SOx

Most of the oxides of sulphur (SOx) emissions from our operations come from our metal smelters, although some are also produced from our coal fired power stations. During smelting processes, metals are separated from the other materials in mined ore, such as sulphur.  SOx emissions are released to the atmosphere unless steps are taken to intercept it and transform them into a more environmentally friendly product.

SOx emissions have been associated with impacts on human health such as asthma, and it is also a cause of acid rain in the northern hemisphere. 

How we minimise the health risks

We identify and try to minimise air pollutant emissions and their potential impacts by applying our Air Quality Control Standard which calls for assessment and prioritisation of emission sources and requires installation of emission controls to ensure protection of ambient air quality.

For example, our Kennecott Utah Copper operation in the US, generates the majority of Rio Tinto's SOx.  However, 99.5 per cent of these potentially harmful SOx gases are captured and converted into a saleable product. Customers for this high quality sulphuric acid include gold, copper, uranium, and beryllium metal producers, fertilizer producers, chemical manufacturers, power plants, steel companies, farmers, and companies involved in water treatment. 

The efficiency of SOx capture equipment used across the Group and depends on the smelter's age and type.

Our results

Our SOx emissions (SO2 and SO3) are expressed as sulphur dioxide (SO2) equivalents.

• In 2007, we captured 94 per cent of the SOx gases generated at our operations and emitted 72 thousand tonnes. This is an improvement since 2006 when we captured 92 per cent of the SOx gases generated.   89 per cent of our emissions were from stationary sources such as smelters, refineries, roasters and concentrators (SRRC activities).  Compared to 2006, our SOx emissions increased by three per cent. This was mainly due to expansions at a number of Rio Tinto's Australian iron ore mining, transport and shipping operations.