Fisons Fertilizers Limited began in 1959 the manufacture of ammonium nitrate for use in Fisons compound fertilisers at their new site in Stanford-le-Hope, Essex. This nitrate salt provides nitrogen to the soil, one of the three essential elements of all plant food, as is used on the Agricultural industry as a main fertilizer. A starting material for the manufacture of ammonium nitrate, anhydrous ammonia of high purity (99.9 per cent minimum, with an oil content of 15 p.p.m. maximum), Fisons purchased this chemical from an adjacent plant operated by Shell Chemical Company Ltd at Shell Haven.
Here ammonia is made synthetically from the nitrogen of the air and from hydrogen obtained from oil by the Shell gasification process, it was delivered to the Fisons plant via a pipeline in the form of a liquid under pressure. The ammonia was stored on the Fison site in a 2,000-ton insulated spherical tank, the largest of its kind in Europe, at 4 bar. The raw material was then converted by two processes into ammonium nitrate. First, by catalytic oxidation followed by absorption to form nitric acid, and second, by neutralisation of the acid with further ammonia to produce a hot concentrated (88 per cent) solution of ammonium nitrate in water. This was then distributed by road and rail to Fisons compounding factories in various parts of the country. The plant closed sometime in the 1980s.