Oil refinery waste becomes fertiliser to boost grass and curb pollution

A new form of fertiliser which can boost grass yields by as much as 20 per cent and reduce farm pollution has been developed by the agricultural research body, Teagasc.

The product uses a sulphur byproduct from the oil refinery at Whitegate, Co Cork, combined with ground limestone from Carlow. It is designed to improve both the production yield and quality of grassland soils, and reduce the potentially harmful effects of established plant nutrients, which are largely composed of phosphorus and nitrogen.

Dr Matt Murphy, who devised the product at Teagasc's research centre in Johnstown Castle, Co Wexford, yesterday outlined its benefits. A pilot project is being conducted on a farm in Borrisokane, Co Tipperary, where yesterday's announcement was made.

While the sulphur-lime product is not yet commercially available, Mr Sean Hennessy of Irish Refining Plc said his company was interested in discussions with fertiliser manufacturers or other farm suppliers with a view to production and marketing.

The refinery produces between 700 and 1,000 tonnes of sulphur a year and is determined to use it as a value-added, rather than waste, product. "We are very impressed by the yields. The product really is showing great potential", Mr Hennessy said.

Mr Vincent McCarthy, the farmer who is evaluating the product, said, "It is proving to be a highly efficient source of plant-available sulphur and has increased herbage yields by over 20 per cent."

As a plant nutrient and soil conditioner it is exceptionally environmentally-friendly, said Dr Murphy. Sulphur incorporated into fertiliser can be oxidised and released into the atmosphere as harmful sulphur dioxide.

With the new product, this does not occur and sulphur is held in the soil before absorption into grass. It is converted to sulphate form by soil bacteria and made readily available to the plant.

If commercial development proves possible the product would need to be applied annually in spring, as sulphur is easily leached from the soil and is not retained beyond a growing season.

There is general agreement that phosphorus and nitrogen are responsible for increasing pollution of Irish lakes and rivers, he added. Steps have been taken to reduce their use in fertilisers, while at the same time soil scientists have long been concerned that grassland production and quality are restricted by sulphur deficiency and low lime status. The product would serve a useful purpose on both fronts.

Teagasc research suggests that more than 30 per cent of Irish soils are sulphur deficient, and these would benefit particularly from the sulphur-lime mix.

At present, most of the element is applied in sulphate form but in combination with nitrogen-containing fertilisers. Lime promotes the growth of clover and good grass species by increasing the availability of soil nitrogen, reducing acidity and the toxic effects of manganese, iron and aluminium.

Teagasc was asked in 1996 by Irish Refining to find a useful purpose for the sulphur by-product generated from its refinery. This contains over 96 per cent sulphur in elemental form, with about 30 per cent moisture.

Field trials showed that applying it in this pure form was sufficient to prevent sulphur deficiency. But because of its high moisture content and very fine texture, and as only a small amount is needed per hectare, it appeared to have little practical use as sulphur fertiliser.

Teagasc contacted Clogrennane Lime in Co Carlow and after several attempts to get the lime-sulphur mix right, an effective combination was established.