For over a century, our ability to feed the world has depended on a chemical process powered by fossil fuels. Now, science is forging a sustainable new path forward.
Published: June 2024 | Reading time: 8 minutes
Nitrogen is fundamental to all life on Earth, forming a crucial component of our DNA, proteins, and cellular structures. A staggering 80% of our atmosphere is composed of nitrogen gas7 . Yet, in a profound irony, neither plants, animals, nor humans can directly access this abundant resource. We are, quite literally, swimming in a sea of nitrogen we cannot use7 .
Despite nitrogen making up 78% of our atmosphere, most organisms can't use it directly. This "nitrogen paradox" was only solved in the early 20th century.
This paradox was solved in the 20th century by the Haber-Bosch process, a technological marvel that extracts nitrogen from the air to create fertilizer, ultimately enabling the population explosion of the modern era1 . However, this solution came at a cost: the process is incredibly energy-intensive, consuming 1-2% of the world's annual energy output and generating about 1.9 metric tons of CO2 for every metric ton of ammonia produced1 . Our world's food supply is built on a foundation of fossil fuels.
But a revolution is brewing. In a landmark effort, top scientists convened by the U.S. Department of Energy have mapped a future beyond this fossil fuel dependency7 . This is the story of moving beyond fossil fuel-driven nitrogen transformations.
The Haber-Bosch process, often called the most impactful invention of the 20th century, works by breaking the powerful triple bonds that hold nitrogen molecules (N₂) together and combining them with hydrogen to form ammonia (NH₃)1 . This reaction requires extreme conditions—temperatures around 700 Kelvin and pressures of roughly 100 atmospheres1 .
Consumes 1-2% of global energy and produces 1.9 tons of COâ‚‚ per ton of ammonia.
Creates logistical challenges, especially in developing regions with poor infrastructure.
The most problematic part, however, is the hydrogen source. Typically derived from natural gas, hydrogen production is the primary reason the process has such a heavy carbon footprint1 . Furthermore, the centralized nature of these large chemical plants creates logistical challenges, particularly in developing countries where transportation infrastructure is poor and capital for building plants is insufficient1 . In all of East Africa, for example, there are no large-scale ammonia production facilities1 .
Moving beyond fossil fuels requires a diverse arsenal of scientific approaches. Researchers are not seeking a single magic bullet, but a suite of complementary technologies.
This approach focuses on improving the traditional process itself. Scientists are designing new, more efficient catalysts that could operate effectively at lower temperatures and pressures, dramatically reducing energy needs1 .
Nature has been fixing nitrogen for billions of years without fossil fuels. Microbes do this using an enzyme called nitrogenase1 . Scientists are now exploring how to harness and engineer this natural power.
Perhaps the most revolutionary ideas involve using renewable electricity or sunlight to power nitrogen transformation directly. USU biochemist Lance Seefeldt and his team have already pioneered a clean, light-driven process for converting nitrogen to ammonia7 .
"It's a potential game-changer," says Lance Seefeldt about the light-driven process for nitrogen conversion7 .
While many approaches focus on producing ammonia, a 2024 breakthrough from the University Alliance Ruhr in Germany tackled the next logical problem: how to efficiently use it.
The research team, led by Professors Wolfgang Schuhmann and Corina Andronescu, set out to create a catalyst that could convert ammonia into two valuable products simultaneously: hydrogen fuel and nitrite, a fertilizer precursor6 . Their experimental procedure was as follows:
They conceived a novel system that combined the reverse Haber-Bosch reaction with an electrolysis of water. Instead of just producing nitrogen and hydrogen from ammonia, their process would consume ammonia and water to produce nitrite and hydrogen6 .
A key innovation was the use of gas diffusion electrodes. Unlike previous methods where ammonia was used in dissolved form, their design allowed ammonia gas to be fed directly into the reaction6 . "This had never been done before," emphasizes Schuhmann6 .
The team employed multi-metal catalysts developed in their earlier work to overcome the major thermodynamic challenge: the strong tendency for ammonia to convert back into inert nitrogen gas instead of the desired nitrite6 .
The experiment was a resounding success. The team's catalytic system successfully bridged the "thermodynamic Grand Canyon," achieving a remarkable 87% Faradaic efficiency for nitrite production6 . This metric means that 87% of the electrical energy used in the reaction went toward creating the valuable nitrite product, rather than wasteful by-products.
The implications are profound. This single process can now produce both a clean energy carrier (hydrogen) and a fertilizer precursor (nitrite), effectively combining two industrial processes into one. Furthermore, the hydrogen yield is doubled compared to the conventional method of processing ammonia6 .
| Feature | Traditional Reverse Haber-Bosch | New Dual-Use Catalysis |
|---|---|---|
| Products | Nitrogen (Nâ‚‚) & Hydrogen (Hâ‚‚) | Nitrite (NOâ‚‚â») & Hydrogen (Hâ‚‚) |
| Hydrogen Output | Baseline | Doubled6 |
| Fertilizer Production | No | Yes, produces nitrite6 |
| Economic Value | Only hydrogen is usable | Two valuable, marketable products |
| Electron Efficiency | N/A | 87% directed to nitrite6 |
Interactive Chart: Efficiency Comparison of Nitrogen Transformation Methods
The tools for studying and improving nitrogen transformations are as diverse as the approaches themselves. Below is a look at some of the key reagents and materials driving this research forward.
| Research Reagent/Material | Function in Nitrogen Transformation Research |
|---|---|
| Multi-metal Catalysts | Critical for enabling novel reaction pathways, such as the conversion of ammonia to nitrite instead of nitrogen, by optimizing surface binding energies6 . |
| Gas Diffusion Electrodes | Allow gaseous reactants like ammonia to be efficiently fed into electrochemical cells, increasing reaction rates and efficiency6 . |
| Nitrogenase Enzymes | The natural catalyst from microbes; studied to understand and mimic its efficient mechanism for breaking Nâ‚‚ bonds at ambient conditions1 8 . |
| CRISPR-Cas9 Systems | Used to genetically engineer microbes (e.g., cyanobacteria, E. coli) to reprogram their nitrogen metabolic pathways for enhanced fixation or assimilation8 . |
| Metallocene Complexes | Soluble molecular catalysts that can mediate proton and electron transfer to nitrogen, enabling fixation at lower driving forces4 . |
Despite the exciting progress, the path forward is not without obstacles. The German team's dual-use catalyst, for instance, is still far from industrial implementation6 . More broadly, challenges include finding catalysts that break traditional scaling relationships, efficiently reproducing oxygen-sensitive enzymes for industrial use, and integrating complex multi-omics data to fully understand microbial communities1 8 .
Key Innovation: Using hydrogen from water electrolysis powered by renewables.
Potential Impact: Eliminates COâ‚‚ emissions from ammonia production1 .
Key Innovation: Using nanomaterials to capture light for nitrogen fixation7 .
Potential Impact: Enables decentralized, solar-powered fertilizer production.
Key Innovation: Using hydrogen-oxidizing bacteria to make food from air and electricity.
Potential Impact: Decouples protein production from agriculture and fossil fuels8 .
Key Innovation: Converting ammonia into both hydrogen fuel and fertilizer6 .
Potential Impact: Creates a circular economy, maximizing value from stored ammonia.
The future of nitrogen chemistry is taking shape. It is a future powered by sunlight and wind, where fertilizers and fuels are produced locally and sustainably, freeing one of life's most essential processes from its fossil fuel shackles. As the scientific community continues to innovate across disciplines—from heterogeneous catalysis to synthetic biology—the vision of a circular, sustainable nitrogen economy is steadily becoming a reality.
References will be listed here in the final version.