Biological and composting processes used in the treatment of municipal solid waste typically are sources of odour pollution (gaseous pollutants include SO2, NH3, H2S and other toxic air pollutants). In this work, the removal of NH3 present in odorous composting leachate was assessed for the first time in a fixed-bed column loaded with carbonaceous adsorbents prepared by hydrothermal carbonization (HTC) assisted with sulphuric acid and by pyrolysis of carbon precursors (olive stone and malt bagasse). The resultant adsorbents were characterized to study their surface chemistry and textural properties. Scarce work studying the HTC in presence of additives, but H2SO4-assisted HTC allow to obtain acid hydrochars with accuracy properties for NH3 adsorption. In this work, the hydrochar prepared from olive stone by H2SO4-assisted HTC shows the highest NH3 adsorption capacity (11.4 mg g-1), evidencing that acidity contributes more significantly to the removal of NH3 than the specific surface area of the adsorbents. The NH3-saturated hydrochar was regenerated by washing with distilled water and subsequently re-used in the adsorption of NH3, obtaining satisfactory performance (68% of the mean NH3 adsorption capacity of its respective first use).