New insights for sustainable green ammonia production

Ammonia is a simple molecule, but it plays a critical role in feeding the world. As the main ingredient in fertilizers used to grow food for billions, ammonia helps sustain global agriculture. A new review published in Science China Chemistry shows that researchers are now exploring ways to make ammonia using renewable energy and sunlight instead of fossil fuels.

Today’s dominant ammonia manufacturing method — the Haber-Bosch process — relies on high temperatures and pressures as well as fossil fuels, making it energy-intensive and responsible for significant carbon emissions. The new review offers a hopeful outlook, highlighting several cleaner, more flexible production methods that could reduce emissions and enable smaller, decentralized ammonia synthesis facilities.

Promising green pathways to ammonia

The review identifies four emerging approaches:

• Electrocatalysis: Uses electricity (ideally from renewable sources) to drive the reaction under normal pressure and temperature. This method offers safe, modular systems suitable for smaller-scale fertilizer production, but efficiency must improve to reduce unwanted hydrogen side reactions.

• Photocatalysis: Uses sunlight alone to power the chemical conversion. This method could produce zero direct emissions, although current systems remain limited by low productivity and instability under prolonged light exposure.

• Photo-electrocatalysis: Combines electricity and light to improve performance, achieving higher ammonia yields than photocatalysis alone. It shows promise under milder conditions, but materials stability remains a key challenge.

• Photothermal catalysis: Harnesses light to generate localized heat and energetic electrons on catalyst surfaces, significantly increasing reaction rates while avoiding the extreme conditions of Haber-Bosch. Researchers are working to control heat localization and maintain catalyst integrity.

Turning pollution into a resource

The authors also highlight an alternative nitrogen source: instead of relying only on nitrogen gas from the atmosphere, scientists can use nitrate, nitrite or nitric oxide — these reactive nitrogen compounds are often found in wastewater or as industrial byproducts. Converting them into ammonia not only reduces pollution, but could also supply fertilizer more sustainably. In some lab systems, conversion efficiencies have exceeded 90%.

“Using waste nitrogen sources offers a dual benefit — cleaning up pollutants while producing valuable ammonia,” the review’s authors note.

Advances in catalysts and testing tools

To make green ammonia viable, the review records progress in designing advanced catalysts, including nanoscale structures, single-atom active sites, and hybrid materials, that promote ammonia formation while suppressing unwanted hydrogen production. Real-time measurement techniques and stricter testing protocols are helping researchers confirm that ammonia truly comes from the intended nitrogen source, a critical step for proving genuine success in clean ammonia production.

A Roadmap for green ammonia

The authors recommend a coordinated effort to:

• Develop more durable, selective catalysts

• Standardize testing methods and reporting protocols

• Integrate renewable energy sources with local production sites

With global demand for fertilizer rising and decarbonization becoming increasingly urgent, green ammonia could become a cornerstone of sustainable agriculture and clean energy.

“Advancing green ammonia production is critical not only for food security but also for a sustainable energy future,” the authors conclude.