During the last hundred years, the world experienced an explosion in population growth that we seldom seem to acknowledge and appreciate. Faster than at any other time in human history, we almost quadrupled the population in less than a hundred years, from 2 billion in 1930 to 7.8 billion by 2020.
Naturally, with population growth came a similar expansion in food production. Historians debate whether the increase in food production was a happy coincidence during a formidable population expansion era (and one that saved the world from mass starvation) or the main force driving it.
In his book “Sapiens: A Brief History of Humankind,” Yuval Noah Harari reasoned that: “…The Agricultural Revolution certainly enlarged the total sum of food at the disposal of humankind, but the extra food did not translate into a better diet or more leisure. Rather, it translated into population explosions…”.
Though this debate is not the main point of this piece, it’s hard to imagine one without the other. And food production growth during the last century is as impressive as population growth. In the US alone, production of bushels of corn, for example, increased fivefold during the same period, from 3bn in 1930 to 15bn in 2020.
What’s so remarkable about this growth is that the land area allocated to producing that corn stayed relatively the same during the period, while the number of humans working those lands decreased almost four times.
A key element in this yield expansion, also known as the first chemical global revolution, was invented in 1909 by Fritz Haber and Carl Bosch. Through the Haber-Bosch process, as it is known, they developed an artificial nitrogen fixation process that enabled the large-scale production of ammonia by converting atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using a metal catalyst under high temperatures and pressures.
Ammonia, when applied into the ground, releases its nitrogen which is an essential nutrient for fertilizing soils and growing plants, including farm crops and lawns. Most of the ammonia in the environment comes from the natural breakdown of manure, dead plants, and animals. The Haber-Bosch introduced an artificial way to accelerate this natural process and mass-produce it to enrich the same farmable lands that enabled (or caused?) the expansion of our society.
Today, about 90 percent of the 160mm tons of ammonia produced yearly worldwide ends in fertilizers.
Though a revolution in food production yield expansion, this process emits 1.5–1.6 tons of CO2-equivalent per ton of ammonia, accountable for 1.2% of global CO2 emissions. Most of that is a direct result of using methane as feedstock to obtain hydrogen. At the same time, the high pressures and temperatures of steam methane reforming (obtaining hydrogen) also account for over 85% of the energy required during the Haber-Bosch process. This energy intensity puts the methane-fed Haber-Bosch in the top positions of global energy consumption, at 2% of the world’s energy. Obtaining hydrogen, as it’s evident, is hard. But the good news is that almost all the ammonia-related carbon emissions come from its manufacturing, specifically from obtaining hydrogen to combine with nitrogen and none from its application.
Another way to get hydrogen
Hydrogen is abundant. But the problem with obtaining it is that it never comes in a readily usable form. Atomic hydrogen bonds tightly to whatever is around. In water, the bond between hydrogen and oxygen is hard to break. Liberating hydrogen from water can be done by electrolysis, a process that uses electricity to break this bond.
Using renewable energy, such as solar or wind, to power electrolysis and an electrically-driven Haber Bosch process could reduce CO2 emissions by 92%. From being accountable for 1.2% of global CO2 emissions to almost nothing in real terms. It would still be highly energy-intensive and thus viable only in regions with abundant renewable resources that don’t compete with urban areas. The Atacama desert and the Magallanes region in South America are such areas. Producing hydrogen to manufacture CO2-free ammonia in such renewable energy conditions makes its outcome more competitive than current CO2-full ammonia prices.
Ammonia’s second revolution
The most important aspect of this carbon-free compound goes beyond its capabilities as a fertilizer. The fact that ammonia liberates no carbon emissions when applied extends to other uses, such as burning it for power generation. Coal plants, such as the Japanese Jera or Intermountain Power in Utah, are planning a transition with relatively low technological modifications to burning ammonia (or hydrogen directly) to generate power without carbon emissions. Another example is transportation. Hyundai Heavy Industries and Korea Shipbuilding & Offshore Engineering Co. received the first Approval in Principle for an ammonia carrier with ammonia-fueled propulsion, while Maersk is planning for all future new build vessels under its ownership to use carbon-neutral fuels, such as ammonia, to start abating shipping-related emissions, which account for almost 3% of carbon dioxide emissions.
In this sense, if batteries enable energy storage for hours, carbon-free ammonia enables the storage of renewable energy for years. It even allows for transporting renewable energy from where it is abundant to where it is most needed. This opens a whole new world of possibilities for decarbonizing our lives and enabling a new set of energy-powered applications, starting with cars (which today run on coal or gas power plants for the most part.) Carbon-free ammonia could be on the verge of revolutionizing societies once again.
There’s still a way to go before producing carbon-free ammonia at scale. Most of it still depends on future innovation. Efficiency improvements should come from the electrolysis step for hydrogen production. PEM electrolyzers today have a comparable efficiency of ~60% and could increase to ~75% in the near term. By nature, they need to be agile due to the geographically isolated and intermittent nature of renewable energy. In this sense, replacing methane reforming with electrolysis begins to enable both requirements because electrolysis is inherently modular and can be started/stopped much more quickly than multistage, heat-integrated methane reforming reactors. Further technological progress will not only reduce energy consumption but also installation and operation costs, durability, and safety.
South America is on track to produce the most competitive and reliable carbon-free ammonia supplies. As more industries widen their energy scope, following heavy transportation, power, and fertilizers, the faster it would be for leading nations to achieve CO2 targets in their national strategies.