Haber & Bosch: Heroes or Not?

The Haber-Bosch process is perhaps one of the most widely known industrial chemical processes. I won’t describe the history in too much detail (there’s Wikipedia for that), but in a nutshell, it’s a chemical process for making ammonia (NH3) from nitrogen (N2) and hydrogen (H2) invented in 1909.

N2 + 3H2 → 2NH3

This doesn’t happen easily, and requires the presence of a friendly helper (metal catalyst), high pressure, and high temperatures. The impact of this discovery was enormous. Ammonia is used as crop fertilizer, and is naturally available in limited amounts (bat poop). However, the H2 in the H-B process can be gotten by steam-reforming the methane (CH4) that makes up 95% of natural gas.

CH4 + 2H2O → CO2 + 4H2

The nitrogen comes free from air. Thus, the H-B process allowed us to use fossil fuels to dramatically increase our supply of nitrogen fertilizer and therefore food.

Haber and Bosch were hailed as heroes of science and engineering1. In 1918, Fritz Haber received the Nobel Prize in Chemistry.

it was clear that the demand for fixed nitrogen…must increase to millions of tons

Fritz Haber in his Nobel Prize speech

Without ammonia, there would be no inorganic fertilizers, and nearly half the world would go hungry”

Vaclav Smil, Detonator of the population explosion2

Phrasings like Smil’s are common. They can lead to confusion between two scenarios: if H-B had never been invented, or if H-B was zapped out of existence today. These scenarios have distinctly different hypothetical consequences. It’s an erroneous conflation to say that without the invention of the H-B process, 4 billion people (half the current population) would have starved. They wouldn’t have, because there were under 2 billion people in total at the beginning of the 20th century.

The H-B process would be a perfectly fine invention if we had infinite fossil fuels and the process was emission and pollution-free. But alas, fossil fuels are a finite resource, and the steam-reforming produces CO2. So as we look towards a future where human population will have to stop growing (or even shrink) due to the depletion of natural resources (reaching carrying capacity), we might wonder how the H-B process changed our population trajectory, and the consequences of that.

Here’s a classic chicken-or-egg question: Would the population have increased despite insufficient food supply, or did the population increase because the food supply did?

Estimate that about half of the population now survives on synthetic fertilizer

I certainly think one answer is far more intuitive, which makes me doubt whether H-B has had a net good impact on humanity. Are Haber and Bosch really agricultural heroes, or did their discovery accelerate the unsustainable growth of the human population, leading to possible greater catastrophe as the population that has since over quadrupled starts running out of fossil fuels and faces climate emergency? In other words, even if mass starvation had been averted in the early 20th century, was it at the cost of an even larger mass starvation in the future?

Technological innovations in this vein are often termed to “save people.”

But if increasing food supply in fact stimulates population growth, (which I think we can safely intuit is a possible effect) then this “saving people” motivator must be questioned. Even if the above plot is an overestimate of lives added by the H-B process, I think it’s safe to assume the H-B process did not merely save people from an early death, but caused the addition of more people that otherwise would never have been created. Is that also “saving”? Can you save someone from non-existence? I think not. Depending on how sunny your view of the long-term future is, the amount of suffering brought about and upon this burst of population could very well exceed the amount averted in early 20th century.

Ethical weighing aside, it’s imperative to recognize that the ballooning population of the past century is undeniably coupled to the extreme and longterm damage wrought on our habitat, and thus our own future.

Of all the century’s technological marvels, the Haber-Bosch process has made the most difference to our survival.

Vaclav Smil2

In light of these thoughts, Smil’s above statement seems unintentionally funny in that it doesn’t specify whether the “difference” is good or bad.

There’s much more to be said about the consequences about the Haber-Bosch process other than population growth. The carbon emissions of steam-reforming. How most of manmade ammonia fertilizer, unlike complex nitrogen sources like compost, gets washed out of fields and wreaks havoc on the ecosystem. All these issues are necessarily large because the scale at which we perform the H-B process.

I think it’s important to think about the implications of technology, rather than treating technological progress as some sort of compulsory joyride. It seems critical for our decision-making ability to improve commensurate with our world-altering ability. So far, it hasn’t. Whether the invention and proliferation of the H-B process is a success story or not is still up for debate.

Updated 10/30/21

  1. Not Haber so much, since he followed this up by pioneering chemical weapons in WWI
  2. Vaclav Smil, Detonator of the population explosion (1999)

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