Depending on which components have to be removed from the air, different air purification techniques can be applied. For the removal of dust particles, a dust filter can be used, for ammonia a chemical or biological air scrubber is usually used and odor components can be further removed by means of a biofilter. Often, a combination of different air purification techniques is used in series to efficiently remove all components.
The polluted air is sent through the air scrubber, where the air is constantly sprayed with water.
In a chemical air scrubber, the water contains an acid (sulfuric acid) that binds with the ammonia present in the air. The spray water from the chemical air scrubber is a recognized fertilizer.
A biological air scrubber contains a filter with a biofilm (bacteria). These bacteria convert the ammonia to nitrite and nitrate (nitrification), followed by conversion to nitrogen gas (denitrification).
Combination scrubbers also exist, with first a chemical and then a biological step. The chemical scrubbing step ensures the removal of ammonia; the biological step the removal of odor components.
In the case of a biobed, an air flow is sent through a bed of biological material (eg wood chips, peat, coconut or root wood, tree bark). The bacteria present in this biobed provide an odor reduction. For the proper operation of the system, dehydration of the material must be avoided. The biological material must be replaced every 2 to 5 years. Biofilters are often combined with air scrubbers as a pretreatment of the air.
Combined heat and power (CHP) is a process in which electrical energy (electricity) and useful thermal energy (heat) are produced in the same installation. The installation is powerd by of a fuel.
This can be, for example, biogas. The heat produced by combustion is first converted into electricity. This electricity can be for personal use or be injected into the electricity grid. The residual heat that is released during electricity production is used on plant itself.
Therefore, a CHP is a way to produce heat and electricity, in which the joint generation of heat and electricity ensures an optimal use of the energy present in the fuel.