An Edible History of Humanity (22 page)

In a speech at the annual conference of the British Association for the Advancement of Science in 1898, William Crookes, an
English chemist and the president of the association, highlighted the obvious solution to the problem. A century after Thomas
Malthus had made the same point, he warned that “civilised nations stand in deadly peril of not having enough to eat.” With
no more land available, and with concern growing over Britain’s dependence on wheat imports, there was no alternative but
to find a way to increase yields. “Wheat preeminently demands nitrogen,” Crookes observed. But there was no scope to increase
the use of manure or leguminous plants; the supply of fertilizer from coal was inadequate; and by relying on Chilean nitrate,
he observed, “we are drawing on the Earth’s capital, and our drafts will not perpetually be honoured.” But there was an abundance
of nitrogen in the air, he pointed out—if only a way could be found to get at it. “The fixation of nitrogen is vital to the
progress of civilised humanity,” he declared. “It is the chemist who must come to the rescue . . . it is through the laboratory
that starvation may ultimately be turned into plenty.”

In 1904 Fritz Haber, a thirty-six-year-old experimental chemist at the Technische Hochschule in Karlsruhe, was asked to carry
out some research on behalf of a chemical company in Vienna. His task was to determine whether ammonia could be directly synthesized
from its constituent elements, hydrogen and nitrogen. The results of previous experiments had been unclear, and many people
thought direct synthesis was impossible. Haber himself was skeptical, and he replied that the standard way to make ammonia,
from coal, was known to work and was the easiest approach. But he decided to go ahead with the research anyway. His initial
experiments showed that nitrogen and hydrogen could indeed be coaxed into forming ammonia at high temperature (around 1,000
degrees Centigrade, or 1,832 degrees Fahrenheit) in the presence of an iron catalyst. But the proportion of the gases that
combined was very small: between 0.005 percent and 0.0125 percent. So although Haber had resolved the question of whether
direct synthesis was possible, he also seemed to have shown that the answer had no practical use.

And there things might have rested, had it not been for Walther Hermann Nernst, another German chemist, who was professor
of physical chemistry at Göttingen. Although he was only four years older than Haber, Nernst was a more eminent figure who
had made contributions in a number of fields. He had invented a new kind of light bulb, based on a ceramic filament, and an
electric piano with guitar-style pickups, though neither was a commercial success. Nernst was best known for having proposed
a “heat theorem” (now known as the third law of thermodynamics) in 1906 that would win him the Nobel prize in Chemistry in
1920. This theorem could be used to predict all sorts of results, including the proportion of ammonia that should have been
produced by Haber’s experiment. The problem was that Nernst’s prediction was 0.0045 percent, which was below the range of
possible values determined by Haber. This was the only anomalous result of any significance that disagreed with Nernst’s theory,
so Nernst wrote to Haber to point out the discrepancy. Haber performed his original experiment again, obtaining a more precise
answer: This time around the proportion of ammonia produced was 0.0048 percent. Most people would have regarded that as acceptably
close to Nernst’s predicted figure, but for some reason Nernst did not. When Haber presented his new results at a conference
in Hamburg in 1907, Nernst publicly disputed them, suggested that Haber’s experimental method was flawed, and called upon
Haber to withdraw both his old and new results.

Haber was greatly distressed by this public rebuke from a more se-nior scientist, and he suffered from digestion and skin
problems as a result. He decided that the only way to restore his reputation was to perform a new set of experiments to resolve
the matter. But during the course of these experiments he and his assistant, Robert Le Rossignol, discovered that the ammonia
yield could be dramatically increased by performing the reaction at a higher pressure, but a lower temperature, than they
had used in their original experiment. Indeed, they calculated that increasing the pressure to 200 times atmospheric pressure,
and dropping the temperature to 600 degrees Centigrade (1,112 degrees Fahrenheit), ought to produce an ammonia yield of 8
percent—which would be commercially useful. The dispute with Nernst seeemed trivial by comparison and was swiftly forgotten,
and Haber and Le Rossignol began building a new apparatus that would, they hoped, produce useful amounts of ammonia. At its
center was a pressurized tube just 75 centimeters tall and 13 centimeters in diameter, surrounded by pumps, pressure gauges,
and condensers. Haber refined his apparatus and then invited representatives of BASF, a chemical company that was by this
time funding his work, to come and see it in operation.

The crucial demonstration took place on July 2, 1909, in the presence of two employees from BASF, Alwin Mittasch and Julius
Kranz. During the morning a mishap with one of the bolts of the high-pressure equipment delayed the proceedings for a few
hours. But in the late afternoon the apparatus began operating at 200 atmospheres and about 500 degrees Centigrade, and it
produced an ammonia yield of 10 percent. Mittasch pressed Haber’s hand in excitement as the colorless drops of liquid ammonia
began to flow. By the end of the day the machine had produced 100 cubic centimeters of ammonia. A jubilant Haber wrote to
BASF the next day: “Yesterday we began operating the large ammonia apparatus with gas circulation in the presence of Dr. Mittasch
and were able to keep its production uninterrupted for about five hours. During this whole time it functioned correctly and
it continuously produced liquid ammonia. Because of the lateness of the hour, and as we all were tired, we stopped the production
because nothing new could be learned from continuing the experiment.”

Ammonia synthesis on a large scale suddenly seemed feasible. BASF gave the task of converting Haber’s benchtop apparatus into
a large-scale, high-pressure industrial process to one of its senior chemists, Carl Bosch. He had to work out how to generate
the two feedstock gases (hydrogen and nitrogen) in large quantities and at low cost; to find suitable catalysts; and, most
difficult of all, to develop large steel vessels capable of withstanding the enormous pressures required by the reaction.
The first two converters built by Bosch, which were around four times the size of Haber’s apparatus, failed when their high-pressure
reaction tubes exploded after around eighty hours of operation, despite being encased in reinforced concrete. Bosch realized
that the high-pressure hydrogen was weakening the steel tubes by depleting them of the carbon that gives steel its strength
and resilience. After much trial and error he redesigned the inside of the tubes to prevent this problem. His team also developed
new kinds of safety valves to cope with the high pressures and temperatures; devised clever heat-exchange systems to reduce
the energy required by the synthesis process; and built a series of small converters to allow large numbers of different materials
to be tested as possible catalysts. Bosch’s converters gradually got bigger during 1910 and 1911, though they were still producing
only a few kilograms of ammonia per day. Only in February 1912 did output first exceed one ton in a single day.

By this time Haber and BASF were under attack from rivals who were contesting Haber’s patents on the ammonia-synthesis process.
Chief among them was Walther Nernst, whose argument with Haber had prompted Haber to develop the new process in the first
place. Some of Haber’s work had built on earlier experiments by Nernst, so BASF offered Nernst an “honorarium” of ten thousand
marks a year for five years in recognition of this. In return, Nernst dropped his opposition to Haber’s patents, and all other
claims against Haber were subsequently thrown out by the courts.

Meanwhile ever-larger converters, now capable of producing three to five metric tons a day, were entering service at BASF’s
new site at Oppau. These combined Haber’s original methods with Bosch’s engineering innovations to produce ammonia—from nitrogen
in the air, and hydrogen extracted from coal—using what is now known as the Haber-Bosch process. By 1914 the Oppau plant was
capable of producing nearly 20 metric tons of ammonia a day, or 7,200 metric tons a year, which could then be processed into
36,000 metric tons of ammonium sulphate fertilizer. But the outbreak of the First World War in August 1914 meant that much
of the ammonia produced by the plant was soon being used to make explosives, rather than fertilizer. (Germany’s supply of
nitrate from Chile was cut off after a series of naval battles, in which the British prevailed.)

The war highlighted the way in which chemicals could be used both to sustain life or to destroy it. Germany faced a choice
between using its new source of synthetic ammonia to feed its people or supply its army with ammunition. Some historians have
suggested that without the Haber-Bosch process, Germany would have run out of nitrates by 1916, and the war would have ended
much sooner. German production of ammonia was scaled up dramatically after 1914, but with much of the supply being used to
make munitions, maintaining food production proved to be impossible. There were widespread food shortages, contributing to
the collapse in morale that preceded Germany’s defeat in 1918. So the synthesis of ammonia prolonged the war, but Germany’s
inability to produce enough for both munitions and fertilizer also helped to bring about the war’s end.

Haber himself strikingly embodies the conflict between the constructive and destructive uses of chemistry. During the war
he turned his attention to the development of chemical weapons, while Bosch concentrated on scaling up the output of ammonia.
Haber oversaw the first successful large-scale use of chemical weapons in April 1915, when Germany used chlorine gas against
the French and Canadians at Ypres, causing some five thousand deaths. Haber argued that killing people with chemicals was
no worse than killing them with any other weapon; he also believed that their use “would shorten the war.” But his wife, Clara
Immerwahr, who was a chemist herself, violently disagreed, and she shot herself using her husband’s gun in May 1915. Scientists
of many nationalities protested when Haber was awarded the 1918 Nobel prize in Chemistry, in recognition of his pioneering
work on the synthesis of ammonia and its potential application in agriculture. The Royal Swedish Academy of Sciences, which
awarded the prize, commended Haber for having developed “an exceedingly important means of improving the standards of agriculture
and the well-being of mankind.” This was a remarkably accurate prediction, given the impact that fertilizers made using Haber’s
process were to have in subsequent decades. But the fact remains that the man who made possible a dramatic expansion of the
food supply, and of the world population, is also remembered today as one of the fathers of chemical warfare.