AT THE END OF THE DAY, THERE'S NOT MUCH LEFT FOR THE LANDFILLS.
Nucor is the largest recycler of scrap iron steel in North America. But not many people realize that there are vast amounts of by-products that others recycle from Nucor's steel-making process.
As an example, take a look at the recyclables generated by Darlington, South Carolina, a typical Nucor mini mill that produces approximately one millions tons of steel a year.
To keep up with the mill's demands, that plant must collect, cool, treat and recycle approximately 35,000 gallons of water every minute. In one day, the treatment plant saves enough water to take care of the needs of a city of 500,000 people.
First, there's mill scale, also known as iron oxide. As the red-hot steel cools, the surface oxidizes or rusts. As part of the finishing process, this rust is washed off with high-pressure water jets. Later, as this water is treated for re-use, polymer flocculants are used to get the tiny rust particles to bond together. The result? Every year at Darlington, 14,000 tons of mill scale are recovered and sold as an ingredient to the cement industry to make Portland cement.
Then there's slag. Because impurities are present in scrap steel, lime is added to the melt process. As lime melts, it rises through the molten steel collecting dirt and other impurities. After the slag is skimmed off the top, it is cooled and sent to a processor where it is put through a rock crusher and sorted according to size. Not only does crushed slag look like crushed limestone, it possesses the same physical and chemical properties as limestone. So every year at Darlington, 150,000 tons of slag is processed and recycled and sold for use in building roads and parking lots.
Useful material can also be reclaimed from electric arc furnace dust. Everyday day at Darlington, 100 tons of that dust is collected in the mill's bag house. From that dust, 20 tons of zinc can be extracted for reuse by zinc mills. Eventually that zinc finds it way into products like pharmaceuticals, paint pigments, vitamin supplements and tires.
Even the oils used in machinery and plant trucks are recycled. And because employees take pride in minimizing our environmental footprint, paper, bottles, cardboard, cans, gloves, computer equipment, printer cartridges and batteries are all recycled at Darlington.
Finally, there's water. In the water-intensive steel manufacturing process, water is used to not only cool the steel product, but the steel making equipment. To avoid discharging any of the used water into the environment, Darlington maintains its own treatment plant. To keep up with the mill's demands, that plant must collect, cool, treat and recycle approximately 35,000 gallons of water every minute. In one day, the treatment plant saves enough water to take care of the needs of a city of 500,000 people.
That's the magnitude of Nucor recycling at just one of our mills.