Raw materials are usually purchased from an outside source or transferred from an onsite plant. Studying each raw material determines how it affects the amount of waste produced. Also, the specification of each raw material en tering the plant should be closely examined. The options described next can prevent pollution generated from raw materials.
Although the percentage of impurities in a feed stream may be low, it can be a major contributor to the total waste produced by a plant. Reducing the level of impurities involves working with the supplier of a purchased raw material, working with onsite plants that supply feed streams, or installing new purification equipment. Sometimes the effects are indirect (e.g., water gradually kills the reactor catalyst causing formation of by-product, so a drying bed is added).
Occasionally, a process uses off-spec materials (that would otherwise be burned or landfilled) because the quality that makes a material off-spec is not important to the process.
Impurities in a company's products can create waste in their customers' plants. Not only is this waste costly, it can cause some customers to look elsewhere for higher quality raw materials. A company should take the initiative to discuss the effects of impurities with their customers.
Inhibitors prevent unwanted side reactions or polymer formation. A variety of inhibitors are commercially available. If inhibitors are already being used, a company should check with suppliers for improved formulations and new products.
If the containers for raw materials being received cannot be reused and must be burned or landfilled, they should be changed to reusable containers or bulk shipments. Similarly, a company should discuss the use of alternative containers for shipping plant products with customers.
Sometimes a company can reduce or eliminate the need for a raw material (especially one which ends up as waste) by modifying the process or improving control. For example, one company cut in half the need for algae inhibitors in a cross-flow cooling tower by shielding the water distribution decks from sunlight.