What is nitrogen fixation, and how can we make it more sustainable?

Nitrogen is a fundamental building block of life. It is essential for the proteins, nucleic acids and chlorophyll that underpin living organisms. Nitrogen fertilizers are estimated to support about half the world’s population, enhancing plant growth and crop yields to feed an ever-growing world population.

However, the current method of extracting and converting nitrogen industrially – ‘nitrogen fixing’ – is both energy- and carbon-intensive, prompting a global push for greener alternatives.

The World Economic Forum has just named green nitrogen fixation as one of its Top 10 Emerging Technologies of 2025.

While nitrogen makes up 78% of the Earth’s atmosphere, atmospheric nitrogen (N2) is inert – non-reactive – and therefore unusable by plants. It needs to be ‘fixed’ by converting it into ammonia before plants can absorb it – a market predicted to grow at a rate of nearly 80% and reach more than $44 billion by 2032.

In nature, this happens through natural symbiosis between plants and nitrogen-fixing bacteria. To enhance nature's efforts and boost plant growth and yields, nitrogen must be chemically fixed at scale.

The vast majority of ammonia for the fertilizer industry is produced through the Haber-Bosch process, which was developed over a century ago. This method combines atmospheric nitrogen with hydrogen under high temperatures (around 500C) and pressures (above 100 bar) in a catalytic reaction.

Why are current nitrogen fixation methods bad for the environment?

While it has helped feed the world, the Haber-Bosch process is one of the most energy-intensive industrial operations, consuming between 1% and 2% of global energy. Most of this energy is needed for the production of hydrogen from natural gas – a fossil fuel.

This translates to significant greenhouse gas emissions: ammonia synthesis is responsible for 1.5% of global carbon dioxide emissions and also generates nitrous oxide (N20), a potent greenhouse gas released when fertilizers are applied to fields. N2O has a global warming potential about 300 times that of CO2.

However, to continue feeding a world population heading towards 10 billion by 2050, the need for fixed nitrogen will only grow.

New technologies are now emerging, promising to make nitrogen fixation more sustainable and less greenhouse gas-intensive.

Some efforts to ‘green’ the synthesis of ammonia go back to basics, looking at how nature fixes nitrogen using bacteria. By engineering bacteria that can fix nitrogen more effectively, crops can be paired with their own nitrogen-fixing partners. This could ultimately eliminate the need for synthetic fertilizers – and the associated emissions.

A seemingly unlikely candidate in this context is duckweed, which grows on ponds and swamps. It’s rich in protein and can double in mass every two days. Start-up Fyto grows duckweed in shallow pools of nitrogen-rich wastewater from dairy farms. Once harvested, the duckweed can be used directly as cattle feed or converted into sustainable fertilizer.

Other efforts focus on electrochemical nitrogen reduction using electrocatalysis with lithium, and updating the Haber-Bosch process to work with renewable feedstocks.

Decarbonizing ammonia production also ties in with a global drive to decarbonize hydrogen synthesis, the most energy- and emissions-heavy part of the process. Carbon-free ‘green’ hydrogen can be obtained from water electrolysis, using renewable or nuclear energy to split water instead of natural gas. To decarbonize existing fossil-fuel facilities, carbon capture technology can sequester CO2 before it enters the atmosphere.

However, despite global policy momentum, both methods currently represent a minimal share of overall production.

Beyond technology innovation, improved, sustainable agricultural practices can also help reduce the environmental impact of nitrogen fixation.

Legumes like peas, beans and lentils have some of the highest rates of fixation. Rotating these with crops that fixate less nitrogen can help enrich soils and reduce the need for fertilizer.

Precision farming can also significantly contribute to reducing the environmental impact of nitrogen fixation. Data-led insights and technology can help apply the right amount of fertilizer at the right time. The amounts spread can be minimized, eliminating waste and limiting environmental harm, from greenhouse gas emissions to soil acidification from high levels of retained nitrogen.

Greening nitrogen fixation lies at the crossroads of food security, climate action and sustainable development.

As green hydrogen and ammonia are set to decarbonize shipping and power generation on a large scale, the momentum generated here will likely also drive the fertilizer industry’s transition. Once these and other new approaches are rolled out in the field, they promise to address the increasing food demand more efficiently and sustainably.