There is a widely held misperception that the "hydrogen fuel-cell economy" will reduce our need for fossil fuels to run our automobiles: all you have to do is buy a fuel-cell car and, Presto!, no more carbon dioxide. It is just not so. Let me try to explain.

In a hydrogen fuel cell, hydrogen gas combines with atmospheric oxygen to produce electrical energy and water vapor. The electrical energy powers the car and the water vapor is vented into the atmosphere. So a fuel-cell car is clean on the street - no CO2, no CO, no NOx - it emits only water vapor.

But hydrogen is not a source of energy, it is merely a vehicle for storing and transporting energy. In the same sense, electricity is a vehicle for transporting energy.

The hydrogen needed to power a fuel-cell car does not exist in nature; it is not a source of energy to be mined (like coal) or to be pumped out of wells (like oil and gas). It must be manufactured, and the process of making hydrogen requires energy. On an industrial scale that energy might come from conventional power stations, fueled by coal, oil or gas. So the emission of CO2 is transferred from the tailpipe of the car to the smokestack of the power station.

Where does that industrial energy come from?

Coal : The conventional view is that coal consists of old plant growth, compacted and geologically processed and concentrated over the ages. It is essentially a deposit of solar energy accumulated over geological time. We began to mine it only a few hundred years ago. At the present rate of consumption, it will last a few centuries, but probably not the millenium.

Oil and natural gas : These fuels, like coal, are extracted from geological deposits accumulated over eons. The conventional view is that gas and oil are biogenic like coal, but perhaps older. They have been exploited for a little over a hundred years; known reserves will last some few decades at the present rate of exploitation.

Renewable Energies : Some environmentalists are enthusastic about the coming era of  "renewable energies" by which they usually mean wind turbines and solar cells. Wind turbines capture the kinetic energy of the wind and convert it to mechanical and then electrical energy, while photovoltaic (PV) cells convert sunlight directly into electrical energy. In each case the electrical energy can be used to produce hydrogen gas by the electrolysis of water or by some other chemical process. Weingart has presented a systems analysis of a sustainable world-scale solar energy system, not neglecting to estimate such a system’s economic constraints and environmental impact(1). Others write enthusiastically of fields of wind turbines covering large areas (2).

But the sun doesn’t shine all the time and the wind doesn’t blow all the time, so some sort of energy storage is needed. Many systems use lead-acid batteries. But producing hydrogen for fuel cells would be another way to store that internittent energy. Furthermore, locations most suitable for wind turbines and PVs are often far away from industrial centers. Hydrogen production solves that problem too, for hydrogen can be transported from where it is produced to where it is used by pipeline or by cryogenic tank truck (3).

Renewable energies do indeed have their places in the palette of energy sources for the future, but it seems unlikely that they will ever be able to satisfy the voracious appetite of a modern industrial economy.

Distribution of hydrogen

No matter how it might be produced, hydrogen would be stored somehow and transported somewhere to be delivered to a fuel&endash;cell car where it would react with atmospheric oxygen producing water vapor and the electricity to power the car. There are various schemes for storage and transport - I’ll describe some below.

We speak nowadays of getting energy for our car at a filling station. We pump a tank of gas and burn it in our car with atmospheric oxygen and dump the exhaust, CO2, nitrogen oxides, etc., into the atmosphere. Cheap and dirty.

Suppose we fill up our fuel-cell car with hydrogen gas at a filling station. We would burn it with atmospheric oxygen in the fuel cell and release the resulting water vapor into the atmosphere. Clean! but perhaps not so cheap because we would have to create a new distribution system for hydrogen.

Hydrogen gas might be distributed to filling stations by pipeline and transferred to a sturdy tank in the car. The technology for handling gas at high pressure and releasing it a bit at a time is well developed. It might also be distributed by tank truck in the form of liquid hydrogen at very low temperature. Cryotechnology is a well developed technology - it’s a spinoff from high energy physics research and from space technology. Some satellite launchers are lifted off by booster rockets burning liquid hydrogen and liquid oxygen.

But some people don’t like the idea of having hydrogen gas around. Aside from the mechanical problems of storing it under high pressure or at low temperature, a mixture of hydrogen with air in certain proportions is explosive (but so are gasoline and cooking gas). Others worry about the practicalities of creating a new distribution system for hydrogen gas or liquid hydrogen. So other schemes are being developed to transport hydrogen more safely and conveniently.

Sequestration

Filling stations may become filling-and-emptying stations.

One such proposal consists of distributing methanol (CH3-OH) in filling stations. Methanol is a liquid and rich in hydrogen - all you need is another pump at the filling station. In this scheme methanol is "reformed" on board the car to liberate hydrogen gas for the fuel cell. But for each 10 litres of methanol you consume, you have about 3 kilograms of carbon left over.(4) You would store the carbon onboard your car, as a solid or powder, and empty it out when you fill up again at a roadside filling-and-emptying station. The carbon you empty out would be gathered up and returned somewhere to be got rid of; technically we call it sequestration. In other words, the production-and-distribution of methanol as fuel for a hydrogen fuel-cell car must be accompanied by the recovery-and-sequestration of the residual carbon.

In another such scheme, the carbon residue of the reformer is graphite powder. Graphite is totally inert and should not contaminate the biosphere. It might be dumped in a landfill or in the sea. Industrial uses might consume a small amount.

There are other schemes. In each case the hydrogen is chemically bound and released in an onboard reformer. The chemical residue must be taken care of - in some schemes it is sent back to the factory to be recycled and loaded up with hydrogen again.(5)

Big Numbers

At this point, it is convenient to begin to think quantitatively. Petroleum is transported across the seas in gigantic tankers of 100 000 tons, 250 000 tons and even 500 000 tons. Pipelines are much less spectacular than an oil tanker the size of a football field, but the quantities quietly transported by pipeline are similar. In the United States, coal is sometimes brought from the mine in "unit trains" composed of 100 cars, about a mile long, say 5000 tons a trainload. A 1000 Megawatt power plant will consume a trainload a day.

In the current oil crisis we learned that the world consumes about 70 million barrels a day, about 10 million tons a day, the contents of 20 to 50 gigantic oil tankers a day. Fortunately a substantial fraction of that oil is transported by pipeline. But we must deal with comparable amounts of carbon, perhaps in the form of graphite (about 8.5 million tons a day) or carbon dioxide (about 30 million tons a day).

In a recent year (1993) France consumed about 80 million tons of oil, about 220 000 tons (one giant tanker) a day. Burning that oil releases into the atmosphere about 190 000 tons of carbon per day. If all that carbon were sequestered as graphite, say, and carried away by train, it would fill ten thousand railroad cars; and the train would be a hundred kilometers long - every day (6).

(The useful power provided by that flow of oil is about 900 GWh. It is about the same as the power production of France’s 59 nuclear reactors.)

Now let's look briefly at nuclear power.

A nuclear power station emits no CO2, so if we make the hydrogen to run our fuel-cell cars by using electricity from a nuclear power station, then there is no emission of CO2.

Where does the uranium come from? Like everything else of which the Earth is composed, uranium is a remnant of a supernova (the explosion of a giant star) which occurred not far from here about five billion years ago, just before our solar system was formed. In fact, the entire solar system was formed of the debris of such stellar explosions. Uranium too is mined, and known mineral resources of uranium-235 will last a hundred years or so. With advanced reactor systems, thorium and uranium-238 can be converted to useful fuel and made to last fifty times longer.  (7, 8, 9)

For our purposes, the essential property of uranium as a source of energy is that it is compact - its energy density is about a million times greater than the energy density of fossil fuels. Thus for the same amount of energy, the volume of nuclear fuel is about a million times smaller than that of fossil fuel, and the volume of the end product is correspondingly a million times smaller.

In France 80% of the country's electricity is nuclear. In 1993, Électricité de France produced 368 188 GWh of nuclear electricity, about 1000 GWh per day. To produce that electrical energy, EdF consumed about 135 kilograms of U&endash;235 per day, about 50 tonnes per year (the U&endash;235 content of about 7000 tonnes of uranium - uranium is 99.3% U&endash;238 and only 0.7% U&endash;235). After fission, one is left with very nearly the same weight of radioactive waste. Most of the radioactivity is due to short&endash;lived fission products and spent fuel elements are allowed to "cool" for a few years on the site of the power station to permit that short&endash;lived radioactivity to decay. Only then does one chemically separate the long&endash;lived radioactive materials for sequestration, no more than 20 kilograms per day, say 7 tonnes per year.

It is generally agreed that long&endash;lived radioactive waste material should be permanently placed in deep geological repositories. Technical problems are on the way to solution, but there remain social and political problems associated with the identification of sites and their acceptance by the population surrounding, and with the surveillance of the repositories over periods of a few centuries. Nevertheless, I submit that it is much easier to separate and store nuclear fission products than to sequester the corresponding quantities of graphite, CO2, and whatever other residues may be derived from burning fossil fuels for our eventual hydrogen fuel-cell economy.

That explains in part why I am an environmentalist FOR nuclear energy.

Footnotes

* This article is a revision of a paper entitled " Nuclear power and the ‘hydrogen fuel-cell economy’ " submitted to FORESIGHT magazine (Colin R. Blackman, editor, Camford Publishing Company, Ltd., Sidney House, Sussex Street, Cambridge CB1 1PA United Kingdom ) in April 2001, and published in Volume 3, number 3, June 2001

(1) J. M. Weingart, "The Helios Strategy," Technological Forecasting and Social Change 12 (4), 1978. An extract appears in Richard Rhodes, Visions of Technology, Simon & Schuster, 1999, pp 323-8: "Operation of solar energy systems and the infrastructure required for their construction and replacement will have environmnetal consequences, in spite of some widely prevailing myths that solar technologies will be relatively benign. We know that new technology, when used on a large scale, will often have unexpected and sometimes unwanted consequences... Fragile desert ecosystems would be severely impacted during construction, with fine desert crust broken, leading to erosion and dust. The habitats of burrowing animals would be destroyed and the ecology of the region permanently altered. While on the national scale, additional air pollution resulting from production of glass, concrete and steel for the solar plants would not be substantial, the local impact of these emissions would constitute an environmental charge against the facilities." The time scale for reaching an industrial level is a century.

(2) Christopher Flavin and Nicholas Lenssen, "Power Surge: Guide to the Coming Energy Revolution" Worldwatch Institute,  Environmental Alert Series (1994).

(3) Henry R. Linden and S. Fred Singer, "A Carbon-Free Energy Future", a paper presented at a meeting of the American Geophysical Union, San Franciso, 12 December 2001

(4) Of course, you could burn it and release the CO2 into the atmosphere; but that’s almost as dirty as burning gasoline, and rather less efficient.

(5) Except for the quantities involved, recycling petroleum products is not an especially revolutionary idea. You change the lubricating oil in your motor from time to time; the old crankcase oil (5 liters at a time) is stored at your garage or service station and eventually collected and recycled for less critical uses.

(6) Spread out over the ground to a depth of one meter, the graphite so produced in France each year would cover about 35 square kilometers or 3500 hectares. For comparison, the area of the city of Paris is about 100 km2 .

(7) Known economic reserves of uranium are some tens of millions of tonnes. In the very long run, uranium might even be recovered from sea water where its concentration is 3 milligrams per cubic meter; there are about 4 billion tonnes of uranium dissolved in the seas [Robert H. Romer, "Energy Facts and Figures," Spring Street Press, Amherst MA (USA) (1985), p27]. The cost is estimated at ten times the current depressed price of uraniuim; but the cost of the nuclear fuel is a very small part of the price of nuclear electricity, so more expensive uranium would not much increase its price of a KWh of nuclear electricity.

(8) Romer has also pointed out (p44), that "(r)ocks containing low grade thorium deposits are found near the surface in many parts of the world. As an example, the Conway granites in New Hampshire (USA), covering an area of about 750 km2 and probably extending to a depth of several kilometers, contain 150 grams of thorium per cubic meter. The Conway granites down to a depth of one kilometer thus contain approximately [100 million tonnes] of thorium."

(9) In developing its as yet unannounced nuclear weapons program, and especially to be sure that it would be independent of foreign suppliers of uranium, Israel planned to fuel the Dimona plutonium production reactor with uranium extracted from abundant domestic phosphate deposits. Avner Cohen, "Israel and the Bomb," Columbia University Press, New York (1998), p179. Also A. Kossir and M. Lung, International WONUC Conference on Nuclear Desalination, Marrakesh, Morocco, 16-18 October 2002.

(about 2600 words)

© Berol Robinson Telephone: 01 46 26 02 05 (from France)

1, rue du Général Gouraud + 331 46 26 02 05 (from elsewhere)

F-92190 MEUDON, France eMail: berol[at]ecolo.org

The writer is an American nuclear physicist and environmentalist. He is a retired senior science officer of UNESCO headquarters in Paris and he resides in France. He is a member of the Scientific Committee of the international Association of Environmentalists For Nuclear Energy; website http://www.ecolo.org.

Association of Environmentalists For Nuclear Energy

55, rue Victor Hugo, F-78800 Houilles, France

Telephone: + 33 1 30 86 00 33; Fax: + 33 1 30 86 00 10

eMail: EFN[at]ecolo.org