Production of soda ash at a plant in Adelaide is to end in June. Stocks are to be imported in future.
The ABC reports Penrice Soda at Osborne is the only domestic producer of soda ash, also known as sodium carbonate, which is used to make glass, washing power, detergents and pharmaceuticals. It is also used as a food additive.
The company said the soda ash side of its business is unprofitable because of increased energy and labour costs, the high Australian dollar and rising taxes. It has formed a joint venture with SASS Victoria to sell imported soda ash.
Chief executive Guy Roberts said lower international shipping costs make imports much cheaper, driving down demand for domestically-produced soda ash.
The Osborne plant will continue to produce quicklime for use in cement.