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In the following excerpt, Derek and Charles C. Mann dive into the reason photosynthesis is so inefficient, the resulting need for fertilizer, and some of the key figures in the early production of fertilizer.

Derek Thompson: The story I want to tell today is the story of the Green Revolution, how science and technology overcame scarcity to feed the planet. And we're going to spend most of our time on Norman Borlaug, who is one of these figures of history where if you are a typical news consumer, even one who's deeply curious about the 20th century, you probably haven't heard of this guy. But if you have heard of Norman Borlaug, you probably consider him one of the most important figures in human history. But I don't want to talk about Norman Borlaug's biography first. I want you to tell us about another scientific breakthrough in the 20th century that set the stage for the Green Revolution. And this has to do with fertilizer. Charles, how does fertilizer work, and what role does nitrogen play in the process?

Charles C. Mann: OK, you said, right at the beginning when you talked to me, that I could be nerdy because I have to tell you ...

Thompson: Yes, I did.

Mann: ... I'm going to immediately hit people with nerdy stuff. And this is just deep weeds right off the bat. OK?

Thompson: Fabulous.

Mann: OK, so, journalists have this expression: MEGO, "My eyes glaze over." This is MEGO like right off the bat. Photosynthesis, which is how plants grow, is the most important chemical reaction in the world. Right? Now, the weird thing about photosynthesis is that it's also probably the shittiest chemical reaction in the world in that it's just incredibly inefficient. It's staggeringly inefficient. It's like point and then there's a whole bunch of zeros and then 43 percent efficient. And that's because of a whole bunch of reasons, but the most important is that it originated in this completely bizarre way, which is that a couple billion years ago, some microorganism incorporated another microorganism, and it stays in there. And the functions of these two microorganisms together, they sort of barely stay together, and it allows these plant cells to capture carbon dioxide from the air and water vapor from the air, break up the water, break up the carbon dioxide, and produce the ... carbohydrates that make up plants: the sugars and so forth.

There is a catalyst for this that's called RuBisCO. Now, RuBisCO is also a terrible catalyst. A catalyst is something that facilitates a chemical process but isn't changed itself. It's like an Army recruiter who brings in the recruits, gets them ready, sends them off to the Army, brings in the next recruits, but isn't changed itself. So it's a chemical entity that does this. There are tons of them in your body that are catalyzing reactions, and they typically do thousands of reactions a second. ... RuBisCO may be the worst catalyst on record. So the way that plants overcome this unbelievably inefficient Rube Goldberg system is by just making boatloads of RuBisCO. So some plants, their leaves are like 40 percent RuBisCO. Now, the reason for going through all this is that RuBisCO is basically made out of nitrogen. So plants need nitrogen to make RuBisCO to overcome the terribleness of photosynthesis and grow.

Now, you would think this is not a problem, right? Because 70 percent of the atmosphere is nitrogen. But in this weird bit of bad luck, the nitrogen in the air is two nitrogen molecules stuck together so durably that plants simply don't have the energy to break them apart. The nitrogen has to be in other forms, which is called "bioavailable." I mean, there's all this terrible jargon. I'm just going to dip in, and we'll use a little bit of it, but this one, I think, isn't too bad. So it has to be bioavailable nitrogen. And that's what essentially fertilizer is, is bioavailable nitrogen. And most of the soil in the world doesn't have enough bioavailable nitrogen in it to let plants reach their potential.

Now, in the 1840s, this is all realized by a guy named Justus von Liebig, this great chemist, and he said, "Aha! We need to make fertilizer, and we'll unlock the potential of plant growth." Then they ran into a problem. Nitrogen is really hard to separate.

Thompson: I want to punch down on two points here before we continue the story because this is fabulous. Plants need nitrogen to grow. The air has a lot of nitrogen gas, N2, which is difficult to convert into useful nitrogen, and that's why plants rely on microorganisms in the soil to break down nitrogen into useful forms. This is sometimes called fixing nitrogen, right? The nitrogen gas is converted into something like ammonia, and the plants can use that for photosynthesis. The question facing scientists that we're teeing up here is: "Can we find a way to fix nitrogen more efficiently? Can we find a way to essentially turn this ancient process of converting gaseous nitrogen into useful ammonia? Can we improve on the process that nature took billions of years to develop by bringing it inside of the lab?" What happens next?

Mann: So it took decades and decades, but these two guys, these two German guys, Haber and Bosch, in the first World War, right at the end of the first World War, ... figured out how to make ammonia cheaply and relatively simply in big factories. And that could be broken apart and made into fertilizer. The kind of liquid fertilizer that, if you ever drive through rural areas now, you sometimes smell.

So Fritz Haber was a chemist, and you can think of him as one of these great turn-of-the-century figures like Thomas Edison or Nikola Tesla, these guys who are sort of genius tinkerers. And what he was trying to do is figure out how to break up these nitrogen molecules. And he essentially did what Thomas Edison did for the light bulb. He tried a zillion different ways to do it, and he eventually came up with a catalyst that, because of these chemical complexities that he certainly did not understand at the time, temporarily makes it easier in certain conditions to break up the nitrogen.