Sulphur powder may save millions

Press, 17 July 1980, Page 2

Sulphur powder may save millions

PA Hamilton Research being conducted at the Ruakura Soil. and Plant Research Station could save New Zealand tens of millions of dollars spent annually on importing fertiliser sulphur. It could also result in the production of a cheape r phosphate fertiliser than superphosphate, called biosuper.

Announcing this yesterday, the scientist in charge of the project, Dr Sunder Rajan, said at present New Zealand was importing 230,000 tonnes of sulphur a year, valued at $4O million, for converting to sulphuric acid to make Superphosphate.

The new process using sulphur mined from Lake Rotokaua, near Taupo, used sulphur as a fine powder for mixing with phosphate, rock without further processing. The estimated quantity of this deposit was six million tonnes, equivalent in value to $1056 .million, and amounted to more than 25 years ■ supply for New Zealand, Dr Rajan said. f. D.S.I.R. scientists ' had been studying the extraction of this sulphur for the last 10 years for fertiliser user but because the material was of low purity it could not be used for producing superphosphate, without further costly processing. However, with : recent price increases, mining by a New Zealand company was now being considered, he said.

, The impurities in the local sulphur were no obstacle to making biosuper — a slowrelease but high-solubility phosphate and sulphate fertiliser..

Dr Rajan has already prepared biosuper and greenhouse trials .showed that it was as good as superphosphate, and was likely to have a longer-lasting effect because of its slow-release property.

The price of superphosphate has gone up by more than 50 per cent in four months, caused by big rises in the costs of raw materials, particularly sulphur, which has increased from $97.50 to $176 a tonne.

Dr Rajan said sulphur accounted for 27 per cent of the cost of superphosphate, and it was estimated its processing for biosuper would cost only half as much as the cost of converting it to sulphuric acid for superphosphate.