Modern agriculture relies heavily on synthetic nitrogen fertiliser, yet the way it is produced has changed remarkably little in more than a century. Most nitrogen fertiliser is still manufactured through the Haber–Bosch process, which combines nitrogen from the air with hydrogen derived largely from fossil fuels under very high temperatures and pressures.
Dr Doris Blaesing has reviewed three new emerging technologies that could fundamentally change this model. Researchers and companies are developing systems capable of producing ammonia or nitrate fertilisers using only air, water and renewable electricity.
However: None of these technologies are yet fully commercial at large scale, although some have progressed from laboratory research into pilot and early demonstration stages.
Plasma–electrochemical hybrid reactors (air + water → ammonia)
One of the most advanced emerging approaches combines plasma technology with electrochemical processing to produce ammonia from air and water.
These systems combine an electricity driven air plasma with an electrochemical reactor in a three step process:
- A non-thermal plasma first activates nitrogen and oxygen from the atmosphere, producing reactive nitrogen compounds such as nitric oxide and nitrogen dioxide (NO and NO2).
- These compounds dissolve into water as nitrate and nitrite.
- An electrochemical reactor then reduces the nitrate or nitrite into ammonia (NH3) using water as the hydrogen source.
The process operates at near-ambient temperatures and pressures and can run on renewable electricity.
Will it work?
Researchers have already demonstrated ammonia synthesis directly from air and water under ambient conditions, while recent studies have achieved relatively high faradaic efficiencies and improving energy performance.
Projects funded through ARPA-E, are also supporting the development of solid-state electrochemical membrane reactors designed specifically for ammonia production using renewable electricity.
Development stage
Although technically promising, these systems remain at laboratory to pilot scale. Major challenges include energy efficiency, catalyst durability and scale-up
In the future how suitable are they?
- Highly suitable for on farm deployment
- Good for regional systems
- Not ideal for centralised mega plants
- Very strong fit for broadacre and irrigated systems, especially where:
o Fertiliser logistics are costly
o Renewable electricity is available
o Liquid nutrients are already used
Limitations
- Low energy efficiency on a per kg N basis
- Produces oxidised nitrogen only (no urea or pure ammonia)
Plasma – liquid reactors (air + water → nitrate / nitric fertiliser)
These reactors use non-equilibrium plasma directly over or through water with two key steps:
- The plasma activates nitrogen and oxygen from the air, generating reactive nitrogen oxides (NOx)
- The (NOx) reacts in water to form nitrate (NO3-), along with smaller amounts of nitrite (NO2-)
Unlike plasma – electrochemical systems, no secondary ammonia conversion (electrochemical reduction) stage is required.
Will it work?
Research has shown that dielectric barrier discharge (DBD) plasma reactors can generate high concentrations of nitrate directly in water using only air, water and electricity. Continuous plasma–liquid systems producing nitrated water fertiliser have also been demonstrated with steadily improving energy efficiency. At the same time, ARPA-E–supported companies, for example Nitricity, are developing renewable-powered farm-scale plasma nitrate reactors aimed at local fertiliser production.
Development stage
These systems are currently at the pilot stage and could be particularly attractive for on-farm fertiliser projection.
In the future how suitable are they?
- Limited on farm but strong regional/decentralised hub option
- Can produce anhydrous ammonia or ammonium salts
- Avoid fossil hydrogen entirely
- Operate modularly (unlike Haber–Bosch)
- Suitable for renewable rich regions
Limitations
- Requires careful catalyst control
- Multi stage system (plasma + electrochemistry)
- Higher operational complexity
- Maintenance and diagnostics exceed typical farm capacity
Direct electrochemical nitrogen reduction Reduction (N₂ + H₂O → NH₃)
A third pathway under development is direct electrochemical nitrogen reduction, which attempts to produce ammonia directly from nitrogen gas, water and renewable electricity within a single electrochemical reactor.
Will it work?
Electrochemical ammonia synthesis using water and nitrogen has already been demonstrated with membrane reactors and ruthenium-based catalysts operating at moderate temperatures.
However, while numerous reviews confirm the technical feasibility of the approach, they also highlight ongoing challenges associated with competing hydrogen reactions and the difficulty of scaling the systems for practical large-scale use.
Development stage
In theory, this approach offers one of the simplest long-term routes to renewable ammonia production. Nitrogen gas and water are combined inside an electrochemical cell, where electricity drives the conversion to ammonia without the need for conventional hydrogen production.
However, the technology remains at an early research stage and relies on precise catalysts, tightly controlled operating conditions.
In the future how suitable are they?
- Not yet suitable on farm
- Experimental at regional scale
Limitations
- Require elevated temperature (200–300 °C)
- Use expensive catalysts and membranes
- Struggle with hydrogen side reactions
- Remain at lab or early pilot scale
The bottom line
There is no fully commercial reactor yet, but technically viable pathways already exist, and several are approaching real world deployment, especially for distributed, renewable fertiliser production.
