Sasol said some of its South African plants are under threat from sulfur dioxide emission standards that it will need to comply with by 2025. The company, South Africa’s biggest by revenue, operates plants that convert coal into motor fuel and chemicals in Secunda, east of Johannesburg, and Sasolburg to the south. Flue-gas desulphurisation equipment needed to cut emissions of the gas, which causes acid rain and a range of health complications, is too costly and technically difficult to install, Sasol said. Globally, as well as in South Africa, the company produces a range of chemicals.