Researchers unlock the secret of nitrogen fixation

Date: 12 June 2017

Introduction: Chemists from the University of Antwerp have discovered the underlying mechanism behind 'nitrogen fixation'. Nitrogen from the air can now be transformed sustainably into the basic building blocks of mineral fertilisers.

Nitrogen is an essential element for all forms of life, because it is necessary in the development (biosynthesis) of the basic building blocks – such as amino acids, proteins and nucleic acids – of plants, animals and all other life forms on earth. There is certainly plenty of nitrogen in the earth’s atmosphere: 78% of all the air in our atmosphere is composed of molecular nitrogen (N2).

“But this abundant source of nitrogen cannot be used for biosynthesis, because it is a very stable molecule”, explains Professor Annemie Bogaerts, head of the PLASMANT research group at the University of Antwerp. “Breaking the triple bond between the two N atoms requires a great deal of energy.”

The process in which nitrogen in the earth’s atmosphere is converted into simple nitrogen compounds, such as ammonia (NH3) or nitric oxides (NO, NO2), is called nitrogen fixation. Bogaerts: “This process is crucial for all life on earth. Many researchers have struggled with the question of how to achieve this most challenging step of nitrogen utilisation in biosynthesis in an energy-efficient and sustainable manner.”

Plasma is the key

The Antwerp chemists and their colleagues from the University of Eindhoven have now achieved a breakthrough, thanks to plasma. “Plasma is the fourth state of matter, or fourth aggregate state, besides solid, liquid and gas”, Bogaerts explains. “It can be generated either by heating a gas or by introducing electrical energy into a gas. An ionised gas is then formed, which consists of gas molecules and reactive particles such as ions, electrons and radicals. This cocktail of reactive particles produces new chemical reactions, such as the conversion of nitrogen into new compounds.”

The reaction of nitrogen with oxygen in a plasma generates nitric oxides, which can be converted easily into other basic building blocks for living organisms. “And because plasma is generated using electrical energy, it can be done in a sustainable way. All sustainable energy sources, such as wind and solar power, can be used to generate plasma.”

Remote areas

Bogaerts sees plenty of potential applications for this technology. “Farmers in remote areas, for example, can produce mineral fertilisers on site using wind or solar energy, as a sustainable alternative to conventional fertilisers. There are also opportunities in developing countries and in regions where sustainable energy is currently underutilised.”

This groundbreaking research was recently featured on the cover of ChemSusChem, one of the leading journals on sustainable chemistry.