Most livestock owners would rather get rid of it, but for the civilian and the government it is the solution: ‘the air scrubber’. The air scrubber has been fairly standard in pig farming for several years now, however, it begins to find its way to other sectors as well. An air scrubber also offers possibilities for cattle- and goat owners for example. Because of increasing regulatory pressures, it becomes more and more attractive to acquire an air scrubber. Next to that, if there is ownership of land, it is possible to save on the supply of nitrogen.
Air Scrubbers can be divided into reverse flow, cross flow and direct flow wahsers because of the way in which the outgoing (filthy) stable air and the washing water flow through the filters of the scrubber. For livestock owners there are (next to the execution) three (allowed) washing systems available:
– Biological System
– Chemical System
– Combined System
A biological system uses micro-organisms (bacteria) in the washing water to eliminate the ammonia and odour from the air in the stables. The biological system results in an ammonia reduction of 70%, 45% odour reduction and 60 to 75% dust reduction.
A chemical system adds acid to the washing water which causes a decrease in the ph value and the removal of ammonia and odour from the air in the stables. The chemical system results in an ammonia reduction of 70 to 95%, 30 to 40% odour reduction and a 30% dust reduction.
A combined system consists of at least 2 combined washing systems which clean the outgoing air multiple times. A combined system can be both a biological or chemical system combined with a water washer and/or bio filter. A combined system results in an ammonia and odour reduction of 70 to 85% and an 80% average reduction of dust.
The air scrubber is usually placed at the backside of the stable; this can be on the ground as well as at height. It is also possible to place the scrubber in the top of the stabel; this has as an disadvantage that the roof needs to be adjusted (raises costs) while a steel construction needs to be build in the stable equipped with a carrier plateau with enough carrying capacity to carry an air washer in full use. A central suction duct will be made in the stable on which all the control/measurement valves of the rooms come out. The fans will be placed inside the wall between the central suction duct and the pressure room (which is between the duct and the air scrubber). The fans suck the warm/dirty air out of the stable and press it into the scrubber via the pressure room, where the air is then cleaned.
Most entrepreneurs think of the closed pig stables with a central suction channel when it comes to air scrubbers, but air scrubbers can be used just as well on an open stable. Veldman Techniek placed its first air scrubber in 2009, and in 2013 it placed the first scrubber on an open stable. People remain hesitant to work in a closed stable, even though it becomes more attractive because of strict regulations. An air scrubber can be taken into account when designing the stable, so it will work optimally. With an open stable, it is namely important that the openings closest to the scrubber remain closed the longest so no cross flow will come to exist (divide the ventilation curtains into segments).
The scrubber can also aid in heat recovery because of new developments. The principle behind this is fairly simple; the warm air from the stable heats the water in the washer to 16°C à 20°C. This water is then reduced to about 13°C by a heat exchanger; the extracted heat can be reused in the stable. This is especially interesting in pig stables, because more heat is generated and used here. Heat exchangers that can be used for this purpose are those that make use of air – air, water – water, or water – air.
The last couple of years there have mostly been negative stories about the chemical scrubber with regards to the acid and the acid resistance of your stable, but it is completely doable to choose for a chemical washer with some adjustments to your facade. The chemical washer has as an advantage that the purge water can withdraw much more ammonia, so in the end less water is needed and a more concentrated end product results.