Does Fertilizer Impact Climate Change?

Written By Teacher: Teresa Pettitt-Kenney

Hi there! My name is Teresa and I just finished my Bachelor's degree in Environmental Science and am excited to pursue environmental education in the future! I am extremely passionate about climate change, equitable climate action, and how education can work to address these issues. 

The idea that fertilizer—something that helps plants grow—could be bad for the environment may seem counterintuitive to students. Investigate the benefits and drawbacks of fertilizers and connect how changes in farming can help the fight against climate change to make the discussion exciting, relevant, and engaging. Keep it light and silly by exploring all types of fertilizer, including this video about Transforming Human Poop Into Eco-Friendly Fertilizer.

Written By: MIT Environmental Solutions Initiative

The MIT Climate Change Engagement Program, a part of MIT Climate HQ, provides the public with nonpartisan, easy-to-understand, and scientifically-grounded information on climate change and its solutions.

Farmers add fertilizers to their soils to provide crops with the nutrients they need to grow. For thousands of years, humans have used mineral and organic fertilizers, like manure and ground bone, to improve soil fertility.

In the last century, human-made fertilizers have greatly boosted crop production, letting farmers grow more food on less land. But this uptick in fertilizer use has come at a cost: planet-warming greenhouse gas emissions. Worldwide, agriculture is the second-largest source of climate change pollution—and both the manufacturing and application of fertilizer has a heavy emissions toll.

Climate toll of fertilizers

One of the main nutrients that plants need to grow is nitrogen. But plants can’t take in nitrogen from the air the way they can absorb carbon dioxide or oxygen. In the early 1900s, scientists invented a process to mass-produce a nitrogen-containing compound, ammonia, that plants can absorb from the soil. Today, ammonia is the second-most commonly produced chemical in the world, used in huge quantities as a very effective fertilizer.

This invention revolutionized farming, doubling the number of people that one acre of land could feed. But ammonia has to be made at a high pressure under high temperatures—meaning it takes a lot of energy to manufacture. Most of that energy comes from burning fossil fuels like coal and methane gas, which give off the greenhouse gas carbon dioxide, the main cause of climate change. Ammonia manufacturing today contributes between 1 and 2% of worldwide carbon dioxide emissions.

Fertilizers also produce greenhouse gases after farmers apply them to their fields. Crops only take up, on average, about half of the nitrogen they get from fertilizers. Much of the applied fertilizer runs off into waterways, or gets broken down by microbes in the soil, releasing the potent greenhouse gas nitrous oxide into the atmosphere. Although nitrous oxide accounts for only a small fraction of worldwide greenhouse gas emissions, pound for pound, nitrous oxide warms the planet 300 times as much as carbon dioxide.