Air washer converting nitrogen into fertiliser aims to hit market next year

An improved air washer that converts nitrogen into fertiliser will "hopefully" hit the market within a year, its developers say. The new air washer uses much less water than existing technologies and would turn nitrogen into a profitable product.

The air washer, developed by KU Leuven university, is currently being tested on a controlled farm in Lovenjoel, a village in the Belgian province of Flemish Brabant.

Air washers are used to remove ammonia from the air at pig or poultry farms to prevent excess nitrogen from entering the environment. Existing chemical air washers use sulphuric acid, but this process requires a lot of water.

Important nutrients are also lost in the existing process. Scientists have therefore long been looking for new ways to develop more efficient air washers.

Circular economy for nitrogen

KU Leuven's new washer uses nitric acid instead of sulphuric acid. Plasma reactors, powered by air and electricity, chase tiny flashes of several thousand volts through ionised gas to produce the nitric acid needed.

"For the first time ever, we have managed to immediately recover nitrogen"

Treating ammonia in the air in barns with nitric acid produces ammonium nitrate, an important fertiliser. Farmers could immediately use this fertiliser on their own fields, or transport it to neighbouring farms or fertiliser manufacturers.

"For the first time ever, we have managed to immediately recover nitrogen: we have created a circular economy for nitrogen," said KU Leuven professor Johan Martens. "As a result, the chemical industry also needs to produce less fertiliser, which reduces the amount of fossil fuels needed for these processes."

10 times less water

After first testing the technology in a laboratory setting, the installation was brought to the TRANSfarm farm in Lovenjoel last year, in a barn with 30 pigs. Since then, the system has been refined and scaled up to a larger barn with 700 pigs.

The system could remove 2,375 kg of ammonia from the air each year

The system uses 10 times less water than current technologies and could produce 10 tonnes of ammonium nitrate per year for an average barn of 1,000 pigs. This would remove 2,375 kilograms of harmful ammonia from the air each year.

Market ready within a year

The technology has so far been tested in closed barns, but Hollevoet and Martens say it can also work perfectly in partially open barns if the unit is sized correctly. Barns with animals other than pigs should also pose no problems.

"This is ambitious, but it is also an urgent problem that we want to solve"

The researchers will now send samples of the ammonium nitrate produced to fertiliser manufacturers with the aim of getting their product certified and ready for the market. In this way, emitted nitrogen could be turned into a profitable product.

This should be possible within a year, said project manager Lander Hollevoet. "This is ambitious, but it is also an urgent problem that we want to solve," said Hollevoet.

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