Danish Pig Research Centre: Annual Report 2010: Environmental Technology

by 5m Editor
30 September 2011, at 12:00am

The 2010 annual report from the Danish Pig Research Centre outlines the latest research on pig house environmental management.

Testing of environmental technology

Pig Research Centre (PRC) participates in the development and testing of environmental technologies used by pig producers to limit ammonia and odour emissions. The aim is to ensure that these technologies are efficient in terms of their environmental impact as well as the economy in using them.

A ‘technology list’ made by the Danish Environmental Protection Agency outlines the systems that have already been tested sufficiently (see the table), while PRC is continuously testing new products and technologies. A wide range of methods is available for reduction of ammonia emissions from pig houses whereas only few reduce odour emissions. Below, current investigations of new or improved environmental technologies are described.

Dorset air cleaner

Rotor A/S, a Danish ventilation company, markets a biological air cleaner from the Dutch company Dorset. The air cleaner is approved for use in the Netherlands and Germany, but foreign trials revealed that the consumption of water and the production of discharge water were too high for the air cleaner to be used on pig farms in Denmark.

The air cleaner was therefore modified and in 2009 set up on a Danish finisher farm where PRC tested its efficiency in reducing ammonia and odour over a year.

Data shows that both the consumption as well as the discharge of water were successfully reduced. The air cleaner also reduces emissions of both ammonia and odour under Danish production conditions. The results of the trial will be published in the autumn 2010.

Three-step air cleaner from SKOV A/S

For years, Danish pig producers have been using the Farm AirClean BIO system, a biological air cleaning system from SKOV A/S. Through trials, PRC has demonstrated that odour concentrations dropped by 30 per cent in the summer and by 50 per cent in the winter when ventilation air from pig houses was cleaned. Ammonia concentrations of 4-9 ppm were reduced to 1-2 ppm.

Technology list of the Danish Environmental Protection Agency of approved environmental technologies and their efficiency in reducing ammonia and odour emissions from pig houses.
Technology NH3 Odour
Feeding efficiency 10-20% 0
Reduced protein 15% if 10% less crude protein 0
Benzoic acid 1% per g/feed unit 0
Slurry technologies
Cooling of slurry 30% 0
Acidification of slurry 70% 0
Air cleaning
Air cleaning with acid 90% 0
Biological air cleaning 70% 0

SKOV A/S has improved the system to increase the reduction in odour. The controller was optimised and the washing robot in the air cleaner modified. Furthermore, a third filter element was installed, ie. the air cleaner may consist of three vertical cellulose filters if large odour reductions are required. To ensure that all filters are evenly loaded with air, a perforated air distribution board is fitted before the first filter element.

Recordings made in Germany in 2009 indicate that the air cleaner is improved in terms of odour reduction. PRC is now investigating the air cleaner to document the reduction in ammonia and odour and the costs of running the system on a Danish finisher farm.

Air cleaner from Munters A/S

Air cleaner with acid from Munters A/S.

In the summer 2009, PRC made a series of preliminary recordings of an air cleaning system developed by Munters A/S (previously Turbovent) that demonstrated a 90 per cent reduction in ammonia. The system was subsequently modified by Munters A/S, and is now ready for a comprehensive test. The aim is to document its efficiency in reducing ammonia emissions over a long period of time and the costs of running the system.

The air cleaner is constructed as a tube without filter elements. Nozzles at the bottom of the air cleaner sprinkle acidic water into the air stream whereby air is cleaned. A drip catch at the top of the system retains the acidic water in the air cleaner.

It remains to be clarified if acidic water is released with the exhaust air from such systems to potentially damage building parts. Part of the investigation of Munters’ system thus concerns the amount of acidic water released from air cleaner to the surrounding environment.

Cooling of inlet air

Odour emissions from pig houses are highest in the summer when ventilation systems run on maximum performance. In an investigation of a ground cooling/heating system from the Dutch company INNO+, it was therefore determined whether ammonia and odour emissions could be reduced when the inlet air in a farrowing house was warmed or cooled, respectively, so that the ventilation rates in the housing unit varied less. Over a year, the system was capable of keeping the temperature of the inlet air to the farrowing house between 4.3 and 19.6 C° despite the fact the outdoor temperatures ranged from -4 to +32 C°.

Odour emissions from the trial facility generally tended to be lower in the summer. However, on the hottest summer days, odour emissions from the trial facility were 39 per cent lower than from the control facility, which shows that cooling the inlet air may neutralize the release of very high odour emissions in warm weather. It was not possible to record a significantly lower ammonia emission over an entire year.

Pit ventilation

Ammonia and odour originate from slurry, and PRC investigated if the majority of these substances can be collected in air that is emitted through pit ventilation. If so, a large reduction in ammonia and odour emissions from pig houses will be possible by cleaning this air with an efficient air cleaner.

Odour emissions may be reduced by frequently emptying slurry pits.

It was studied how much odour and ammonia emission originates from pit ventilation and ceiling exhaust, respectively, at a pit ventilation capacity of 16 and 54 m3/h per pig place, respectively. The remaining ventilation air up to maximum output (100 m3/h) was emitted through the ceiling.

The results demonstrated that when 16 m3/h were sucked out through pit ventilation, 61 per cent of the overall odour emissions and 70 per cent of ammonia emissions from the pig house originated from the pit ventilation.

When 54 m3/h were sucked out trough pit ventilation, 90 per cent of odour emissions and 94 per cent of ammonia emissions were collected in the pit ventilation. Here the overall emissions of both odour and ammonia from the pig house were significantly higher than during pit ventilation at 16 m3/h, and higher than expected. The most realistic way forward is therefore setting pit ventilation at approx. 10-20 per cent of maximum capacity.

The working environment in the pig house was equally good with both settings evaluated on the basis of ammonia and odour concentrations in the room.

Frequent emptying of slurry pits

In 2009, PRC investigated whether it is possible to reduce odour emissions from pig houses with slurry systems by changing the frequency of emptying of the pits.

In a trial section, slurry was emptied once a week, whereas it was emptied in the control section when the pits were full (40 cm). In the period June-November, 50 per cent lower odour emissions were recorded the day after the trial section was emptied compared with the control section. However, there was no significant difference in ammonia emission from the section regardless of emptying strategy.

The investigation is currently being repeated in the climate chambers at PRC’s Experimental Station Grønhøj where it is being studied for how long the reduced odour emissions last after emptying.


Infarm A/S is the only company with a Technology Sheet on acidification of slurry with 65-70 per cent reduction in ammonia emission from pig houses.

In the summer 2010, the company Jørgen Hyldgård Staldservice A/S installed its first acidification system on a finisher farm where PRC will test the system.

Further Reading

- Go to our previous article on this report by clicking here.

September 2011