Researchers are close to a copper-based solution to significantly limit sulphur emissions and odours from animal housing. The new technology could have a major impact on the environmental challenges facing the farming industry.

It’s hard to avoid unpleasant smells when you move around in the countryside, so it’s not surprising that obnoxious odours from emissions of ammonia and hydrogen sulphide are one of agriculture’s most pressing environmental challenges.

In fact, livestock production is currently responsible for a great deal of the air pollution in Denmark and therefore, since 2017, a team has been working on the Ecometa project, the purpose of which is to measure and limit emissions from modern pig and cattle housing units.

The team has just reached a golden milestone in their endeavours to limit emissions. They’ve managed to develop a new and improved technology to clean the air, and they’ve come up with an air scrubber that uses copper ions to remove foul-smelling hydrogen sulfide from the air.

”In our quest for an efficient air-cleaning process, we’ve discovered that copper ions dissolved in aqueous solution react surprisingly efficiently with volatile sulphur compounds. Contrary to our initial expectations, the copper used in the process doesn’t precipitate, but can be regenerated and reused to serve as a catalytic reagent,” says Postdoc Pernille Kasper.

Can also remove odours
In existing air-cleaning systems based on microbial oxidation in a water phase or in a biofilm surface, for example, the poor water solubility of hydrogen sulphide and organic sulphur compounds inhibits a high removal efficiency. However, copper ions react so fast that the reaction overcomes this limitation.

“A further advantage of the process is that, in addition to hydrogen sulphide, it removes certain smelly organic sulphur compounds called thiols, which are challenging for both biological processes and existing chemical scrubber processes. The new process can be built into a so-called air scrubber, which typically consists of a support material onto which the reactive solution is sprinkled. The solution is exposed to the polluted air as it trickles through the support material, and due to the fast reaction, the gaseous sulphur compounds are transferred to the solution and degraded,” says Associate Professor Anders Feilberg, who is heading the project.

Current research activities aim at achieving a better understanding of the reaction mechanisms and product formation, and this will enable optimisation of the process and its application in full scale.

Far cheaper than previous tech
The process will also be applicable for reducing sulphurous odorants emitted from biogas plants, wastewater treatment plants and sewer systems. As a part of the Ecometa project, the air-cleaning process will be tested in full scale at a commercial pig farm in collaboration with the Danish company, Agrifarm.

In addition to developing a prototype purification plant, the team is also working on monitoring ammonia vapours and odours.

“We’re developing some new measuring methods to control the technology and reduce ammonia emissions. We’re currently working on three different sensors that can all measure ammonia emissions from livestock housing far more cheaply than previously,” Associate Professor Feilberg says.

Streamlining operations
Today, Danish livestock housing is granted environmental approval to produce a certain number of animals depending on the production area of the housing. Approval does not take into account the actual emissions.

The purpose of the project is to provide farmers with an opportunity to monitor emissions continuously, and thereby produce a time-resolved image of the pollution situation. The project will also open up for the possibility to regulate farms based on actual emissions.

“If farmers are able to carry out accurate monitoring of ammonia and sulphur emissions from animal housing, they’ll be able to streamline their operations. Moreover, if they can clear the air of ammonia at the same time, and even collect it for fertilising purposes, they’ll also be able to significantly reduce their environmental impact. That’s the scenario we hope to achieve in this project,” says Anders Feilberg.