by Tom Standage
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.
Fritz Haber’s experimental apparatus.
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.)
Carl Bosch.
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.
When scientists in Britain and other countries had tried to replicate the Haber-Bosch process themselves during the war, they had been unable to do so because crucial technical details had been omitted from the relevant patents. These patents were confiscated after the war, and BASF’s plants were scrutinized by foreign engineers, leading to the construction of similar plants in Britain, France, and the United States. During the 1920s the process was refined so that it could use methane from natural gas, rather than coal, as the source of hydrogen. By the early 1930s the Haber-Bosch process had overtaken Chilean nitrates to become the dominant source of artificial fertilizer, and global consumption of fertilizer tripled between 1910 and 1938. Having relied on soil microbes, legumes, and manure for thousands of years, mankind had decisively taken control of the nitrogen cycle. The outbreak of the Second World War prompted the construction of even more ammonia plants to meet the demand for explosives, which meant that there was even more fertilizer-production capacity available after the war ended in 1945. The stage was set for a further dramatic increase in the use of artificial fertilizer. But if its potential to increase food production was to be exploited to the full, new seed varieties would also be needed.
THE RISE OF THE DWARFS
The availability of artificial fertilizer allowed farmers to supply much more nitrogen to their crops. For cereals such as wheat, maize, and rice, this produced larger, heavier seed heads, which in turn meant higher yields. But now that they were no longer constrained by the availability of nitrogen, farmers ran into a new problem. As the use of fertilizer increased the size and weight of the seed heads, plants became more likely to topple over (something farmers call “lodging”). Farmers had to strike a balance between applying plenty of fertilizer to boost yield, but not so much that the plants’ long stalks were unable to support the seed heads. The obvious solution was to switch to short, or “dwarf” varieties with shorter stalks. As well as being able to support heavier seed heads without lodging, dwarf varieties do not waste energy growing a long stalk, so more energy can be diverted to the seed head. They therefore boost yield in two ways: by allowing more fertilizer to be applied, and by turning applied nutrients more efficiently into useful grain, rather than useless stalk.
During the nineteenth century, dwarf varieties of wheat, probably descended from a Korean variety, had been developed in Japan. They greatly impressed Horace Capron, the United States’ commissioner of agriculture, who visited Japan in 1873. “No matter how much manure is used . . . on the richest soils and with the heaviest of yields, the wheat stalks never fall down and lodge,” he noted. In the early twentieth century these Japanese dwarf varieties were crossed with varieties from other countries. One of the resulting strains, Norin 10, was a cross between Japanese wheat and two American varieties. It was developed in Japan, at the Norin breeding station, and was transferred to the United States after the Second World War. Norin 10 had unusually short, strong stems (roughly two feet tall, rather than three feet), and responded well to heavy applications of nitrogen fertilizer. But it was susceptible to disease, so agronomists in different countries be
gan to cross it with local varieties in order to combine Norin 10’s dwarf characteristics with the pest resistance of other varieties. This led to new, high-yielding varieties of wheat suitable for use in particular parts of the world. In industrialized countries where use of nitrogen fertilizer was growing quickly, the new varieties descended from Norin 10 made possible an impressive increase in yield. By this time new, high-yielding varieties of maize had also become widespread, so that during the 1950s the U.S. secretary of agriculture complained that the country was accumulating “burdensome surpluses” of grain that were expensive to store.
When it came to the developing world, one man did more than anyone else to promote the spread of the new dwarf varieties: Norman Borlaug, an American agronomist. He went to Mexico in 1944 at the behest of the Rocke feller Foundation, which had established an agricultural research station there to help to improve poor crop yields. The foundation had concluded that boosting yields was the most effective way to provide agricultural and economic assistance, and reduce Mexico’s dependence on grain imports. Borlaug was put in charge of wheat improvement, and his first task was to develop varieties that were resistant to a disease called stem rust, which was a particular problem in Mexico at the time: It reduced Mexico’s wheat harvest by half between 1939 and 1942. Borlaug created hundreds of crossbreeds of local varieties, looking for strains that demonstrated good resistance to stem rust and also provided strong yields. Within a few years he had produced new, resistant breeds with yields 20 to 40 percent higher than the traditional varieties in use in Mexico.
Mexico was an excellent place to carry out such research, Borlaug realized, because one wheat crop could be grown in the highlands in the summer, and another in the lowland desert in the winter. He developed a new system called “shuttle breeding,” in which he carried the most promising results from one end of the country to another. This broke the traditional rule that plants should only be bred in the area in which they would subsequently be planted, but it sped up the breeding process, since Borlaug could produce two generations a year rather than one. His rule-bending also had another, unanticipated benefit: In order to thrive as both summer and winter crops, the resulting varieties could not afford to be fussy about the difference in the number of hours of daylight between the two seasons. This meant their offspring could subsequently be cultivated in a wide range of different climates.
Norman Borlaug.
In 1952 Borlaug heard about the work being done with Norin 10, and the following year he received some seeds from America. He began to cross his new Mexican varieties with Norin 10, and with a new variety that had been created by crossing Norin 10 with an American wheat called Brevor. Within a few years he had developed new wheat strains with insensitivity to day length and good disease resistance that could, with the use of nitrogen fertilizer, produce more than twice the yield of traditional Mexican varieties. Borlaug wanted to make further improvements, but curious farmers visiting his research station were taking samples of his new varieties and planting them, and they were spreading fast. So Borlaug released his new seeds in 1962. The following year, 95 percent of Mexico’s wheat was based on one of Borlaug’s new varieties, and the wheat harvest was six times larger than it had been nineteen years earlier when he had first arrived in the country. Instead of importing 200,000 to 300,000 tons of wheat a year, as it had done in the 1940s, Mexico exported 63,000 tons of wheat in 1963.
Following the success of his new high-yielding dwarf wheat varieties in Mexico, Borlaug suggested that they could also be used to improve yields in other developing countries. In particular, he suggested India and Pakistan, which were suffering from poor harvests and food shortages at the time and had become dependent on foreign food aid. Borlaug’s suggestion was controversial, because it would mean encouraging farmers to grow wheat rather than indigenous crops. Borlaug maintained, however, that since wheat produced higher yields and more calories, his new dwarf wheat varieties presented a better way for South Asian farmers to take advantage of the advent of cheap nitrogen fertilizer than trying to increase yields of indigenous crops. Monkombu Sambasivan Swaminathan, an Indian geneticist who was an adviser to the agriculture minister, invited Borlaug to visit India, and Borlaug arrived in March 1963 and began promoting the use of his Mexican wheat. Some small plots were planted, and they produced impressive results at the following year’s wheat harvest: With irrigation and the application of nitrogen fertilizer, the yields were around five times that of local Indian varieties, which typically produced around one ton per hectare. Swaminathan later recalled that “when small farmers, who with the help of scientists organised the National Demonstration Programme, harvested over five tons of wheat per hectare, its impact on the minds of other farmers was electric. The clamour for seeds began.”
Another impressive harvest in early 1965 prompted the Indian government to order 250 tons of seed from Mexico for further trials. But wider adoption of the new seeds was held back by political and bureaucratic objections. A turning point came when the monsoon, which normally occurs between June and September, failed in 1965. This caused grain yields to fall by nearly one fifth and made India even more dependent on foreign food aid. The government sent officials to Mexico to place an order for eighteen thousand tons of the new wheat seeds—enough to sow around 3 percent of India’s wheat-growing areas. As the ship carrying the seeds departed for Bombay, war broke out between India and Pakistan, diverting attention from the food crisis gripping the region. And by the time the seeds were being unloaded in September, it was apparent that the monsoon had failed for a second year.
The combination of political instability, population growth, and drought in South Asia gave rise to a new outbreak of Malthusianism in the late 1960s. Across the developing world, the population was growing twice as fast as the food supply. Pundits predicted imminent disaster. In their 1967 book Famine—1975!, William and Paul Paddock argued that some countries, including India, Egypt, and Haiti, would simply never be able to feed themselves and should be left to starve. That same year, one fifth of the United States’ wheat harvest was shipped to India as emergency food aid. “The battle to feed all of humanity is over,” declared Paul Ehrlich in his 1968 bestseller, The Population Bomb. He predicted that “in the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now.” He was particularly gloomy about India, declaring that it “couldn’t possibly feed two hundred million more people by 1980.”
As with Thomas Malthus’s predictions nearly two centuries earlier, the technologies that would disprove these gloomy predictions were already quietly spreading. Following the introduction of Borlaug’s high-yield varieties from Mexico, wheat yields in India increased from twelve million tons in 1965 to nearly seventeen million tons in 1968 and twenty million in 1970. The harvest in 1968 was so large that schools had to be closed in some areas so that they could be used for grain storage. India’s grain imports fell almost to zero by 1972, and the country even became an exporter for a while during the 1980s. Further improvements in yields followed in subsequent years as Indian agronomists crossed the Mexican varieties with local strains to improve disease resistance. India’s wheat harvest reached 73.5 million tons in 1999.
Norman Borlaug’s early success with high-yield dwarf varieties of wheat, meanwhile, had inspired researchers to do the same with rice. The International Rice Research Institute (IRRI), based in the Philippines and funded by the Rocke feller and Ford foundations, was established in 1960. Borlaug’s shuttle-breeding approach was adopted to speed up the development of new varieties. As with wheat, researchers took dwarf varieties, many of them developed in Japan, and crossed them with the local varieties planted in other countries. In 1966 researchers at the IRRI created a new variety, called IR8, by crossing a Chinese dwarf variety (itself derived from a Japanese strain) with an Indonesian strain called Peta. At the time, traditional strains of rice produced yields of around one ton per hectare. The new variety produced
five tons without fertilizer, and ten tons when fertilizer was applied. It became known as “miracle rice” and was quickly adopted throughout Asia. IR8 was followed by further dwarf strains that were more disease resistant and matured faster, making it possible to grow two crops a year for the first time in many regions.
In a prescient speech in March 1968, William Gaud of the United States Agency for International Development had highlighted the impact that high-yield varieties of wheat were starting to have in Pakistan, India, and Turkey. “Record yields, harvests of unprecedented size and crops now in the ground demonstrate that throughout much of the developing world—and particularly in Asia—we are on the verge of an agricultural revolution,” he said. “It is not a violent red revolution like that of the Soviets, nor is it a white revolution like that of the Shah of Iran. I call it the green revolution. This new revolution can be as significant and as beneficial to mankind as the Industrial Revolution of a century and a half ago.” The term “green revolution” immediately gained widespread currency, and it has remained in use ever since.
The impact of the green revolution was already apparent by 1970, and in that year Norman Borlaug was awarded the Nobel Peace Prize. “More than any other single person of this age, he has helped to provide bread for a hungry world,” the Nobel Committee declared. He had “turned pessimism into optimism in the dramatic race between population explosion and our production of food.” In his acceptance speech, Borlaug pointed out that the increase in yields was due not simply to the development of dwarf varieties, but to the combination of the new varieties with nitrogen fertilizer. “If the high-yielding dwarf wheat and rice varieties are the catalysts that have ignited the green revolution, then chemical fertilizer is the fuel that has powered its forward thrust,” he said.