Have you ever wondered about the process by which scientists pressurize natural gas to turn hydrogen into liquid nitrogen, thereby helping manufacture artificial fertilizer? Don’t worry; no one has. And that’s what “The Alchemy of Air” by Thomas Hager is all about — nitrogen fixation (aka the Haber-Bosch process). But here’s the thing: it’s fascinating. Even more than that: it’s really important.

A little more than 100 years ago, experts believed that the world couldn’t possibly support more than 4 billion people. Even the most efficient farming in the world couldn’t feed more people than that, the thinking went. But now we have a world of 7 billion people. Something must have happened in the meantime. It did, and it was called the Haber-Bosch process. Fritz Haber and Carl Bosch, two remarkable and flawed men, created a way of extracting nitrogen from the air, and using it to make a stunningly good fertilizer. Or, to quote Hager, “They discovered a way to make bread out of air.”

As Hager provocatively states, he believes that this is the most important scientific discovery ever made. Bar none. It’s an exciting statement, and one I’m still not sure I agree with, though it has won me over to some extent. Without the Haber-Bosch process, literally billions of people would have starved to death beginning decades ago.

At the same time, without Haber and Bosch, World Wars I and II may have ended years earlier. Fewer Jews may have died in the gas chambers. Fewer soldiers may have died in the trenches. Fewer explosives would have been made, and fewer gallons of synthetic gasoline would have been produced. Is the world really better for Haber and Bosch?

Haber and Bosch, whose combined legacies imply a close partnership, were hardly even friends. They were temperamental opposites — Bosch adored his wife; Haber alienated his to the point that she killed herself. They barely even knew each other when Haber sold his process to Bosch’s company, and Bosch began trying to apply it on a macro-scale.

Fritz Haber was a German Jew, and despite his conversion to Christianity and decades of uber-patriotic devotion to the motherland, he never lost the stigma of his lineage. Haber was the brash young chemist who figured out how to fix nitrogen from the air. Haber sacrificed his marriage and many of his personal relationships to perfect his technology, and in the end, he triumphed. Yet later in life, Haber served his country by creating the poisonous chlorine gas used in World War I. This discovery also led directly to the development of the gas used in Nazi concentration camps — which ironically almost housed Haber. When Hitler came to power, Haber was forced to flee to Switzerland. He died a year later, a broken man.

Bosch was the more outgoing of the two, and as a young industrialist he figured out how to make Haber’s system practical. Because of Bosch, Haber’s process was used to make enough artificial fertilizer to make the modern world sustainable. But Bosch’s massive factories churned out enough nitrogen to be used as explosives that World War I lasted a year or two longer than it would have otherwise. And Bosch’s other great discovery, how to synthesize gasoline from coal, likely prolonged World War II an additional couple years. Bosch too died in ignominy; after refusing to go along with Hitler’s anti-Semitic regime, he was forced to resign his post.

Haber and Bosch are studies in contrasts. Brilliant men with ruined personal lives. Outgoing leaders wracked with sadness and guilt. They created processes that modernized war, but also made it far more costly. They found a way to feed billions, but their process has polluted our rivers and poisoned our oceans. They rose to the peak of scientific greatness, but died alone and unloved.

They are not, however, forgotten. Hager has captured Haber and Bosch with all the detail of a biographer and all the complex feelings of someone supporting Anthony Weiner for mayor. Hager is an excellent writer whose narrative sometimes borders on the sensationalist, though you can hardly blame him. “The Alchemy of Air” is one of the rare books that has thrilling narrative (complete with great battle scenes and heart-wrenching deaths) and a thought-provoking story. How different would the world have been but for these two men — whom you’d probably never heard of.