One of the two finisher production sites of pig farmer Karl Ole Jokumsen is situated within the boundaries of the village of Svejstrup, in eastern Jutland, Denmark. For him, it was necessary to reduce odour emissions around this 900 pig finisher barn.

For him, the solution was found in applying a new air cleaning device in his chimneys, a novel technique supplied by Danish pig farm equipment manufacturer Skiold.

The chimney is one of the first examples of the company's 'CleanTube' technique. In this farm, the chimney is used for testing, hence its height is slightly longer than usual. For this farm was chosen as it was a rather old pig house, with full slatted floors, in which ammonia presence was obvious.

Essential in this novel technique is the use of undulating super absorbing material (either perlite or glass fibre) which is placed vertically in the chimney.

According to the 'counter current principle', water is flowing down while 'polluted air' is moving upwards through the ventilation system. On top of the absorbing material, a layer of bacteria will form which will help degrade the ammonia (NH3) present in the farm odour to more useful nitrate (NO3), which will be transported down to the manure pit with the water.

NO3 will later be reduced to NH4 in the manure tank; which is a good fertiliser, explains Mathias Andersen, MSc in microbiology, innovation adviser from Agrotech, who invented the method, which is now patented. Similarly, the process degrades the highly odourous hydrogen sulfide (H2S) into sulfate (SO4).

In Svejstrup, the system is installed in the top of a pig house for 300 finishers. The light is used for a permanent camera which helps with observing the trial system.

A large 'saucer' hangs underneath the chimney to catch all the water that comes down from the top – and which will be transported to the manure pit. Catching the water is done here to monitor the amount of water used. Other instruments measure connectivity, pH and temperature as well.

Total water use per day is about 400 litres. In this picture, the water supply from above has temporarily been increased.

Outside, connectivity and pH values can be regulated. First results indicate encouraging results of about 75-80% of the air being cleaned. Even methane is reduced, Andersen indicates. This proves the bacteria do their work since methane is hardly soluble in water.

Skiold is planning to deliver two more units for additional farms in Jutland and hopes to start up industrial production during 2010. In addition, further testing will be done with implementing a similar system inside a manure pit to be able to more directly catch the odourous air.

This last development would be directly beneficial to pigs as they will be in fresher air and this may well have a positive effect on feed intake. In addition, the air will be less dusty.