At a recent EA meetup, someone mentioned fertilizers in the context of climate change and global food production. Admittedly, I had never thought about fertilizers before, except when I’ve been trying to get the tomato plants on my balcony to grow more than five tomatoes per season (I have yet to find my green thumb). Turns out fertilizers are a wildly fascinating topic! I dug into it a bit and decided to write up my findings as I assume others might also learn a lot about fertilizers and how they fit into the bigger picture. 

This post is the product of around twelve hours of research (plus twelve hours of write-up). It is by no means comprehensive and I wonder if I’ve come to the right conclusions in some sections. Any feedback is highly welcome, as well as corrections and resources that could fill in gaps or contradict anything I’ve written here.

Summary

• Fertilizers provide what plants need to grow: nitrogen, potassium and phosphorus (in addition to sunlight and water).
• Humans have used organic fertilizers for thousands of years and started using synthetic fertilizers in the 20th century.
• While phosphate and potassium fertilizer is made from mined phosphorus and potash, respectively, nitrogen fertilizer is mostly produced through combining hydrogen from natural gas with atmospheric nitrogen via the Haber-Bosch process.
• 58% of fertilizers are nitrogen fertilizers, with China, the US, India and Russia being the world’s largest producers. Potash is mainly mined in Canada, Belarus and Russia, phosphorus comes mostly from China.
• Fertilizers have vastly increased food production in the last 100 years and it is estimated that about 50% of today’s global population rely on fertilizers for their food supply, making fertilizers one of the “four pillars of civilization”.
• In comparison to almost all other regions in the world, crop yields in Sub-Saharan Africa are still very low, an unsettling fact given Sub-Saharan Africa’s fast population growth and high rates of undernourishment. This is partly the result of too little fertilizer use.
• Because fertilizer is so good at increasing crop yields, it means we can produce more food on the same or even less farmland, helping to preserve wildlife habitats and biodiversity.
• Many countries around the world use a lot of fertilizers—in fact, many use too much, including China, Mexico, Brazil, Colombia and Thailand, and could maintain their food production even with lower fertilizer use.
• Producing ammonia for nitrogen fertilizers relies heavily on natural gas, consumes around 2% of the global energy supply and constitutes about 5% of global anthropogenic greenhouse gas emissions, so we need to find ways to produce nitrogen fertilizer more sustainably.
• There is a range of ongoing development for producing “green ammonia” but most of them are still in their early stages, and it is unclear whether new production technologies can cover future needs for ammonia.
• Although higher crop yields and fertilizer use seem to be vital for improving food security in Sub-Saharan Africa, the issue is relatively unexplored in EA. It seems worthwhile to have a deeper look into this issue and think about potential cost-effective interventions as well as how they compare to top interventions in global health and development.

What are fertilizers?

Plants need three things to grow: sunlight, water and nutrients. Fertilizers provide plants with the latter, more specifically with phosphorus, potassium and nitrogen [1].

Hang on, but why do we need to give a plant nitrogen? Isn’t our air made up of 78% nitrogen? Yes, but atmospheric nitrogen cannot be used by plants directly and instead needs to be converted into ammonia or other nitrogenous compounds in the soil. This process is called "nitrogen fixation" and is carried out by certain soil microorganisms or takes place during lightning. The only plants that can turn nitrogen from the air into ammonia themselves are legumes, including beans, peas and lentils [36].

How are fertilizers produced? 

Out of all nutrients, plants are usually in shortest supply of nitrogen. For example, one hectare of farmland has on average 10-15 kg of nitrogen available per year (via biological nitrogen fixation through bacteria and lightning) but grain crops need around ten times as much for an optimal harvest [3]. 

So it’s no wonder fertilizers are as old as agriculture itself. Traditionally, they come from organic sources like human/animal manure and plant compost [1]. However, organic fertilizers don’t contain enough nitrogen to cover most plants nitrogen needs due to their relatively low nitrogen content [14]. Nitrogen supply is also limited by the total availability of organic fertilizers. Even during the Industrial Revolution in Europe, when much of the manure of animals and humans from cities was used to fertilize crops, fertilizer demand could still not be met [3, 14]. 

In the 19th century, people started experimenting to make synthetic fertilizers. At the beginning of the 20th century, the Haber-Bosch process was developed, which uses natural gas and atmospheric nitrogen to produce ammonia, the basis for nitrogen fertilizers. Incidentally, ammonia is also used to make explosives, so the industrialized ammonia production after World War II was helped by utilizing obsolete wartime bomb factories. The Haber-Bosch process remains the most common way to produce nitrogen fertilizer until today [1]. Over half of today’s global fertilizer consumption is nitrogen-based [4]. Its production is fairly centralized, with the largest producer being China, followed by the US, India and Russia [27].

So much for nitrogen. What about phosphorus and potassium? Both are sourced from mined materials. Phosphate fertilizers are made from phosphate rock and primarily produced in China and Canada, while potassium fertilizers are made from potash, mainly in Russia and Belarus [1, 4, 6].

Fertilizers are really really awesome

What I was most surprised to learn was how big of a deal fertilizers were and continue to be for humanity.

Fertilizers have vastly increased food production in the last 100 years and it is estimated that we can feed almost twice as many people today as we would be able to without synthetic fertilizers [2]. This is why together with steel, concrete and plastics, ammonia is regarded as one of the “four pillars of civilization”. 

In the last 50 years, the global population has roughly doubled, so it is astounding that we’ve been able to feed everybody. This is largely thanks to the Green Revolution, which started in developed countries after World War II and spread around the world throughout the 20th century. The Green Revolution brought about the large-scale use of technology in agriculture, including high-yielding crop varieties, improved irrigation systems, mechanization, and—you guessed it—increased synthetic fertilizer use [7].

To cite some numbers and make this boost in crop yield more palpable: between 1961 and 2021, the average global cereal yields have risen by 320% (from 1.4 to 4.2 tons per hectare per year) soybean yields by 250% (from 1.1 to 2.9 tons per hectare per year) and potato yields by 170% (from 12.2 to 20.7 tons per hectare per year) [8]. 

I can recommend having a look at Our World in Data’s resources for more examples of how crop yields have risen over the years. Fertilizers are not the only thing responsible for this but they are nevertheless an extremely important contributor. 

The only region that hasn’t profited as much from the Green Revolution is Sub-Saharan Africa, and compared to basically all other regions in the world, crop yields are still meager [11]. For instance, cereal yields are 50% of that of India and 20% of that of the US [12]. One of the main reasons for this is that fertilizer use in Sub-Saharan Africa is lower than in any other region. For example, while China uses around 260 kg per hectare of cropland per year and the US 96 kg, Sub-Saharan African countries only use around 20 kg [26]. 

This is worrying, considering Sub-Saharan Africa is the poorest region in the world, with 40% of people living below the poverty line of 1.90$ per day [13]. The region’s population is expected to grow a lot in the coming decades, an estimated 1.1 billion by 2050. So making their food production more efficient is vital. This means pushing fertilizer use in Sub-Saharan Africa is critical to reach a more self-sufficient food production and to feed its population (currently, the region is a net importer of food) [13, 14].

Since the Industrial Revolution, more efficient food production meant fewer and fewer people had to work in agriculture. While around 1800, 40-60% of the European population worked in agriculture, nowadays only 2-5% does so [9]. Compare this to the 50% of people in Sub-Saharan Africa still working in the agricultural sector. Being an African farmer generally means earning very little, thus having low chances to escape extreme poverty. So allowing more people to leave agriculture and work in a different sector—all enabled through more efficient farming—would help raise their income [13]. 

Another crucial reason for increasing fertilizer use in Sub-Saharan Africa relates to the connection between fertilizers and land use. Because fertilizers are so good at increasing crop yields, it means that while global food production has vastly risen, the area of agricultural land needed has only slightly increased. For example, although global cereal yields have grown by 280% between 1961 and 2014, land used for it has only increased marginally, by 16%. Land use for cereal production has even gone down in Europe and the US [11]. By contrast, because Sub-Saharan Africa hasn’t succeeded in making its food production more efficient, it is using more and more land to grow food—with meager gains [13].

Nowadays, nearly half of all habitable land is used for agriculture [15]. This is bad because farmland expansion is the greatest factor driving habitat loss and with it loss of wildlife and biodiversity. Because of population growth as well as rising demands for meat and dairy, the world is estimated to need around 26% more cropland by 2050 (an area the size of India and Germany combined). Most of this expansion in agricultural land is expected to happen in Sub-Saharan Africa. Consequently, the region is projected to have the greatest loss in natural habitat (over 12% compared to the global average of around 6%) over the same time period [16]. 

So to boost crop yields without using unnecessarily more land, there are a few things we can do: reduce food waste, shift towards a more plant-based diet, and optimize trade so production moves from countries that are projected to have the highest habitat losses to countries where fewer species are threatened by extinction. But by far the most effective way to prevent future cropland expansion is, yes, using more fertilizers [14, 16].

So it’s pretty clear. The more fertilizer the better, right?

Not quite. 

At a certain level, plants can no longer take in any additional nutrients. For nitrogen, this is measured using the “nitrogen use efficiency” (NUE), which indicates the nitrogen amount in crops versus in the applied fertilizers. If the ratio is low, it means nitrogen is wasted.  Indeed, several countries use too much nitrogen fertilizers, including China, Mexico, Brazil, Colombia and Thailand, which could maintain their food production even with less fertilizer use [17]. Globally, only 35% of applied nitrogen is used by crops [35].

Overusing fertilizers means plants cannot completely make use of the nutrients, so they leak into the soil and water, causing toxic pollution (e.g., from ammonia leakage into water, causing the suffering and death of aquatic life [31]), soil and ocean acidification, and eutrophication (i.e., excess nitrogen and phosphorus in water, leading to plant and algae growth, ultimately killing aquatic life due to oxygen depletion) [1]. 

Currently, several new developments try to optimize fertilizer use, such as applying them according to sensor data and using coated fertilizers (i.e., fertilizers that release more nutrients into the soil and less into the environment) [6]. Other approaches include government regulations or removing monetary incentives for farmers in order to use less fertilizers. During the Green Revolution, many governments, especially those of low-income countries, started to subsidize fertilizers, which in some cases led to an over-use [17]. China is one example of a country having removed subsidies for fertilizers in 2008, thus lowering their overall fertilizer use (although it’s still really high) [1].

Apart from creating environmental damage, nitrogen fertilizers and their production emit lots of greenhouse gasses. Since most ammonia is produced with the Haber-Bosch process, it relies heavily on natural gas as a hydrogen source. Additionally, the Haber-Bosch process is very energy-intensive: temperatures of 400-500°C and pressure of around 100-300 bar are necessary to combine hydrogen and atmospheric nitrogen [14]. 96% of the required hydrogen for ammonia comes from natural gas. Around 3-5% of global natural gas production goes towards ammonia production, which constitutes 1-2% of global energy production [28]. All in all, fertilizer production is estimated to make up 5% of global anthropogenic greenhouse gas emissions. On top of that, when applying nitrogen fertilizers to the soil, they release nitrous oxide, which has 300 times more global warming potential than CO2 [1]. 

What does the future of fertilizers look like?

(The claims made in this part are somewhat shaky and I’m not very confident in what I’m saying, mostly because discussions about sustainable ammonia production are quite technical and far outside my area of expertise. But here you go anyway.)

A lot of what I’ve written above boils down to two facts: 

1. The world needs fertilizers to feed its (growing) population. 
2. We must find alternative ways to produce nitrogen fertilizers if we don’t want to rely on fossil fuels anymore . 

It seems like a substantial amount of R&D is happening around “green ammonia”. The need for a more sustainable way to make ammonia doesn’t only depend on fertilizers. Ammonia is also used in producing plastics, explosives and synthetic fibers [27]. Plus it could be a promising future energy carrier. Since ammonia could store energy from renewable sources in liquid form and is great to cheaply transport over long distances without much energy loss, it seems like a promising candidate to replace fossil fuels in shipping, power turbines, and maybe even jet fuel [22, 28]. Although batteries are another great way to store renewable energy, it cannot be used for large-scale transportation. Ammonia, in contrast, could be used to transport energy through pipelines and shipping and burn it in power plants, much like oil nowadays [22, 23]. This means sustainable ammonia could be key to more than just the fertilizer sector, leading to more investments and R&D in this space [28]. 

As I’ve written above, ammonia production with the Haber-Bosch process greatly relies on natural gas for hydrogen. So one alternative is to try to find ways to make renewable hydrogen, such as through water electrolysis (i.e., splitting water into hydrogen and oxygen using electricity), solar thermal cycles (i.e., using a solar-powered electrolyzer to split water into hydrogen and oxygen) or biological processes (i.e., using biomass as a renewable energy source for hydrogen production) [23, 28]. 

The other alternative is to skip the Haber-Bosch process altogether and find completely new technologies to produce ammonia, for example, through non-thermal plasma synthesis (i.e., producing ammonia with only water, air and electricity in an electrochemical cell) or by utilizing the kind of microorganisms which produce ammonia in nature [25, 28]. Some of these solutions could enable a more distributed and even on-site nitrogen fertilizer production, which could reduce transportation costs/energy as well as the complexity and vulnerability of large-scale fertilizer production systems (by contrast, 30% of ammonia is currently produced in large ammonia plants in China) [25, 27, 28, 29].

Unfortunately, most of these new technologies are not yet available at commercial scale and are still in their demonstration phase [27]. The UK and Japan run experimental wind-driven green ammonia plants, while the US and Australia already have green ammonia plants that can produce a couple of thousand tons of ammonia per year. However, all existing sustainable ammonia plants only produce a negligible fraction of the around 200 million tons of ammonia produced every year [22, 28]. There is still lots of progress to be made. This means in the coming years and decades, governments and producers are expected to move a lot more investment into R&D, farmers need to be enabled to practice more efficient fertilizer use, and researchers encouraged to do more early-stage technology research [27].

My takeaways and unanswered questions

In the social circles around me, fertilizers tend to have a primarily negative association and discussions typically revolve around the damaging effects of fertilizers on the environment (not that there are a lot of discussions about fertilizers going on around me anyway). I had never given much thought to fertilizers before but I come away from this research feeling very positive about them. I—and many others reading this—probably wouldn’t exist without them.

The most important takeaway for me is that more efficient food production in Sub-Saharan Africa would be a big deal and could improve the lives of many, both through reducing general undernourishment and the risk of famine as well as by enabling people to move out of farming and potentially earn more money in other jobs. Fertilizers are only one part of the equation but from my research it seems like it’s an important one.

Yet it appears like increasing crop yields and fertilizer use is a rather unexplored topic in EA. A quick look at the research published by some EA organizations (including Open Philanthropy, Rethink Priorities, Charity Entrepreneurship, Founders Pledge) shows that virtually none of them are talking about this issue. And food security topics on the EA Forum are mostly discussed regarding its relevance for longtermism, not in the context of global poverty.

The only EA-ish organization I could find which runs programs around fertilizers is One Acre Fund (recommended as one of the “best charities” by The Life You Can Save). They supply smallholder farmers in Sub-Saharan Africa with farming supplies, including fertilizers, and provide training, including how to efficiently apply them. The Center for Global Development and Innovations for Poverty Action both do research on agriculture and food security in Africa, however, I couldn’t find anything specific about fertilizers in their work. Both organizations received one or more grants from the EA Global Health and Development fund, but not for their agriculture-related projects. Lastly, the Clean Air Task Force does research on sustainable hydrogen and ammonia, primarily as part of their work on zero-carbon fuels.

I am curious to know the reasons for this lack of attention on increasing crop yields and fertilizer use within the EA global health and development sphere. Maybe I am missing something very obvious. But if not, a next step could be answering the following questions:

• Are fertilizers really the best way to boost crop yields in Sub-Saharan Africa?
• What prevents farmers from using (more of) them? 
• What are possible interventions to raise crop yields and increase fertilizer use? 
• What is the estimated cost-effectiveness of these interventions and how do they compare to top interventions in global health and development?

Thanks to Inge Siegl, Lukas Trotzmüller, Philip Popien, and Simon Haberfellner for their feedback on this post.

Sources

1. Wikipedia (Fertilizers)
2. Our World in Data, 2017 (How many people does synthetic fertilizer feed?)
3. Hinge, 2023 (Food security and catastrophic famine risks - Managing complexity and climate)
4. Statista Research Department, 2023 (Fertilizer industry worldwide - statistics & facts)
5. Statista Research Department, 2023 (Production volume of nitrogen fertilizer worldwide in 2018, by country)
6. World Bank, 2022 (Fertilizer volatility and the food crisis)
7. Wikipedia (Green Revolution)
8. Our World in Data (Crop Yields)
9. Our World in Data (Employment in Agriculture)
10. International Fertilizer Association, 2022 (Five fertilizer market dynamics that tell the story of 2022)
11. Our World in Data, 2017 (Yields vs. Land Use: How the Green Revolution enabled us to feed a growing population)
12. Our World in Data (Global Food Explorer, Cereal Yield)
13. Our World in Data, 2022 (Increasing agricultural productivity across Sub-Saharan Africa is one of the most important problems this century)
14. Smil, 2022 (The Modern World Can't Exist Without These Four Ingredients. They All Require Fossil Fuels)
15. Our World in Data, 2019 (Land Use)
16. Our World in Data, 2021 (To protect the world’s wildlife we must improve crop yields – especially across Africa)
17. Our World in Data, 2021 (Can we reduce fertilizer use without sacrificing food production?)
18. Our World in Data, 2021 (Do we only have 60 harvests left?)
19. Our World in Data, 2017 (Is organic really better for the environment than conventional agriculture?)
20. Halstead, 2021 (Are we going to run out of phosphorous?)
21. The Breakthrough Institute, 2012 (We’re Not Running Out of Fertilizer)
22. MacFarlane et al., 2020 (A Roadmap to the Ammonia Economy)
23. Yale Environment 360, 2022 (From Fertilizer to Fuel: Can ‘Green’ Ammonia Be a Climate Fix?)
24. International Energy Agency, 2021 (Net Zero by 2050. A Roadmap for the Global Energy Sector)
25. Jupiter Ionics, 2023 (Our Technology)
26. Our World in Data (Fertilizers)
27. International Energy Agency, 2021 (Ammonia Technology Roadmap)
28. Ghavam, Vahdati, Wilson & Styring., 2021 (Sustainable Ammonia Production Processes)
29. Du, Denkenberger & Pearce, 2015 (Solar photovoltaic powered on-site ammonia production for nitrogen fertilization)
30. Center for Global Development, 2016 (Can GMOs Play a Role in a New Green Revolution for Africa?)
31. Lewit-Mendes & Boddy, 2022 (What matters to shrimps? Factors affecting shrimp welfare in aquaculture)
32. ALLFED (Resilient food solutions)
33. Biteau, 2022 (The great energy descent - Post: 3 What we can do, what we can’t do)
34. Erisman, Galloway, Klimont & Winiwarter, 2008 (How a century of ammonia synthesis changed the world)
35. Our World in Data, 2021 (Excess fertilizer use: Which countries cause environmental damage by overapplying fertilizers?)
36. Wikipedia (Nitrogen fixation)
37. Our World in Data (Hunger and Undernourishment)
38. Our World in Data, 2017 (Famines)