While in graduate school I learned that the computer had applications beyond physics. In their jarring book Limits to Growth, Donella Meadows and her coworkers at MIT used innovative numerical simulations to predict Malthusian scenarios scheduled to debut at the beginning of the 21^st century. Their predictions became the subject of heated discussions both inside and outside the classroom. Unknown to many of us at that time, more than a decade prior to the publication of Limits to Growth, M. King Hubbert of the U.S. Geological Survey had used numerical models based on solutions of the logistics equation to predict the year that U.S. oil production would peak. Hubbert’s prediction proved to be true. Moreover, the year of publication of Limits to Growth nearly coincided with the peak in U.S. oil production. Fortunately for us now, the predictions of Donella Meadows and her coworkers were less reliable than the projections of M. King Hubbert.

In spite of these disturbing mathematical prognostications, young physicists like myself could feel some optimism about the future. Nuclear energy promised power "too cheap to meter" (prior to the event at Three Mile Island), thermonuclear energy seemed to be just around the corner, and prescient futurists proclaimed the hydrogen economy as the panacea for all problems associated with fossil fuels and their environmental impacts. At that time the Los Alamos Scientific Laboratory (LASL) was a hotbed of research in nuclear and hydrogen energy (high-temperature gas-cooled nuclear reactors suited for producing hydrogen by thermochemical water splitting cycles), as well as nuclear fusion (especially laser fusion) research. I was delighted when Los Alamos offered me a position in its thermonuclear weapons physics group. My first job was to develop software to simulate fast charged particle transport in thermonuclear plasmas by numerical solution of the Boltzmann equation. The addition of my software to existing code caused the package to exceed the storage limits of the most powerful computers of that era. A computer simulation ran all night and its output was studied for days thereafter.

There were no serious shortages of gasoline at Los Alamos during the "first energy crisis" of 1973. In my free time I followed the energy literature and was deeply impressed by an article in Science concerning the magnitude of the renewable American biomass resource. My reading led me to conclude that renewable hydrogen could be produced from biomass by a steam reforming process similar to that used in the manufacture of hydrogen from methane. During the winter of 1974, I obtained special permission to attend the first international meeting on Hydrogen Energy that was organized and chaired by Dr. Mel Bowman, who was then Associate CMB Division Leader. A few months later I garnered significant support from the U.S. Environmental Protection Agency to pursue my ideas on hydrogen production from biomass in collaboration with my colleague Dr. Bowman. For about six months I devoted my mornings to thermonuclear weapons physics research, and my afternoons to chemical engineering activities centered on hydrogen production by the thermochemical gasification of biomass. Unfortunately, the leadership of Los Alamos was not comfortable with my widespread interests, and they made their disapproval known to me. I was glad when Princeton University offered me a tenure-track position in the energy sciences within its Department of Mechanical and Aerospace Engineering. I took a part of my EPA sponsored research program with me to Princeton when I left Los Alamos in 1975.

At Princeton, Dr. Martin Summerfield enjoyed an international reputation for his work in solid rocket fuel propellants. I was fortunate that he offered me space in his laboratory to pursue my research. As a result of my interactions with him, his staff, and his students, I realized the need to understand the effects of temperature, pressure, and heating rate on the products of biomass pyrolysis and gasification. Furthermore, I needed a fundamental understanding of both solid phase and gas phase transformations. In collaboration with Dr. Henry Friedman—a past President of the North American Thermal Analysis Society—my students and I employed thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to study the pyrolytic behavior of whole biomass substrates (e.g., oak wood) and representative model compounds (e.g., cellulose and levoglucosan). Likewise, Dr. Maitland Jones, Jr.—author of a highly regarded organic chemistry textbook and one of Princeton’s most beloved professors—generously worked with me and my students to develop a better understanding of the gas phase pyrolysis behavior of tarry vapors and their model compounds (e.g., 1,3 dioxolane and glycerol). I also developed an interest in chemical applications of high temperature solar energy. Research projects in this field took me to the 1 MW_th solar furnace in the French Pyrenees, and a smaller furnace on the Georgia Tech campus. Unfortunately, some of the senior faculty in my department—and their corporate sponsors—strongly disapproved of my interests. They felt that I should focus my attention on shale oil and other fossil fuels. This conflict was resolved when the University of Hawaii (UH) received an unexpected gift of $800,000 from the Texas oil magnate David Chalmers to endow a Chair in Renewable Energy. I was delighted to accept the Coral Industries Chair of Renewable Energy Resources when it was offered to me in the spring of 1981, and I moved my laboratory and students to the Manoa campus on 1 January 1982.

During my last year at Princeton, I had a memorable experience. The editor of a widely read journal of the middle-Atlantic states asked me to write a feature article on renewable energy. I was promised a substantial honorarium. To ensure that I was on the right track, I sent installments of the article as I wrote it to an assistant editor for his review. Each installment was greeted with enthusiasm and compliments. I concluded the article with the prediction that soon the USA would be forced to fight wars over oil in the Mideast if it did not develop renewable alternatives. The editor of the journal did not like my conclusion, and demanded that I rewrite it. Dutifully I deleted all unpleasant references to war and the urgent need for energy conservation, but my faux pas in the first draft had poisoned the well: the editor refused to publish my article.

During the following two decades my work at UH matured and came to focus on four principal fields of application.

1. Hydrogen from biomass. My initial interest at Los Alamos in the steam reforming of biomass evolved into studies of biomass gasification in supercritical water. We learned that carbon catalysts enabled the complete gasification of biomass feedstocks in supercritical water. Furthermore, the gas was unusually rich in hydrogen, and available at a very high pressure. But an economic prognosis by the National Renewable Energy Laboratory (NREL) indicated that hydrogen produced by our process would cost more than four times the current cost of oil, and funding for this work ceased. Nevertheless, my former student, Professor Yukihiko Matsumura of the University of Hiroshima, together with another former student, Dr. Tomoaki Minowa of AIST in Japan, organized an international research effort including workers from the Netherlands and the USA on this topic. Furthermore, following my lead German researchers at the Forschungszentrum Karlsruhe built a pilot plant ("VERENA") to demonstrate supercritical water gasification of biomass. Unfortunately, recently the Japanese have confirmed the dismal economics of the process, and the Germans have encountered difficult engineering hurdles in their work.
2. Ethanol from lignocellulosic biomass. Our work with supercritical water led us to the unexpected discovery that all of the hemicellulose and about half of the lignin in lignocellulosic biomass dissolves during a one to two minute exposure to liquid water at 220 ºC. Working with Professor Lee Lynd at Dartmouth College—an internationally recognized authority on fermentations—we showed that the cellulosic residual of our hot liquid water pretreatment was very well suited for enzymatic saccharification followed by fermentation to ethanol. The yields of ethanol obtained by Professor Lynd and his students were among the highest ever reported. Late last year NREL announced that hot liquid water appears to be the most attractive pretreatment process for ethanol production. Nevertheless, NREL estimates that a commercial ethanol from biomass refinery will cost more than $300 million.
3. Chemicals from biomass. The novel acid- and base-catalyzed reactions of sugars and fermentation products in hot liquid, and supercritical water seemed to offer opportunities to produce a variety of desired chemical building blocks from biomass. With Professor Geoffrey Richards of the University of Montana—a winner of the Anselme Payen Award of the American Chemical Society—we shed new light on the reactions that form furfural from xylose and hydroxymethyl furfural from glucose, fructose, and sucrose. Similarly, with Maitland Jones we examined reactions that form acrylic acid from lactic acid, and methacrylic acid from citric acid. During the academic year 1990-91, Dr. Donald G. M. Anderson, Gordon McKay Professor of Applied Mathematics at Harvard, hosted my sabbatical, and together we developed detailed, mechanistic kinetic models of the acid-catalyzed formation of ethene from ethanol, propene from 1- and 2-propanol, and butene from tert-butanol.
4. Carbon from biomass. The MSE thesis of my student William Mok at Princeton showed that increasing pressure strongly favors the formation of carbon (charcoal) from biomass during pyrolysis. His work with DSC and TGA continued via collaborations with Dr. Gabor Varhegyi of the Research Laboratory of Materials and Environmental Chemistry of the Hungarian Academy of Sciences, and Dr. Morten Gronli of the Norwegian Technological University. Results of these fundamental studies became the foundation of an effort to dramatically improve the efficiency of charcoal production. We built a pilot plant whose charcoal yields attained the limit set by thermodynamics with a reaction time of about 70 minutes. This work was patented and licensed, but a Kingsford engineer complained to us about the energy input. Two years ago his complaint caused me to initiate work on a pressurized, downdraft biomass "gasifier" that would be operated to quickly produce high yields of carbon from biomass. This "flash carbonization" process has been successful beyond our wildest dreams. Yields of carbon equal or exceed those of the high-yield charcoal process, and reaction times have been reduced to as little as 20 minutes. The UH has applied for patents on flash carbonization and has already licensed it. We anticipate that the production biomass carbons will eclipse that of fossil carbons (coal) and will find many new applications. For example, one current focus of my research is the development of a biocarbon fuel cell (a "battery" that generates electricity by the electrochemical oxidation of charcoal).

While at Princeton I invited M. King Hubbert to speak on his work. During his seminar he used the same mathematical models that had successfully predicted the peak of oil production in the USA to predict that world oil production would peak shortly after the turn of the century. Recently, Professor Kenneth S. Deffeyes (also of Princeton) updated and refined the models of M. King Hubbert. In his widely read book Hubbert’s Peak, Deffeyes predicts that the peak in world oil production will occur next year. I am aware of much evidence that corroborates his prediction. The adjustments that will be required as demand for oil exceeds supply, following the peak in world oil production, are beyond my ability to comprehend. I hope that mankind’s progress in the development of renewable energy will not be too little, too late.

In conclusion I thank my students, coworkers, and collaborators—many of whom could not be mentioned in this essay because of space limitations—for their inspiration and friendship. My work would not have been possible without them.

Michael Jerry Antal, Jr., Ph.D.
School of Ocean Earth Science & Technology
University of Hawaii, Manoa
Oahu, Hawaii, USA