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We continue the story of nitrogen-fixation with a problematic hero, a scientist whose place in history remains unsettled. Reviled as often as applauded, the German physical chemist, Fritz Haber (Dec. 9, 1868 – Jan. 29, 1934) changed the course of human history.

To his discredit, Haber is justifiably regarded as the father of chemical warfare. Haber’s career coincided with the rise of German militarism, first under Kaiser Wilhelm and then during the early years of the Social Democrats. Haber militarized the chlorine gas used in the First World War. He even served on the ground as an adviser in the use of that chlorine gas at the infamous 2nd Battle of Ypres in Belgium. His institute also developed Zyklon 2 gas, first used as an insecticide but later in the gas chambers of the Nazi death camps. Haber once said, “During peace time a scientist belongs to the world, but during war time he belongs to his country.”

Although Haber had converted to Christianity, he was Jewish. As anti-Semitism spread throughout Germany, Haber was ordered to fire all Jews from the Institute. 75% of his employees were Jewish. He probably could have saved his own job, but he resigned in protest. Invited to Cambridge, his checkered war record followed him. At Cambridge, no less a scientist than Ernest Rutherford, indignant over Haber’s involvement in chemical warfare, pointedly refused to shake his hand.

Haunted by the suicide of his wife and rejection by fellow scientists, Haber was broken. Cambridge became stifling. After several months, Haber accepted an offer from Chaim Weizmann to direct the Sieff Institute in Mandatory Palestine (Now Israel). Already suffering from heart trouble, Haber died on the way in Basil, Switzerland.

Setting aside whatever features of Mr. Hyde there were in Haber, our real interest lies in his Dr. Jekyll who used science to alleviate the perennial threat of starvation. Haber took up the challenge of nitrogen-fixation. This required getting around nitrogen’s strong trivalent bonds. The element’s atoms clung together fiercely. Many scientists had attempted to fix nitrogen but had failed. In 1909 Haber broke the stalemate. He developed a method for producing ammonia from hydrogen gas and atmospheric nitrogen. Using controlled temperature and high pressure, the two gases were passed over a catalyst. In the process, ammonia was produced. This was a game changer. Later, the German chemical engineer, Carl Bosch, modified the process and scaled it up to the industrial level. For his work, Bosch shared the 1931 Nobel Prize in chemistry. Since that time, the industrial production of nitrates has been referred to as the Haber-Bosch process.

For his breakthrough, Fritz Haber was awarded the 1918 Nobel Prize in Chemistry. In his acceptance speech Haber reviewed the challenge that science faced with nitrogen fixation. He emphasized that major sources of remaining nitrates would be depleted by the middle of the 20th century. Haber accurately reminded his audience that without additional nitrates mankind would face large-scale starvation.

It is almost impossible to measure the full impact of Haber’s contributions to science and of the Haber-Bosch process. 100 million tons of synthetic fertilizer are created each year by this method. Scientists estimate that nearly half of the human population today of 7 billion people is fed by the Haber-Bosch process. Some historians have argued that this is perhaps the greatest scientific discovery in history. They argue that the human population today would be unimaginable were it not for the Haber-Bosch process.

However, Haber-Bosch has not been an unalloyed blessing for our planet or for mankind. When World War 1 broke out, Germany had stockpiled only a few months’ worth of nitrates and was essentially cut off from fresh supplies from Chile by the British navy. Since nitrates are required to manufacture all conventional chemical explosives, if Bosch hadn’t succeeded in constructing the first industrial plant for synthetic nitrates in 1913, the war might have ended after a few months instead of lasting four years and costing millions of lives.

In nature there is a nitrogen cycle in which micro-organisms break down nitrogen gas and create usable compounds and finally other micro-organism break down the compounds and release nitrogen gas back into the atmosphere. These are equally balanced processes. Anytime we interfere with a natural cycle, there may be unintended consequences. Some of those consequences may have dire implications. Much of the pollution of global waterways today and most of the eutrophication of fresh water lakes and rivers are the direct consequences of overuse of synthetic nitrogen fertilizers.

Even more disturbing is the fact that the unprecedented growth of our species has been at the expense of countless other species. We have profoundly weakened the complex ecosystem that existed for millions of years before the human population explosion. This has created vulnerabilities we are just beginning to understand.

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