The influence of an adsorbent bed height made of tree bark on ammonia emission reduction was investigated under two scenarios: for constant mass of adsorbent and for adsorbent mass as a function of bed height. In both cases, measurements were performed on adsorptive beds of comparable height; other experimental conditions are presented in the part of the paper dealing with research methodology. The choice of tree bark as adsorbent material has been dictated by the results of preliminary research that was conducted on other biodegradable adsorbents in order to fulfill the basic assumption, i.e. that such materials, saturated with ammonia, should serve as natural organic fertilizer in plant production. The amount of ammonia adsorbed on tree bark increased linearly with the increasing height of the adsorbent bed. These results were analyzed together with the data on reduced ammonia emissions, including the amount of adsorbed pollution and bed height. Moreover, the ratio of bed height to the adsorber inner diameter (h/d_w) was used in data analysis. For the given optimal height of an adsorbent bed, the most appropriate time for replacing tree bark is when breakthrough first occurs.