A Scottish maggot farm, supplying bait for fishing, faced the problem of dealing with ammonia odours emitted during production. The Scottish Environmental Protection Agency (SEPA) had given the company an emissions discharge consent level of a demanding 5ppm of ammonia. To achieve this the maggot farm commissioned a biofilter to remove the pollutants from the air stream. The design of the biofilter required the air to be passed through a bed of organic material before being expelled from the building. The filter bed contained a mixture of organic materials including calcified seaweed. This media was then used as the media to hold Amnite N500 nitrifying bacteria provided by Cleveland Biotech. These bacteria convert the ammonia in the emissions from ammonia (NH3) to nitrate (NO3). The seaweed was important as it helped to maintain a neutral pH essential for the effective functioning of the bacteria. Since installation the biofilter has continued to ensure that maggot farm successfully meets the discharge consent limits of 5ppm with minimum maintenance requirements.