We find ourselves in a situation where chemistry is intruding on current events, and I’m referring to something that not everyone seems to have thought about: fertilizer, and especially nitrogen fertilizer. What it is, how it’s used, and especially where it comes from.
Intro to Fertilizer
Now that's a grabber of a subhead, right? But if you’ve bought a bag of the stuff for your garden or your houseplants, you’ve seen the three numbers used to show the strength and balance of any given fertilizer: the first number of that “NPK” rating is nitrogen (elemental nitrogen percentage by weight), the second is phosphorus (phosphate, as percentage by weight of phosphorus pentoxide as a reference compound), and the third is for potassium (percentage by weight of potassium oxide, again as a reference standard).
They’re all important, along with other components like calcium, magnesium, sulfur, and some metal micronutrients as well. The discovery that adding things to the soil could improve production goes back to prehistory, and the ancient uses of animal (or indeed human) manures, dead fish, blood meal and the like are all attempts to increase the available nitrogen. (Phosphate is a story of its own, and a wild one - we’ll do that another day). The problem is of course that the carbon (and carbohydrate) content of a harvested crop comes from the carbon dioxide in the air and water from the ground, both of which one hopes will be back for use next growing season. But nitrogen, phosphorus, and other nutrients can and will be depleted as you harvest the crops and haul them off each year. This loss is much faster than weathering, decay and other such processes that might replenish them in the soil, so adding them back is either crucial right now or will become so in the rather near future no matter where you’re farming. And adding still more (up to a point!) will almost always increase your crop yields, which has been a key concern ever since humans have been burying seeds in the dirt.
Nitrogen in Particular
We are living in a vast sea of nitrogen gas, but it’s so unreactive that it’s useless for biological pathways as it is. You have to somehow reduce to more useful chemical forms like amines, nitrates, and so on. That’s a reaction that soil bacteria had beaten us to by a couple of billion years (the “nitrogen-fixing” ones in the root nodules of legume plants), but doing it on an industrial scale was something else again. By the early 1900s there were a couple of industrial routes to do this: the Birkeland-Eyde process that used electrical discharge arcs and especially the Frank-Caro cyanamide process that used calcium carbide.
Anyone familiar with the history of chemistry (or the history of agriculture) will recognize that human society took a significant turn in the early 20th century with the rise of the Haber-Bosch process. This uses metal catalysts at high temperature and pressure to reduce the nitrogen in the air straight down to ammonia in the presence of hydrogen gas. (Thermodynamic side note: the reaction is enthalpically favorable if you add up heats of formation alone, but the entropy term in the free energy equation kills you because you’re taking four equivalents of gas and turning into just two - thus the need for high temperatures and pressure!) The ammonia is largely turned into urea, which makes a very useful solid fertilizer as is, while some of is diverted into nitric acid/nitrate production, with those latter salts being good fertilizers themselves. Some fertilizer applications (corn especially) just use straight ammonia injected into the soil, poisonous though it is (by the way, in the NPK numbering system ammonia gas is an impressive 82-0-0).
This chemistry quickly spread through the industrialized world, and Haber chemistry continues to reign supreme. And I do mean supreme. Here comes an extremely important point: somewhere around half the world’s population stays alive because of these industrially-produced fertilizers. So it would behoove one to know where they come from. And here’s where the details of the chemistry as well logistics and economics in general need to be considered.
The current situation
I slid past it up there, but you may have noticed that hydrogen is needed for this process - ammonia is just hydrogenated nitrogen gas. So where do you get that? By far the major source for hydrogen has been (and remains) “steam reforming” of methane natural gas, which is another catalytic process (using nickel compounds this time). That’s also done at high temperature and pressure, but you have to be sure to remove all traces of sulfur compounds from the methane, because that will absolutely and irreversibly foul those nickel catalysts. You guessed it - that step takes energy too. Chemically, some of that hydrogen production is sent back around for a “hydrodesulfurization” step, yet another high-pressure high-temperature catalytic step (generally a molybdenum-based mixture) that turns the sulfur compounds in the natural gas into hydrogen sulfide, which is then processed into either elemental sulfur or sulfuric acid. This process is done at virtually all petroleum refineries to strip out sulfur for all sorts of later steps, and that produces huge piles of yellow sulfur that can be easily seen from orbit, far more than the world has a present use for. Back in the days before the oil economy people used to mine sulfur, but you can forget about having to do that now in most of the world.
So as you count it up, nearly every single step of Haber-Bosch ammonia production needs heat and pressure, making the whole route rather energy-intensive (although it’s still a much better deal than the two earlier routes mentioned above, which is a big reason why it replaced them). And boy, do we ever need nitrogen fertilizer (see the previous section), so that price is paid without blinking. Nitrogen is everywhere, but the siting of big Haber-Bosch installations is far more feasible if you have some place with lots of relatively cheap natural gas (as a fuel for all the heating and as a hydrogen source). The biggest one in the world is in Louisiana, and there are others in Texas and Oklahoma. But even so we still import very significant amounts of urea, and that importation is highest at this exact season.
The world nitrogen fertilizer market has really been shaken up by the situation that we have now caused in the Persian Gulf. And after those last couple of paragraphs it’s easy to see why. The Gulf has extraordinary amounts of natural gas, and thus countries in that region have taken advantage of that value-added business opportunity and have become major fertilizer exporters. But not at the moment. Not right when it’s needed in the Northern Hemisphere. All that stuff comes out on huge container ships, down the Gulf and right out the Strait of Hormuz, just like the oil and the liquified natural gas. Prices for all the nitrogen fertilizers were already running high by historic standards before all of this, but now, well. Farm organizations here in the US are calling for financial help from the administration, but after all the tariff nonsense you have to wonder what they’re expecting. Given the reports of mine-laying in the Strait, we might be looking at significant disruptions for some time.
I will resist the impulse to rant and rage. But the likely economic and trade consequences for an Iran war should have been apparent to any reasonably well-informed high school student, much less to the planners at the highest levels of the US government. Indeed, I have no doubt that there are surely competent people left in the various cabinet departments who tried to make this case because they felt as if they could do nothing less. But so much for that. Our leaders have opted instead for the feckless, irresponsible, poorly thought-out mess that we see every morning when we check the news.
It seems a safe bet that the likes of Pete Hegseth and Donald Trump have never thought about industrial nitrogen fixation in their lives. You’ve probably seen the Trotsky quote about “You may not be interested in war, but war is interested in you”. Well, our current leaders are very, very interested in war, so we have that covered, damn it all. But some of the things they’re not interested in are coming back around to bite us.