Practical measures mount up

ST has met its environmental targets by systematically auditing its plants and identifying opportunities to cut resource and energy use. It is constantly experimenting with new processes and solutions to find novel approaches to dealing with problems.

Each site is required to develop its own "roadmaps" towards the corporate targets. A key feature of the company's approach is to collect examples of best practice and transfer them to other sites.

  • ST installed a variable speed compressor at its factory in Agrate, Italy. This allows the manufacturer to adjust the flow rate of compressed air supplied to the system rapidly to match the needs of the factory. Avoiding excess supply of compressed air saves around 385MWh per year. The $17,000 installation cost was paid off in under two years.

  • Another innovation at the Agrate plant was to introduce a free cooling system. In winter, the clean room's thermal load is dissipated by means of specially constructed cooling towers. The system cost $600,000 to install, but saves around 10,000MWh per year in cooling energy. The capital cost was paid off in 1.2 years.

  • ST's manufacturing plant in Malta is well on its way to achieving a 90% water recycling rate. It employs high-tech measures such as microfiltration to remove silicon dust after wafer cutting, and reverse osmosis ion-exchange resins to clean water from the plating process. In addition, the site uses more basic techniques like storing rainwater and using brine from the production process as toilet flush water.

  • Switching from conventional ion-exchange technology to electro-deionisation to produce ultrapure water for ST's Rousset site in France led to a 50% cut in sulphuric acid use and a 90% cut in sodium hydroxide. This has had knock-on benefits including fewer lorry movements, less need for storage space and cleaner effluents.

  • The company's Ang Mo Kio plant in Singapore spent $860,000 on a sulphuric acid recycling plant last year. This cut the factory's consumption by 500 litres a day - or 95% - and saves $500-600,000 per year. Meanwhile, simplifying the process at its Malaysia site saved over 200 litres of sulphuric acid per day.

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