Nitrogen’s Role in Food Production and Climate Change Threat

The fear of food production being unable to keep pace with global population growth has long been entrenched in history.

In the 18th century, the English cleric Thomas Robert Malthus theorized that any economic gains would be outrun by population growth until food production could keep up.

Plants need nitrogen: one of their five basic requirements, along with potassium, phosphorus, water, and sunlight.

From the earliest days of agriculture, farmers knew that restoring nitrogen into their fields was the only way to prevent declining crop yields.  

Nitrogen is found in plants – when they die, the nitrogen they contain goes back into the oil. Manure and compost also contain nitrogen, and the roots of legume plants host bacteria that replenish nitrogen levels in the soil. That is why farmers would use peas or beans in their crop rotation.

It is in the atmosphere that nitrogen is most abundant – consisting of 78% of the air. Nitrogen gas, however, is in an unreactive form rather than a reactive state, which plants can utilize.

For thousands of years, crops must depend on the limited form of reactive nitrogen naturally found in soil and ecosystem.

For atmospheric nitrogen to become “biologically available” to plants, it would necessitate a human intervention to “fix” it into forms that plants can use, such as ammonia.

A hundred years ago, this problem led two German chemists, Fritz Haber and Carl Bosch, to develop a method to transform nitrogen in the air into fertiliser, known as the Haber-Bosch process (Smil, 1999).

Both men later won a Nobel Prize for their work, although, in Haber’s case, it has been controversial because many have considered him a war criminal.

The invention of nitrogen fertilisers was “the most important invention of the 20th century” (Viglione, 2022). Nitrogen fertilizer has increased crop yields many folds.

The extra nutrients added to crops have boosted the world’s population – from 1.6 billion people in 1900 to nearly 7.8 billion today.

Nitrogen fertiliser is estimated to support around half of the global population, thanks to the technological breakthrough that Fritz Haber and Carl Bosch pioneered.

Ritchie (2017) says:

Our World in Data shows how many people the synthetic nitrogen fertilizer feed after it became commercially available from 1910 onwards. According to the article, the global population has grown from 1.65 billion in 1900 to almost 7.4 billion in 2015. Since 1910 when nitrogen fertilizer became available, it has supported 42% of global births over the past century. By 2000, 44% of the global population was fed by nitrogen fertilizer, which had grown to 48% in 2008. By 2015, it is estimated that the nutrient supported around 3.5 billion people who would otherwise have died.

While the use of nitrogen fertilizer has undoubtedly brought a lot of good to the world – increasing crop yields and global population, the intensification of agriculture aided by synthetic nitrogen fertiliser has come at a great cost to the environment, climate, and health of humans, animals, and soils (Viglione, 2022).

Production of fertilizers for food production is responsible for around 1.4% of annual carbon emissions, and the use of synthetic nitrogen fertilizer also releases nitrous oxide, a gas that is 300 times more potent than carbon dioxide in warming the planet. The gas also depletes our ozone layer (Viglione, 2022).

Nitrogen fertilisers applied on fields can leach into soils and wash into rivers and other water resources, feeding algal blooms, releasing methane, and decreasing oxygen levels in the water that can kill fish and other aquatic organisms.

Nitrous oxide emissions from synthetic fertiliser use and other human activities have grown unabatedly for decades. A paper published in Nature Climate Change finds that global emissions have increased and grown faster than reported. The paper includes N₂O emissions reports per country and global fertilizer production. It finds that the fastest growth in nitrous oxide emissions occurred since 2009, and China and Brazil are the top two N₂O emitters.

While reducing the use of nitrogen fertilizer is challenging, meeting the Paris Agreement requires that nitrous oxide emissions decline between 10-30% by 2050 (Thompson, Lassaletta, Patra, et al., 2019).

Interestingly, it shows that the US and Europe’s emissions haven’t grown for over two decades, but their crop yields have increased or remained unchanged.

The IPCC’s sixth assessment report on mitigation also notes that the agriculture sector is a major nitrous oxide emitter from manure application, nitrogen deposition, and nitrogen fertiliser use”. Reducing nitrous oxide emissions can be achieved through “improved crop nutrient management,” the report says.

Regarding reducing nitrous oxide emissions, governments have a role to play by promoting the more responsible and efficient use of nitrogen fertilisers as enshrined in the International Code of Conduct for the Sustainable Use and Management of Fertilizers (Calvo, 2022). Governments can also push for the more significant application of organic fertilisers such as manure, compost, peat, etc.

Calvo (2022) says that promising scientific developments for alternative fertilizers are taking place.

Some scientists are working on perfecting a  process known as “biological nitrogen fixation,” where legumes such as peas, beans, or lentils, by using a particular type of soil bacteria called rhizobia, “reduce” or “fix” nitrogen from the atmosphere into a form that crops can use as a fertilizer (Calvo, 2022). Research and development in this area are still in their early stages.