0:00:07.239,0:00:08.052
What would you say

0:00:08.052,0:00:09.579
is the most important discovery

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made in the past few centuries?

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Is it the computer?

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The car?

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Electricity?

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Or maybe the discovery of the atom?

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I would argue that it is this chemical reaction:

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a nitrogen gas molecule

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plus three hydrogen gas molecules

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gets you two ammonia gas molecules.

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This is the Haber process

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of binding nitrogen molecules in the air

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to hydrogen molecules,

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or turning air into fertilizer.

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Without this reaction,

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farmers would be capable of producing enough food

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for only 4 billion people;

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our current population is just over 7 billion people.

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So, without the Haber process,

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over 3 billion people would be without food.

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You see, nitrogen in the form of nitrate, NO3,

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is an essential nutrient for plants to survive.

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As crops grow, they consume the nitrogen,

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removing it from the soil.

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The nitrogen can be replenished

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through long, natural fertilization processes

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like decaying animals,

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but humans want to grow food

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much faster than that.

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Now, here's the frustrating part:

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78% of the air is composed of nitrogen,

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but crops can't just take nitrogen from the air

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because it contains very strong triple bonds,

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which crops cannot break.

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What Haber did basically

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was figure out a way

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to take this nitrogen in the air

0:01:29.529,0:01:31.281
and put it into the ground.

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In 1908, the German chemist Fritz Haber

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developed a chemical method

0:01:36.176,0:01:39.020
for utilizing the vast supply of nitrogen in the air.

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Haber found a method

0:01:39.890,0:01:41.594
which took the nitrogen in the air

0:01:41.594,0:01:43.046
and bonded it to hydrogen

0:01:43.046,0:01:45.242
to form ammonia.

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Ammonia can then be injected into the soil,

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where it is quickly converted into nitrate.

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But if Haber's process was going to be used

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to feed the world,

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he would need to find a way

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to create a lot of this ammonia quickly and easily.

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In order to understand

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how Haber accomplished this feat,

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we need to know something

0:02:02.179,0:02:04.397
about chemical equilibrium.

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Chemical equilibrium can be achieved

0:02:06.346,0:02:09.514
when you have a reaction in a closed container.

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For example, let's say you put

0:02:11.233,0:02:14.346
hydrogen and nitrogen into a closed container

0:02:14.346,0:02:16.158
and allow them to react.

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In the beginning of the experiment,

0:02:17.757,0:02:20.370
we have a lot of nitrogen and hydrogen,

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so the formation of ammonia

0:02:22.006,0:02:24.098
proceeds at a high speed.

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But as the hydrogen and nitrogen react

0:02:26.680,0:02:28.261
and get used up,

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the reaction slows down

0:02:29.883,0:02:31.842
because there is less nitrogen and hydrogen

0:02:31.842,0:02:33.625
in the container.

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Eventually, the ammonia molecules reach a point

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where they start to decompose

0:02:38.058,0:02:41.339
back into the nitrogen and hydrogen.

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After a while, they two reactions,

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creating and breaking down ammonia,

0:02:45.588,0:02:47.634
will reach the same speed.

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When these speeds are equal,

0:02:49.341,0:02:52.147
we say the reaction has reached equilibrium.

0:02:53.146,0:02:55.280
This might sound good, but it's not

0:02:55.280,0:02:56.511
when what you want

0:02:56.511,0:02:58.817
is to just create a ton of ammonia.

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Haber doesn't want the ammonia

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to break down at all,

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but if you simply leave the reaction

0:03:03.374,0:03:04.865
in a closed container,

0:03:04.865,0:03:06.487
that's what will happen.

0:03:06.487,0:03:08.794
Here's where Henry Le Chatelier,

0:03:08.794,0:03:09.981
a French chemist,

0:03:09.981,0:03:11.271
can help.

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What he found was

0:03:12.705,0:03:14.590
that if you take a system in equilibrium

0:03:14.590,0:03:16.296
and you add something to it,

0:03:16.296,0:03:17.723
like, say, nitrogen,

0:03:17.723,0:03:18.715
the system will work

0:03:18.715,0:03:20.921
to get back to equilibrium again.

0:03:20.921,0:03:22.296
Le Chatelier also found

0:03:22.296,0:03:23.469
that if you increase

0:03:23.469,0:03:25.596
the amount of pressure on a system,

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the system tries to work

0:03:26.761,0:03:28.978
to return to the pressure it had.

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It's like being in a crowded room.

0:03:30.675,0:03:32.182
The more molecules there are,

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the more pressure there is.

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If we look back at our equation,

0:03:35.529,0:03:37.532
we see that on the left-hand side,

0:03:37.532,0:03:39.681
there are four molecules on the left

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and just two on the right.

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So, if we want the room to be less crowded,

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and therefore have less pressure,

0:03:45.872,0:03:46.779
the system will start

0:03:46.779,0:03:48.670
combining nitrogen and hydrogen

0:03:48.670,0:03:51.804
to make the more compact ammonia molecules.

0:03:51.804,0:03:53.821
Haber realized that in order to make

0:03:53.821,0:03:55.100
large amounts of ammonia,

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he would have to create a machine

0:03:56.604,0:03:59.600
that would continually add nitrogen and hygrogen

0:03:59.600,0:04:01.438
while also increasing the pressure

0:04:01.438,0:04:03.314
on the equilibrium system,

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which is exactly what he did.

0:04:05.480,0:04:08.030
Today, ammonia is one of the most produced

0:04:08.030,0:04:10.313
chemical compounds in the world.

0:04:10.313,0:04:14.891
Roughly 131 million metric tons are produced a year,

0:04:14.891,0:04:18.314
which is about 290 billion pounds of ammonia.

0:04:18.314,0:04:19.363
That's about the mass

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of 30 million African elephants,

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weighing roughly 10,000 pounds each.

0:04:24.314,0:04:28.087
80% of this ammonia is used in fertilizer production,

0:04:28.087,0:04:29.041
while the rest is used

0:04:29.041,0:04:30.937
in industrial and household cleaners

0:04:30.937,0:04:33.314
and to produce other nitrogen compounds,

0:04:33.314,0:04:35.265
such as nitric acid.

0:04:35.265,0:04:36.345
Recent studies have found

0:04:36.345,0:04:38.837
that half of the nitrogen from these fertilizers

0:04:38.837,0:04:41.147
is not assimilated by plants.

0:04:41.147,0:04:42.977
Consequently, the nitrogen is found

0:04:42.977,0:04:44.642
as a volatile chemical compound

0:04:44.642,0:04:47.695
in the Earth's water supplies and atmosphere,

0:04:47.695,0:04:49.646
severely damaging our environment.

0:04:49.646,0:04:51.475
Of course, Haber did not foresee this problem

0:04:51.475,0:04:53.095
when he introduced his invention.

0:04:53.095,0:04:54.773
Following his pioneering vision,

0:04:54.773,0:04:56.388
scientists today are looking

0:04:56.388,0:04:59.054
for a new Haber process of the 21st century,

0:04:59.054,0:05:01.029
which will reach the same level of aid

0:05:01.029,0:05:03.359
without the dangerous consequences.