Fertilizer comes from a mix of mined minerals, fossil fuels, and biological waste, depending on the type. The three nutrients plants need most are nitrogen, phosphorus, and potassium, and each one has a completely different origin story. Some are pulled from the air, some from ancient rock deposits, and some from evaporated prehistoric seas.
Nitrogen: Made From Air and Natural Gas
Nitrogen is the nutrient crops consume in the largest quantities, and nearly all synthetic nitrogen fertilizer starts with two raw ingredients: the air we breathe and natural gas. The atmosphere is about 78% nitrogen, but plants can’t use it in that form. A century-old industrial process called the Haber-Bosch method fixes that problem by forcing atmospheric nitrogen to react with hydrogen (stripped from natural gas or other hydrocarbons) over an iron catalyst at extreme conditions: temperatures of 400 to 500°C and pressures roughly 100 to 300 times normal atmospheric pressure.
The result is ammonia, a simple molecule of one nitrogen atom bonded to three hydrogen atoms. Ammonia is the starting material for virtually every nitrogen fertilizer on the market. It can be applied directly to soil as anhydrous ammonia, or processed further into urea, ammonium nitrate, or liquid fertilizer blends. The process is energy-intensive because breaking the triple bond in a nitrogen molecule requires enormous force, which is why fertilizer production accounts for a significant share of global natural gas consumption.
Phosphorus: Mined From Ancient Rock
Phosphorus fertilizer comes from phosphate rock, and there is no alternative source. These rocks formed over millions of years as phosphorus-rich sediments accumulated on ancient ocean floors, eventually compressing into mineable deposits. Today, the rock is extracted through open-pit or underground mining, then treated with acid to convert it into a form plants can absorb, most commonly as superphosphate or diammonium phosphate.
The largest phosphate reserves sit in Morocco and Western Sahara, which hold the majority of the world’s known supply. Other significant producers include China, the United States, and Russia. Global phosphate rock reserves total an estimated 74 billion metric tons, with broader resources exceeding 300 billion tons. The U.S. Geological Survey reports no imminent shortages, but because phosphorus can’t be manufactured synthetically, the long-term availability of these deposits matters for global food security.
Potassium: Residue of Evaporated Seas
Potassium fertilizer, sold commercially as potash, originates from evaporite deposits left behind when ancient seas and inland bodies of water dried up. As seawater evaporated over geologic time, dissolved minerals precipitated out in a specific sequence: first carbonates, then sulfates, and finally chlorides. Potassium salts like sylvite were among the very last minerals to crystallize, meaning they only formed where evaporation was nearly complete. These deposits now sit deep underground in layers that can be hundreds of millions of years old.
Extracting potash involves either conventional underground mining or solution mining, where water is pumped into the deposit to dissolve the salts, then brought back to the surface for processing. In some locations, like Utah’s Great Salt Lake, companies harvest potash by evaporating surface brine in massive solar ponds. Great Salt Lake Minerals Corporation alone produces more than 400,000 tons of potassium sulfate per year using this method.
Canada dominates global potash production, mining roughly 15 million metric tons in 2024 and serving as the world’s leading exporter. Russia and Belarus are the next largest producers at around 9 million and 7 million tons respectively, though Belarusian exports have dropped significantly since 2022 after Lithuania cut off its port access. China and Germany round out the top five.
Organic Fertilizers: Animal and Plant Waste
Before synthetic chemistry, all fertilizer came from living things, and organic fertilizers still follow that principle. The most common source is livestock manure from cows, chickens, and horses, which contains all three major nutrients in varying concentrations. Manure works as both a fertilizer and a soil conditioner, adding organic matter that improves water retention and supports beneficial microbes.
Beyond manure, a range of animal byproducts serve as targeted nutrient sources. Bone meal, made from ground animal bones, is rich in phosphorus. Blood meal, a dried slaughterhouse byproduct, delivers a concentrated dose of nitrogen. Fish emulsion, feather meal, and composted food scraps each contribute different nutrient profiles. On the plant side, alfalfa meal, kelp, and wood ash have long been used to feed soil. These materials release nutrients more slowly than synthetic fertilizers because soil organisms need to break them down first, which means they’re less likely to cause nutrient runoff but also take longer to show results.
The Guano Era: How It All Started
The modern fertilizer industry traces its roots to bird droppings. In the early 1840s, seabird guano from Peru’s Chincha Islands became the world’s most prized fertilizer. Produced by cormorants, boobies, and pelicans over centuries, the excrement had remarkably high nitrogen content because the dry coastal climate preserved it. American farmers, especially tobacco growers in the mid-Atlantic, found their crop yields could triple with a single application, and they lobbied Congress aggressively to secure more supply.
The boom was short-lived. Guano from rainier islands lost much of its nitrogen to weathering, making it far less effective. By the 1870s, supply was dwindling, and by 1880 the world’s known guano deposits were effectively mined out. The seabirds, displaced by mining operations, couldn’t replenish what had taken millennia to accumulate. Around the same time, large deposits of nitrates and phosphates were discovered on land, allowing fertilizers to be blended for specific soil needs. The guano era ended, but it established the commercial principle that would drive the fertilizer industry forward: that crop yields depend on replacing the nutrients harvests remove.
Green Ammonia and Renewable Production
The biggest environmental cost in fertilizer production is the natural gas used to make nitrogen fertilizer. Green ammonia aims to change that by replacing fossil-fuel-derived hydrogen with hydrogen produced through water electrolysis powered by renewable energy. The hydrogen still goes through the Haber-Bosch process to become ammonia, but the carbon footprint drops dramatically.
Two main electrolysis technologies are competing for this space: alkaline electrolysis, which is cheaper today, and solid oxide electrolysis, which is projected to become more cost-effective as the technology matures. Current estimates suggest green ammonia could reach a cost of around 495 euros per ton by 2050 if electricity prices stay low. That’s still more expensive than conventional ammonia, but the gap is narrowing as renewable energy costs continue to fall.