How do we make ammonium sulphate?

To reduce the ammonia levels within the reactors, the recycled liquids are first processed in an Ammonia Removal system called an ‘ammonia stripper’. In this process, the liquid digestate is heated, and the ammonia gas is removed from the liquids by spraying the digestate over a stream of air that carries away the volatile ammonia gas that is released from the heated liquids. 

The ammonia-rich air is then ‘washed’ in a separate stage with an acidic solution of sulphuric acid and water. This ‘scrubs’ the ammonia gas from the air and transfers it again into a liquid form that is called ‘ammonium sulphate’.

The two types of ammonium sulphate

There are two types of ammonium sulphate: ammonium sulphate liquid and ammonium sulphate crystal. The liquid sulphate is stored in large storage tanks and can be removed by road tankers to be used in other locations. The sulphate can be further processed in a crystallisation plant that evaporates the moisture to create an ammonium sulphate crystal. This crystal can be used as a dry fertiliser that is more concentrated. Therefore it is more efficient to transport than the ammonium sulphate solution.