Biosolids may have their own distinctive odour depending on the type of treatment it has been though. Some biosolids have a stronger odour that may be offensive to some people, while most biosolids have a slightly musty, ammonia odour. Sulphur and ammonia compounds (both plant nutrients) in biosolids are normally the cause of these odours. Typically odours are reduced after the biosolids have been applied and incorporated into the topsoil. One of the objectives of biosolids management is to ensure that offensive odours minimised.