Letters

Sailing on solar

Your editorials about energy and energy policy prompted me to revisit a letter I wrote a while ago to Scientific American in reaction to an energy policy editorial in that magazine (C&EN, March 15, page 3; March 22, page 3). A substantial R&D agenda and very large investments are needed, but no fundamental breakthroughs are necessary.

It should be clear as day that the only sustainable energy source for the planet is solar. Any other form is hopelessly dirty in some aspect or another and is limited.

Luckily, the sun sends an overabundance of energy our way and hasn’t had one day of downtime for eons. Harvesting that energy in an efficient manner will require a vast further R&D effort and a large investment—that is, many jobs need to be filled. Very large desert areas are waiting to be turned into solar energy plants, as are many roofs.

The form of such solar energy will be electricity and heat, which is excellent for sedentary applications (a large fraction of the total), but not for many forms of transportation. It is common knowledge that electricity is equivalent with hydrogen in a clean process. Hydrogen is not a manageable transportation fuel, though. So, will we have to do without convenient motor vehicles?

Help (again, from the sun) is at hand to make transportation fuels using conventional technology. The sun powers the synthesis of vast amounts of cellulose (trees, bamboo, et cetera), and the rate of production (about 75 billion tons per annum) dwarfs the amounts of petroleum and other fossil fuels extracted from the earth. It also dwarfs the production of food crops.

Wet cellulose has the formula (CHOH)_n, which is equivalent to CO + H₂, which is often made from coal and water and called “synthesis gas” in the chemical industry.

It is not so hard, then, to convert wood into synthesis gas and ashes (that is, the inorganics that should be returned to the earth to help new wood to grow). During World War II, many cars in Nazi-controlled Europe were powered by “wood gas” generated by heating wood in a device mounted to the vehicle.

Such synthesis gas with an extra addition of hydrogen is currently converted into methanol in large-scale industrial processes. Methanol is a convenient motor fuel and has ample energy density for powering land and sea vehicles with existing engine technology. Processes have also been invented to convert methanol into gasoline-type fuels showing almost double the energy density, which is desirable for aviation, where weight is at a premium.

Note that we need not “power the earth with wood,” only the transportation sector with “wood plus hydrogen.” Refocusing this country’s problem-solving resources toward sustainable modes of inhabiting the planet is long overdue.

Doetze J. Sikkema
Richmond, Va.

Nanotech challenge

The recent publication of an additional letter to the editor (C&EN, May 17, page 5) regarding the Nanotechnology Point/Counterpoint (C&EN, Dec. 1, 2003, page 37) suggests that readers are still interested in this exchange.

To date, although I’ve heard of scientists who endorse Richard E. Smalley’s conclusions, none has been willing to endorse the core of his new argument (that water is essential to controlled chemical synthesis). Some of the earlier letters to the editor instead repeated old speculations that a thermodynamic limit might preclude precise molecular manufacturing, but this argument would speak with similar force against the existence of crystals and living systems. Design studies in this area fully reflect such basic principles as the atomicity of matter and the laws of thermodynamics, and the rest of chemistry and physics besides.

Given the ongoing interest in this topic, I (and my colleagues) would welcome an opportunity to respond to informed criticism of the published literature on molecular manufacturing. If the opponents to molecular assemblers can point to specifics and elevate the discussion to one of physics and engineering, this dialogue would present a key breakthrough regarding open, productive discussion of these important issues. Indeed, if our arguments are faulty, this discussion would put an end to such questions in a decisive manner. Otherwise, it appears the questions will center on graphical display conventions.

If no opponents present themselves, then perhaps an article covering recent and past progress in mechanosynthetic modeling would advance the discussion.

K. Eric Drexler
Palo Alto, Calif.

Mad about mad cow

Your article “Mad Cow Disease” is comprehensive and very well presented (C&EN, May 31, page 21). The uncertainties cited, both scientific and regulatory, argue not for further cautious stepwise actions based upon the meat industry’s cost fears, but for much more aggressive, if not universal, testing. If that turns out not to be truly necessary, restrictions could be relaxed later. But we’d all be much better off with a “better safe than sorry” approach, as advocated by scientists with Nobel or other prizes rather than accountants and lobbyists. At a minimum, any producer who wishes to test should be able to do so.

For more details, see our editorial “Remedy for an insane policy—Test all beef for mad cow” in the May 14 San Francisco Chronicle.

Steve Heilig
San Francisco

Stanley B. Prusiner used an analogy: If there were two ticket lines at an airport and one guaranteed you would get to your destination safely for $1.00 extra while the other line offered no such guarantee, most consumers would pay the extra dollar. Similarly, he expects that most consumers would be willing to pay a few extra cents per pound for BSE-tested beef.

I think this is a near perfect analogy, hampered only by the fact that a few cents per pound of beef would equate to more like an extra $20 for the air trip safety guarantee.

Nonetheless, I think he’s right; most customers would probably choose it. As in his analogy, the key should be to let the market decide that. Allow producers to fully test if they like, or spot test if they like, and let consumers choose which they prefer.

This is immediately implementable and requires no additional laws, regulations, or bureaucrats. Just step back and let the market handle it. The only legal ramification would be continued normal enforcement of false advertising laws if any producer were found to be claiming full testing without actually performing it.

Philip Boncer
San Diego

Global call to arms

Kudos to Jurgen H. Exner for his comment “Global Climate Change and Citizen Chemists” (C&EN, March 29, page 45). He asks us to learn the issues, talk to others about them, write to our newspapers urging the government to invest in enhanced energy efficiency and conservation, save energy in our homes and factories, and choose fuel-efficient cars. In the long term, he says, the debate will be settled through science; we must embrace technologies that help us mitigate the potential negative effects of climate change.

These are all good things, but they will not happen automatically; we must demonstrate our support of them—long, loud, and often. Exner renders a real service in calling for individuals to exercise the rights and duties of citizens. Maybe then the issue will be settled by science. What we should fear most is that it will be settled by inaction, which is really all it takes for the status quo to prevail.

Exner’s most telling call may be to “embrace technologies that can help us to mitigate the potential negative aspects of climate change.” The scientific community today seems to be fixed on the reduction of CO₂ emissions as the only path to control the CO₂ level in the atmosphere, a very significant element of global climate change. Stabilization has been approached as a removal problem, resulting in very low cost methane and concentrated carbon forms suitable for segregation to achieve stability. This technology has been published over a number of years; only techniques already in use and well understood are required.

There may be other approaches to the control problem that are left out of consideration because of this seeming bias, and Exner exhorts us not to neglect them. Let us hope that his urging succeeds.

H. A. Hartung
Collingswood, N.J.

Feedstock fix

The article “Biomass or Bust” provided a thought-provoking update for those of us who have an abiding interest in this promising area (C&EN, May 31, page 31).

A paper titled “Chemicals from Biomass: Petrochemical Substitution Options” [Science, 212, 1465 (1981)] is relevant to the following discussion of chemical feedstocks. The nomenclature of that article is based on a hierarchy that goes from resources (for example, grains) to feedstocks (for example, starch) to primary chemicals (for example, glucose) to intermediates (for example, sorbitol), and so on. There are advantages in showing the whole system because of multiple routes to the key building blocks and from them to the key chemical and end-use markets.

The new Department of Energy study uses a different nomenclature from the 1981 study because it is focused on the plant sugars part of the system. However, the Top 12 top-tier building blocks list that is shown in the “Building Blocks” chart (page 32) contains some intermediate chemicals. Two of the “key feedstocks” are derived from a third feedstock that is not on the list. That is, 5-hydroxymethyl furfural (5-HMF) is the building block from which 2,5-furandicarboxylic acid and levulinic acid are derived.

If 5-HMF is added to the feedstock list, and levulinic acid and 2,5-furandicarboxylic acid are removed, the top-tier building blocks list is improved. 5-HMF is also the parent of several other potentially useful intermediate chemicals (2,5-dihydroxymethylfuran, 2-hydroxymethyl-5-furoic acid, and the corresponding tetrahydrofuran products). In other words, there is a family of intermediate chemicals that are made from glucose via the building block named 5-HMF.

Thus, the Top 12 list becomes a Top 11 list. If 12 candidates for the list are still desired, the C&EN article mentions lactic acid, a candidate that has the indubitable advantage of commercialization by determined developers.

Edward S. Lipinsky
Worthington, Ohio

To bee or not to bee

It is disingenuous to claim that pesticides have gotten a bum rap for Europe’s declining honeybee population merely because the bee colonies are being killed by the varroa mite (C&EN, April 19, page 16).

Could it be that the mite is given a competitive advantage by Fipronil killing wireworm and other pests in the soil? Does the Fipronil in the soil persist? Is it carried up the food chain? Are other pesticides responsible? Is the answer really to create or use more pesticides (Perizin) to kill the mites? Surely expert environmental biologists will have more to say on the subject.

Felicia Etzkorn
Blacksburg, Va.