Resume The Danish agriculture has changed in the last 100 years; it has developed from an intensive agriculture to a more moderated one that takes care of the environment. The agriculture has changed, because of fluctuating prices has required farmers to increase the production to maintain or get a higher profit. This has contributed to an increase in the number of specialized farms. The main environmental impacts caused by animal production are emissions to the atmosphere and emissions to ground and surfacewater originating from the animal manure. Odor making from pig production is one of the biggest barriers for expanding pig production units in Denmark. The odor produces discomfort in the neighboring environment. The agriculture structure has changed and become more influence by the environment, nature and landscape. For this reason have been developed new methods to help the farmers maintain a good environment. It has been developed different techniques for cleaning the air from animal farms and for control the odor produced by manure, slurry and animal waste. Biofiltration is one of these techniques that have gained most interest in the past years. The goal of this project is therefore to study how the physical characteristics of the biofilters influence the filter efficiency. It is therefore decided to study two different biofilter materials (soil and saw dust) with respect to ammonia removal capacity as a function of physical characteristics. The study will be carried out using laboratory scale biofilters supplied with an artificially made ammonia-air mixture. The experiments will determine both the physical (air permeability, bulk density and water content) and the biological (ammonia removal kinetics) properties of the selected biofilter materials. The analyses demonstrate that both materials are effective for removing ammonia from air. The results show also that the water content has influence in the ammonia concentration in the material biofilter after the experiments.