Sign up for our newsletter!

Subscribe form (en)

No spam. Simply good reading. Get your free subscription to Smoltek Newsletter infrequently delivered straight to your inbox.

Your data will be handled in compliance with our privacy policy.

Japanese Bathhouse

Hydrogen feeds the world

Fertilizer production requires large amounts of hydrogen. Today, 95 percent of this hydrogen is produced from fossil fuels, leading to colossal greenhouse gas emissions of CO₂. To save the Earth from more than 2 °C of global warming, politicians are using economic incentives to get the fertilizer industry to switch from fossil hydrogen to clean hydrogen produced by electrolyzers. This makes the fertilizer industry one of the largest markets for electrolyzers. In this blog post, we take a closer look at this little-known market, which, given its size, is more interesting than many of the more well-known ones.

Which mod­ern inven­tion has meant the most to human­ity? The steam engine, train, air­plane, car, space rock­et, nuc­le­ar power, radio, tele­vi­sion, com­puter, AI, …? The list of con­tenders is long. But none of them can match…

Sound a fan­fare, please!

…the Haber-Bosch process.

Haber & Bosch

Haber and Bosch!? What have Peter Haber and Harry Bosch done for human­ity? you ask in disbelief.

Well, they have enter­tained us. At least a few of us. Peter Haber is a Swedish act­or best known for play­ing Mar­tin Beck, and Harry Bosch is a fic­tion­al char­ac­ter in Michael Connelly’s nov­els. But they are, of course, not the Haber and Bosch behind the mod­ern inven­tion that has meant the most to humanity.

The Haber and Bosch I am talk­ing about are the Ger­man chem­ists Fritz Haber and Carl Bosch. They developed a chem­ic­al pro­cess in the early 20th cen­tury that now car­ries their name. This pro­cess has been jus­ti­fi­ably described as “the most import­ant inven­tion of the twen­ti­eth century.”

But before we dig into what the pro­cess does and why it deserves the first spot above all oth­er con­tenders, we need to take a deep breath and get some context.


The breath we just took con­tained 78 per­cent nitro­gen gas (N2). 78.1 per­cent, to be exact. That makes nitro­gen (N), by far, the most com­mon ele­ment in the air we breathe. It is also one of the most com­mon  ele­ments in the whole universe.

Nitro­gen is also one of the build­ing blocks of life. Lit­er­ally. It’s in amino acids, pro­teins, DNA, RNA and ATP. (The lat­ter is the fuel that our cells run on.)

But it’s not by breath­ing air that your body gets the nitro­gen it needs.

The nutrient source of nitrogen

You get nitro­gen by eat­ing plants, or by eat­ing anim­als that have pre­vi­ously eaten plants, or by eat­ing anim­als that have pre­vi­ously eaten oth­er anim­als that have pre­vi­ously eaten…

Ok, you get the pic­ture. The food chain. The point is that plants are ulti­mately our source of nitro­gen intake.

But how does the nitro­gen get into the plants?

Simple: their roots absorb it from the soil they grow in.

But how does the nitro­gen end up in the soil? you ask relentlessly.

Today, the primary source is nitro­gen fer­til­izer that farm­ers spread on fields. But let’s hold off on that. We start by look­ing at how nature does it without the help of humans.

Nitrogen fixation

Enter the scene: Diazotrophs.


Diazo­trophs is a col­lect­ive name for bac­teria and oth­er microor­gan­isms that con­vert nitro­gen in the air into nitro­gen com­pounds, mainly ammo­nia (NH3), which plants can take up. This pro­cess is called nitro­gen fix­a­tion.

Nitrogen’s circle of life

When plants die, bac­teria and fungi sink their teeth into the remains. (Fig­ur­at­ively speak­ing, of course; bac­teria and fungi have no teeth.) The same thing even­tu­ally hap­pens to anim­als and humans as well. Their remains con­tain nitro­gen com­pounds (pro­teins, DNA, RNA, and so on). Some microbes can break these down, releas­ing nitro­gen into the atmo­sphere. This pro­cess is called deni­tri­fic­a­tion.Nitro­gen fix­a­tion and deni­tri­fic­a­tion are thus part of the great circle of life, which Mufasa teaches young Simba in the movie The Lion King. This cycle is known in sci­ence as the nitro­gen cycle.

Listen to the song Circle Of Life from the movie The Lion King.

Need for fertilizers

Does the nitro­gen cycle go by itself?

If nature is left to take care of itself, the nitro­gen cycle ticks along without any prob­lems. But as soon as human­ity put the plow in the ground and star­ted farm­ing, the bal­ance was disturbed.

If crops are grown in the same place over a few years, the plants take up more nitro­gen from the soil than nat­ur­al pro­cesses can restore. This is why humans have come up with strategies such as slash-and-burn agri­cul­ture, crop rota­tion, and fertilization.

The prac­tice of fer­til­iz­a­tion dates back to ancient times, with early civil­iz­a­tions such as the Sumeri­ans and Egyp­tians using manure to enrich soil around 2000 BCE. This early form of fer­til­iz­a­tion helped improve crop yields, show­cas­ing human­ity’s ini­tial under­stand­ing of enhan­cing soil fer­til­ity for agri­cul­tur­al purposes.

Father of the fertilizer industry

Manure and humus have been used as fer­til­izers since the time of the Sumeri­ans and the Egyp­tians. How­ever, the idea of cre­at­ing a syn­thet­ic fer­til­izer was not born until the 19th century.

In his ground­break­ing book Die organ­is­che Chemie in ihr­er Anwendung auf Agri­cul­tur und Physiolo­gie, first pub­lished in 1840, the Ger­man chem­ist Jus­tus von Liebig argued that nitro­gen com­pounds, such as ammo­nia, were needed to grow the health­i­est crops pos­sible. This earned him the epi­thet “fath­er of the fer­til­izer industry.”

Jus­tus von Liebig’s the­ory led to a rush for nitro­gen at the end of the 19th cen­tury. Salt­peter was mined with an unpre­ced­en­ted frenzy, and trop­ic­al rocks were scraped for guano.

Watch the video to learn about how the demand for guano led the U.S. to pass a law giv­ing Amer­ic­an cit­izens exclus­ive rights to guano on unclaimed islands.

Sources of nitrogen fertilizers

But salt­peter mines and bird poop only went so far.

At the end of the 19th cen­tury, it was real­ized that nat­ur­al sources were not suf­fi­cient to meet future needs. This sparked the idea of some­how extract­ing nitro­gen dir­ectly from thin air.

Sev­er­al meth­ods were developed to fix the nitro­gen in the air. But it was not until the begin­ning of the next cen­tury that the real break­through came, albeit with a humble beginning.

Ammonia from thin air

In 1905, Fritz Haber pro­duced a small amount of ammo­nia by mix­ing nitro­gen and hydro­gen at 1,000 °C in the pres­ence of an iron cata­lyst. How­ever, the high tem­per­at­ure made the meth­od impractical.

Over the next few years, Fritz Haber refined his tech­nique. In March 1909, he presen­ted a meth­od in which the tem­per­at­ure had been reduced to the more man­age­able range of 500–600 °C. This was accom­plished with high pres­sure. The pro­cess requires almost 200 times the air pres­sure (20 MPa).

But there was a caveat. The ammo­nia was pro­duced drop by drop; it took 8 hours to pro­duce a single liter of ammo­nia. Nev­er­the­less, Fritz Haber had demon­strated a viable solu­tion for extract­ing nitro­gen from the air and fix­ing it as ammonia.

Watch the video for more inform­a­tion on Fritz Haber.

Haber-Bosch process

The Ger­man chem­ic­al com­pany BASF pur­chased the rights to the pro­cess and tasked Carl Bosch with scal­ing up Haber’s tab­letop machine to indus­tri­al scale. Four years later, the BASF fact­ory in Oppau pro­duced five tons of ammo­nia – per day.

This is why the pro­cess is named after the two men: The Haber-Bosch pro­cess.

Haber and Bosch were awar­ded the Nobel Prize in 1918 and 1931, respect­ively, for their work in solv­ing the chem­ic­al and engin­eer­ing prob­lems of large-scale, con­tinu­ous flow and high-pres­sure technology.

Fritz Haber Carl Bosch
Fritz Haber and Carl Bosch.

Telling correlation

Ini­tially, Haber-Bosch pro­cess was mainly used to pro­duce ammo­nia for the mil­it­ary and industry, but after the Second World War, the use of ammo­nia as a nitro­gen fer­til­izer in agri­cul­ture exploded.

The increased use of syn­thet­ic nitro­gen fer­til­izer led to high­er yields that sup­por­ted a rap­idly grow­ing pop­u­la­tion. That’s why Pro­fess­or Vaclav Smil wrote in the pres­ti­gi­ous sci­entif­ic journ­al Nature that the Haber-Bosch pro­cess ”is the most import­ant inven­tion of the twen­ti­eth century.”

Global World Population And Fertiliser Use
Source: N. Alex­an­dratos and J. Bru­insma, World Agri­cul­ture Towards 20302050: The 2012 Revi­sion, Food and Agri­cul­ture Organ­iz­a­tion of the United Nations, ESA Work­ing Paper No. 12–03, June 2012.

High cost for feeding the world

An often-quoted stat­ist­ic is that nitro­gen fer­til­izers are respons­ible for feed­ing half the world’s population.

Since this fer­til­izer is pro­duced through the Haber-Bosch pro­cess by con­vert­ing hydro­gen, I think it’s fair to say that hydro­gen feeds the world.

Don’t you agree?

But the mass adop­tion of syn­thet­ic fer­til­izers has come at a high cost to the envir­on­ment: harm­ful algal blooms, soil acid­i­fic­a­tion, and massive green­house gas emissions.

Greenhouse effect

A study estim­ates that the pro­duc­tion and use of nitro­gen fer­til­izers, both organ­ic and syn­thet­ic, in food-grow­ing accounts for around 5 per­cent of glob­al green­house gas emis­sions and that this could threaten efforts to keep glob­al warm­ing below 2 °C.

Nitro­gen fer­til­izers con­trib­ute to the green­house effect in many ways.

One issue is that far from all fer­til­izer is absorbed by plants, and what remains is broken down by microbes in the soil, pro­du­cing laugh­ing gas (N2O).

That’s not funny at all. (Pun inten­ded, of course.)

Laugh­ing gas, or nitrous oxide, which is its chem­ic­al name, is a green­house gas almost 300 times more potent than car­bon diox­ide (CO2).

But anoth­er major source is the pro­duc­tion itself. The man­u­fac­ture of arti­fi­cial fer­til­izers is respons­ible for almost 1.5 per­cent of total glob­al CO2 emissions.

Energy-hungry monster

The Haber-Bosch pro­cess is car­ried out at high tem­per­at­ures and pres­sure, turn­ing the pro­duc­tion plants into energy-hungry mon­sters. The energy comes from burn­ing nat­ur­al gas.

Nat­ur­al gas is also used to pro­duce gray hydro­gen, which is the feed­stock in the Haber-Bosch pro­cess. Much hydro­gen is needed. Remem­ber that form­ing ammo­nia takes three hydro­gen atoms per nitro­gen atom (NH3).

About 40 per­cent of the fossil gas input into the pro­cess is burned to fuel the reac­tion, with the remain­ing 60 per­cent being used as feedstock.

Pro­du­cing ammo­nia fer­til­izers is respons­ible for about 1 per­cent of all glob­al energy use and 1.4 per­cent of CO2 emissions.

Carbon dioxide polluter

More than 180 mil­lion met­ric tons of ammo­nia are pro­duced annu­ally. Nearly 90 per­cent of ammo­nia is used to pro­duce syn­thet­ic nitro­gen fer­til­izers (includ­ing urea, ammoni­um nitrate, and ammoni­um phosphate).

Pro­du­cing this massive amount of ammo­nia requires more than 32 mil­lion met­ric tons of hydro­gen. Today, more than 95 per­cent of this hydro­gen is pro­duced from nat­ur­al gas and coal.

To pro­duce 32 mil­lion tons of hydro­gen by steam meth­ane reform­ing (SMR), the most com­mon meth­od, approx­im­ately 80 mil­lion tons of nat­ur­al gas are required, assum­ing an effi­ciency rate of 80 per­cent for the SMR process.

Thus, we can cal­cu­late that 68 mil­lion tons of nat­ur­al gas are needed just as a feed­stock in the pro­duc­tion of nitrite fer­til­izer. The Haber-Bosch pro­cess con­sumes an addi­tion­al 45 mil­lion tons of nat­ur­al gas as fuel. In total, 113 mil­lion tons of nat­ur­al gas are needed annu­ally to pro­duce syn­thet­ic nitro­gen fertilizers.

When all this nat­ur­al gas is used, more than a stag­ger­ing 310 mil­lion met­ric tons of car­bon diox­ide (CO2) are released into the atmosphere.


Need for PEM-electrolyzers

For hydro­gen to con­tin­ue to feed half the world while keep­ing glob­al warm­ing below 2 °C, the pro­duc­tion of syn­thet­ic nitro­gen fer­til­izers must switch from fossil-based hydro­gen to fossil-free hydro­gen rather quickly.

How­ever, this requires many PEM-elec­tro­lyz­ers to pro­duce the fossil-free hydrogen.

Smoltek’s role

Wheth­er an elec­tro­lyz­er pro­duces hydro­gen to feed the world or power a sports car, there is a problem.

The cell mater­i­al in a PEM-elec­tro­lyz­er con­tains iridi­um. Today, 2.0 mil­li­grams of iridi­um are used per square cen­ti­meter. That doesn’t sound like much, but it is a lot, giv­en that iridi­um is a scarce met­al prac­tic­ally only mined in South Africa. (Some are also mined in Canada and Russia.)

The price of iridi­um is sky-high and expec­ted to rise sharply with the increased demand, as it is prac­tic­ally impossible to extract more per year than already done.

This is why all man­u­fac­tur­ers and buy­ers of PEM elec­tro­lyz­ers want to reduce the amount of iridi­um from the cur­rent 2.0 to an ambi­tious 0.1 mil­li­grams per square centimeter.

Research­ers and developers world­wide are work­ing frantic­ally to reach this dream goal. So are we. And I would say that we are ahead of the game thanks to our unfair advant­age.So, if you ever had doubts about the decision to pur­sue the hydro­gen mar­ket in par­al­lel with the semi­con­duct­or mar­ket, it’s time to stop doubt­ing. Don’t you agree?

Sign up for our newsletter!

Subscribe form (en)

No spam. Simply good reading. Get your free subscription to Smoltek Newsletter infrequently delivered straight to your inbox.

Your data will be handled in compliance with our privacy policy.

Latest posts