ABSTRACT
The ventilated air from livestock buildings comprises a potential source of complaints from people living in the vicinity. In order to avoid the complaints it may be necessary to reduce the odour in the ventilated air. This may be achieved using biofilters. Very comprehensive development and evaluation of such filters have been made by Zeisig (2, 3).
The ventilation air from the barn is extracted by fans which blow the air into a duct. From this duct the air is released beneath a slatted floor upon which a ca 50 cm thick layer of peat has been placed. During the passage of the air through the layer of peat the odours are absorbed and converted by microorganisms to odourless substances.
The filter material should consist of peat mixed with heather in order to keep the air resistance low. If the peat filter is to give maximum odour reduction the peat must be moist.
Investigation concerning the effect of biofilters (4) showed that the concentrations of gases such as ammonia and hydrogen sulphide decreased by an average 50 %. At an optimum level the reduction was 80 %.
The investment cost for a biofilter was about 100 DM per pig in South Germany. As regards a Swedish filter the investment cost was ca 50 DM per pig.
