be that it can efficiently hold an amount of hydrogen equal to 6.5 wt.% of the weight of the tank and 62 kg H₂/m³ in terms of volume.^27,28 However, although investigations of hydrogen storage methods have been carried out for over 30 years, there has been no single method devolved which fulfils these demanding criteria. Some approaches meet the weight target, but occupy unsatisfactorily large volumes (e.g. tanks of compressed hydrogen gas) yet others achieve the volume target but not the weight ratio (e.g. metal hydride absorbents). To approach the matter from a theoretical perspective, a molecular mechanics study has been made of the thermodynamic limits on hydrogen storage in sodalite framework materials, built up from TO₄ (where T = Al, Si, Ge, P) terahedra.³⁰ It is concluded that cation-free sodalite structures could accommodate eight hydrogen molecules per cage as an optimum loading, at which point the density of the hydrogen is almost equal to that in liquid hydrogen, and the calculated densities of 65 kg H₂/m³ can theoretically at least be achieved for most structures based on sodalite. For pure liquid hydrogen the figure is 70.8 kg H₂/m³ which is the normal density of the liquid at a temperature of 20.28 K. However, to liquefy hydrogen costs around 30% of the energy that might be recovered from the material as a fuel.³¹ There is however a considerable discrepancy between the loading of sodalite found experimentally³², 0.26 and 0.4 wt.% for all-Si ( Si₉₆O₁₉₂) and AlP (Al₄₈P₄₈O₁₉₂), and the calculated³⁰ capacities of 4.8 and 5.2 wt.% respectively. However, the theoretical maximum capacities are based solely on energetic considerations, and do not address effects such as ions, water or other impurities that might act to block access to part of the internal volume of the sodalite crystals. There is also no influence of entropy included in the calculations which are in effect performed at zero Kelvin. In an extension of the theoretical work, adsorption isotherms of H₂ in various sodalite materials were calculated using a grand canonical Monte Carlo method.³³ It is concluded that at loading capacities of technical interest, 573 K and 100 bar, a storage capacity of around 0.1 wt.% might be achieved for each type of sodalite structure. However, the really technologically desirable capacities of above 4% are likely to only be met under conditions of extremely low temperature and/or extremely high pressure.³³ The results make an interesting comparison with theoretically estimated maximal storage capacities for hydrogen in zeolitic materials. In effect, the adsorption can be thought of as a facilitated liquefaction, where the solid-gas interaction causes condensation at conditions of temperature and pressure that are more convenient than those required to form the bulk liquid. One such study³⁴ was made which used the force-field method and performed its calculations within the Discover module of the Materials Studio 2.2 package of Accelerys Inc.³⁵ The progressive filling with H₂ of twelve purely siliceous models of common zeolite frameworks was simulated in order to determine the effect of framework properties including flexibility on the maximum adsorption capacity for hydrogen. It was deduced that the flexible non-pentasil zeolites (RHO, FAU, KFI, LTA and CHA)⁵ show the highest maximal capacities, in the range 2.65-2.86 wt.% of H₂. The predicted adsorption capacities were found to correlate well with experimental results obtained at low temperatures (77K), but these materials are well below the 6.5 wt.% target value set for hydrogen storage in a practical device. The zeolite chabazite (CHA) has received particular attention in its context as a potential material for storing H₂ since it was rated as having the largest capacity of any zeolite in this regard.^31,36 For a H-exchanged (protonic) chabazite, H-SSZ-13 (Si/Al = 11.8), an absorption capacity of 1.28 wt.% was determined at 77K, slightly above that for zeolite-A at 1.24 wt.% and for H-CHA itself (Si/Al ratio = 2.1) at 1.10 wt.%.³¹ The hydrogen is described as "liquid hydrogen" in the zeolite, and it is shown that the available volume of a chabazite (H-SSZ-13) cage can contain seven hydrogen molecules at the density of liquid hydrogen. Actually in the zeolite, the results indicate that at 77K, 57 K above the boiling point of liquid hydrogen, about five hydrogen molecules are confined to each cage. This implies that conditions close to liquefaction are achieved when hydrogen is adsorbed into H-SSZ-13 zeolite at 77K, a result of sufficient importance that the paper was published in JACS.³¹ The point was investigated further by similarly measuring the volumetric uptake of H₂ at 77K and a transmission I.R. measurement of H₂ absorption at 15 K, in H-SSZ-13, (the isostructural silico-aluminophosphate material with the same Bronsted site density) H-SAPO-34, and H-CHA itself. It was found there is an improvement in H₂ uptake when the acid strength of the Bronsted sites is increased (moving from H-SAPO-34 to H-SSZ-13), while conversely, increasing the density of Bronsted sites (moving from H-SSZ-13 to H-CHA) impacts negatively on the adsorption process. The latter result is quite counter-intuitive but an explanation is offered that the additional Bronsted sites are in mutual interaction via H-bonds inside the small cages of the chabazite framework and for most of them the energetic cost of displacing the adjacent OH ligand is higher than the adsorption enthalpy gained in forming the OH---H₂ complex.³⁶ The record set by H-SSZ-13 for a hydrogen storage capacity in a zeolite of 1.28 wt.%³⁶ at 77K and one atmosphere pressure of H₂ gas has been broken using low silica type-X zeolites (LSX, Si/Al = 1) fully exchanged with alkali-metal cations (Li⁺, Na⁺, K⁺).³⁷ Hydrogen adsorption isotherms were determined separately at 77K and a pressure of <>2 and the cations follow the order Li⁺ > Na⁺ > K⁺, in order of the increasing cation radii: 0.068, 0.097, 0.133 nm, respectively. Li-LSX had an adsorption capacity of 1.5 wt.% at 77K and 1 atmosphere pressure, and a capacity of 0.6 wt.% at 298K and 10 MPa pressure, which places it among the highest of known sorbents. The possibility of enhancing the uptake of H₂ by bridged hydrogen spillover was also investigated, for which a simple and effective method was found to construct carbon bridges between the dissociation catalyst and the zeolite to facilitate spillover of hydrogen atoms. By this means, the hydrogen storage capacity was enlarged to 1.6 wt.% (i.e. by a factor of 2.6) at 298K and 10 MPa pressure of hydrogen gas. This is by far the greatest hydrogen storage capacity achieved using a zeolite material at ambient temperature.³⁷ A theoretical study was made of the hydrogen adsorption isotherms for a range of clathrasil frameworks. A clathrasil is a framework with Si₆O₆ as its largest ring aperture. The properties were calculated for twelve known clathrasils and seven hypothetical energetically stable versions. Under all conditions of temperature and pressure, high adsorption energies were predicted for small volume cages (<400a³) in consequence of the larger contact area between the cage wall and H₂. Nonetheless, the H₂ loading into the material is quite low because of the large internal surface-to-volume ratio which leaves little void space for the H₂ molecules to occupy. It is concluded that clathrasils are unlikely to become of any use in practical hydrogen storage applications.³⁸ An experimental study has been reported of the physisorption of H₂ into zeolite types A, X and ZSM-5 under moderately high pressures of 2-5 MPa. The highest storage capacity found was 2.55 wt.% for Na-Y zeolite at 77K and 4 MPa pressure. In CaA, NaX and ZSM-5 zeolites, the hydrogen uptake was found to be proportional to the specific surface area of the adsorbent, and which were associated with the available void volumes of the zeolites.³⁹

In conclusion, the prospect of using zeolites for practical hydrogen storage appears limited. More promising appear to be certain zeolite-templated porous carbons, and for one example a hydrogen uptake of 4.5 wt.% and 45 g/L weight and volumetric densities, respectively, were reported at 77K and 20 atmospheres (2 MPa) pressure.⁴⁰ Still greater capacities for H₂ are reported for porous coordination-framework materials giving uptakes of up to 6 wt.%, at 78K and pressures less than 20 atm., which are therefore likely to receive further attention as potential candidates for practical hydrogen storage systems.⁴¹ I conclude this section by noting one paper⁴² entitled "Hydrogen Storage: The major technological barrier to the development of hydrogen fuel cell cars", which provides a useful survey of the whole contentious business. I would also recommend the wikipedia entry on hydrogen storage.⁴³ However hydrogen might be used, either as a pure substance or as adsorbed into zeolites or other porous materials, the energy costs of cryogenic cooling and compression must be born and factored into the energy balance equation for the hydrogen economy All such efforts to find a substitute for hydrocarbon fuels have brought home exactly how ideal the latter are as fuels, both in terms of energy density and their handling properties, and finding a substitute for them will be a hard act if it can be done at all.⁴

Hydrogen for Oil?

I posted an article "A Hydrogen Economy - Is it Economic?" in January 2006, and concluded that we would need 180,000 2 MW wind turbines or 61 new Sizewell B capacity nuclear reactors to produce sufficient hydrogen to replace all the oil-based fuel used annually in the U.K. What I did not do was to factor in inefficiencies in the use of oil, and so I now revisit the concept bearing this in mind, and arrive at far more encouraging (though still daunting) numbers than these. It is a popular misconception that hydrogen is a fuel. It is not. It is an energy carrier. This means that hydrogen cannot simply be pulled out of the ground like gas, oil or coal, but it must be manufactured in some way. Most of the hydrogen produced in the world (used mainly for making chemical fertilisers for agriculture) is made by "steam reforming" natural gas, which is principally methane, according to the equation:

CH4 + H2O --> CO + 3H2. An "extra" portion of hydrogen can be squeezed-out of the system, by an adaptation of the water gas shift reaction: CO + H2O --> CO2 + H2, and so the overall process may be represented as:

CH4 + 2 H2O --> CO2 + 4H2.

The production of CO2 is naturally undesirable since it is a greenhouse gas, and so ideally a "green" source of hydrogen is wanted, e.g. electrolysing water using electricity generated using a renewable source like wind-power. Now, my question is, how feasible is this in terms of the generating capacity required to produce enough electricity to meet the scale necessary? Currently, we burn the equivalent of 57 million tonnes of oil each year to run the U.K. national fleet of vehicles, including planes (which consume around a quarter of that total, or 13 million tonnes). This leaves 44 million tonnes for road transport.
Fuel used in conventional internal combustion engines is burned very inefficiently, such that around just 16% of its total energy is recovered in tank-to wheel miles. Gas-Hybrid vehicles are far more efficient, and e.g. the Prius is reckoned at 37% tank to wheel. hence we could cut that total oil-bill down to (16%/37%) x 44 = 19 million tonnes of oil. Aviation is a separate issue, and the present calculation refers to road vehicles, because hydrogen-powered planes are very much a concept for the future, if ever).
Even if H2 could be provided on a large scale it can't be used with 100% efficiency either, and I shall assume an efficiency of 70% for the water electrolysis step, and 50% efficiency for an on-board fuel-cell, so that is the tank to wheel efficiency. This gives 70% x 50% = 35 % overall, in converting the electrons to road miles via hydrogen as the energy carrier. It is arguable that this is very inefficient to convert one form of energy carrier to another (electrons to hydrogen) and it is, but it is thought easier to store hydrogen than electrons, until better "battery technology" is developed. However that 35% is close enough to the 37% efficiency estimated for a gas-hybrid "Prius" vehicle that I shall compare oil with H2 on a one for one basis, using the 19 million tonne oil figure that would be required rather than the 44 million tonnes that we currently pour into our gas-guzzling internal combustion engines.

1 tonne of oil = 42 GJ of energy, and 1 kWh = 3.6 MJ. Therefore, 1 tonne of oil = 42 GJ/3.6 MJ = 11,667 kWh.
So, 19 million tonnes of oil = 19 x 10*6 x 11,667 = 2.22 x 10*11 kWh.
Now that's per year = 8760 hours, and hence the generating capacity = 2.22 x 10*11/8760 = 25,342 MW.

Let's look at two ways to generate this electricity: (1) nuclear and (2) wind power.

(1) Sizewell B has an electricity generating capacity of 1188 MW (the thermal capacity is nearer 3,600 MW, and so that inefficiency of converting heat to electrons has already been factored in). Hence we need 25,342 MW/1188 MW = 21 new reactors of this capacity to make the hydrogen to run our road fleet... and this is on top of the 30 or so new nuclear reactors that are needed by 2025 to replace the current nuclear generation which should be decommissioned... or mothballed by then.

(2) Wind turbines will need to be located offshore, in order to use the larger 2MW version with their 80 m long blade which is unpopular on land, for reasons of noise and spoiling the view. More practically, a greater capacity factor is obtained in offshore locations of around 0.4 as opposed to 0.2 for land based sites. i.e. each "2 MW" turbine would give an average of 0.4 x 2 = 0.8 MW. Hence we would need 25,342/0.8 = 31,678 of them, which is down considerably from my original estimate of 180,000, but is still a hell of a lot.
Now, the question remains of where would they go, precisely? I am making a very rough estimate, that the U.K. mainland can be approximated by an oblong 600 miles in length and 200 miles in breadth, giving a coastline of 600 + 200 + 600 + 200 = 1600 miles = 2560 km.
If we put them 0.5 km apart (which is the recommended separation) we could fit 2 x 2560 = 5120 in a single band. So, we need the actual band to be 31,678/5120 = 6(.19) turbines deep, and if they are 0.5 km apart, the band is around 3 km thick.

If the turbines were of 5 MW capacity not 2 MW (there are prototypes of this size) we'd need just 31,678/(5 MW/2 MW) = 12,671 of them /5120 = 2.5 deep, on average, and so the "band" would then need to be of 2-3 turbines on average and would present a thickness of about 1 km or so.

Along with all the problems of storing hydrogen, which needs high pressures and cryogenic cooling, even if it is adsorbed in porous materials like zeolites, and the fact that it make metal brittle and hence leaky (NOT good for an explosive gas), it might be better to store the electrons in "batteries" to get a better overall efficiency of 50% (70% of 70%) than 35% (70% of 50%) for hydrogen, when we could get away with around 20,000 2 MW or 8,000 5 MW turbines.

If we were to localise our society and cut transport by 90% we would be down to just 10% of this, needing only 2000 2 MW or 800 5 MW turbines. There would be no planes though, and if we want to keep them flying some other means must be found to do so.