CHAPTER 4 - Gleanings from SCIENCE, Aug 13, 2004

No sooner was I back at my office at the University of Wisconsin than I read the front cover of SCIENCE magazine, published weekly by the American Association for the Advancement of Science. It was a special issue, mostly devoted to “Toward a Hydrogen Economy”. It turned out to be the second part of a “1-2 punch” that sent me spinning into a whole new orbit of thought.

The editors of that special issue, Robert Coontz and Brooks Hanson, wrote a very clear introduction, entitled “Not So Simple”, in which they pointed out that, while hydrogen atoms are common on earth, they are eager to bond, so they are very rare in unattached form. Releasing them requires breaking chemical bonds, and that requires energy. Once released, the atoms pair up into two-atom molecules, becoming a light, invisible gas that is hard to store, transport, liquefy or handle safely. Don Kennedy, the Editor-in Chief for SCIENCE, went on to explain that glib announcements of the Hydrogen Fuel Initiative and FreedomCAR Part-nership by the Bush administration, while politically useful, leave America spewing one quarter of the world’s 6.5 billion tons of carbon into the atmosphere in a “business as usual” stance for the foreseeable future. Because the amount of CO2 added [by us] exceeds the amount removed [by Nature], the concentration of atmospheric CO2 continues to increase annually, and the added carbon remains in the atmosphere for decades. Even if all nations on the planet stabilized our release of CO2 emissions to steady-state, the concentration of “greenhouse” gases would continue to rise for the rest of the century, and the average global temperature would increase in response. The severity depends on how quickly we act.

The utility of this particular issue of “SCIENCE” was in the selection of topics that surround the hydrogen economy issue. The first article, entitled: “The Hydrogen Backlash”, by Robert Service, warned that transition to a hydrogen economy, if it comes at all, won’t happen soon, perhaps not until the second half of the century. Each of the problems to be solved, - production, storage, fuel cell cost, safety and infrastructure – would be difficult enough on its own, but to solve them simultaneously, as would be required for success, would be extremely unlikely. A chemical engineer at MIT was quoted as saying, “The hype has been way overblown. It’s just not thought through.” To combat the warming threat, funding agencies should place a near-term priority on promoting energy efficiency, renewable research, and development of hybrid cars.

The second article, also written by Robert Service, was aptly titled “The Carbon Conundrum”. The theme here was that even if the hydrogen economy were technically and economically feasible today, weaning the world off carbon-based fossil fuels would still take decades. During that time, carbon combustion would continue to pour greenhouse gases into the atmosphere – unless scientists find a way to capture and store or sequester unwanted carbon dioxide.

Although no-one has adapted this strategy on a large scale, it just happens that oil companies have been piping CO2 underground for decades, in order to extract more oil from wells by reducing the viscosity of under-ground oil. Until 10 years ago, companies didn’t bother to track whether the CO2 remained underground or caused unwanted side effects. More recently energy specialists began to realize that storing CO2 underground into depleted oil and gas reservoirs may be the least harmful solution, albeit short-term, for storing unwanted CO2.
At first, it sounded like a wild idea, partly because the volume of gas that would have to be stored is enormous. For example, storing just 1 Gigaton of CO2 – about 48% of what we vent every year around the globe – would require moving 4.8 million cubic meters of CO2 a day. (That is equivalent to about one third of the volume of all the oil shipped daily around the globe!) But preliminary studies suggest that there is enough underground capacity to store hundreds of years’ worth of CO2 injection, and potential storage sites exist worldwide.

To test the technical feasibility of this strategy, researchers are teaming up with oil and gas companies to study their CO2 piping projects. One of the first to be studied is in Saskatchewan, Canada, where EnCana has launched a $1.5 billion, 30-year effort to pipe 20 million metric tons of CO2 into their reservoir. This is not pure altruism, since EnCana hopes this will increase the yield of their field by another third. (They simply use compressors to force compressed CO2 down a long pipe drilled into the underground reservoir.) So far, over 5 years, they have locked away nearly 3.5 million metric tons of CO2 in the Weyburn reservoir.

There are several other equally well-written viewpoints in that special issue of “SCIENCE”, but the review article by S. Pacala and R. Socolow (10) is especially relevant. They have written a prescription for the future, so it resembles Plan B, except that it is aimed specifically at the problem of global warming. Their key point is: we already possess the fundamental scientific, technical and industrial know-how to solve the carbon and climate problem for the next half-century. By applying a portfolio of existing technologies to meet the world’s energy needs over the next 50 years, we can limit atmospheric CO2 accumulation to a lower trajectory that might avoid otherwise devastating effects.

The first of 15 strategies discussed in this review is the use of efficient vehicles. Let us suppose that the world’s fleet of cars and trucks expands by ~4-fold over the next 50 years to 2 billion units. Without a focus on carbon we might improve our fuel economy to an average of 30 miles per gallon (mpg). However, with the use of hybrid vehicles it is now possible to achieve 60 mpg, and future advances should allow us to bring the entire global fleet to that level over the next 50 years. If we accomplished this goal by 2055, we would reduce the carbon emission rate by 1 gigaton per year, or by 25 gigatons over 50 years.

Such large numbers as gigatons of carbon are difficult to grasp conceptually. To fully appreciate the value of automobile efficiency, consider these statistics: Improving the efficiency of the automotive fleet - just in USA – by 1 mpg would save twice the amount of oil that could ever be harvested from ANWR (Arctic National Wildlife Reserve). Further improvement by 8 mpg would avoid our need to import oil from any Arabian gulf country. Future enlargements of the global car fleet will come primarily from China and India, where hybrid technology can be employed very effectively.

A second strategy would be to persuade people to reduce vehicle use from an average of 10,000 miles/year to 5,000 miles/year. This will require altruism from people who are already quite addicted to the “freedom” of individual travel in automobiles. However, increased traffic congestion and/or gasoline taxes may motivate more people to use mass transit. Other gains can be achieved from telecommuting and from improving urban design to promote walking instead of driving.

The remaining 13 strategies are equally important, but they require leadership from all of our elected officials. They include: use of more efficient heating and cooling in buildings and appliances, use of less fossil fuels and more sustainable fuels in our power plants, and the capture and underground storage of CO2 in empty oil and gas fields until we can be weaned off the use of fossil fuels entirely. This will require the installation of millions more wind turbines and photovoltaic power units, and perhaps, if absolutely necessary, some nuclear power plants as well. All this would be aided if we could stop tropical deforestation and plant new trees. Most important, the longer we delay to take these actions, the more difficult the transition will be (11).


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