Sustainability Highlights


Making Steel With Less Energy

In 2002, Nucor’s first Castrip micro mill in Crawfordsville, Indiana went on line. In 2009, we expanded the use of this technology by building a second Castrip plant in Blytheville, Arkansas. With these two Castrip plants, Nucor continues to improve its position as the nation’s largest recycler.

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Castrip Factoids

The Castrip process transforms molten steel into steel sheets instantly, producing Ultra-Thin Cast Steel (UCS). Castrip is the first flat-rolled product to be direct-cast into sheets as thin as 1.4 mm and simultaneously rolled at an incredible 0.7 MM. In short, we can deliver a hot-rolled product at cold-rolled gauges.

This single-step process dramatically reduces the time, space, energy, and manpower needed to produce each coil. Each micro mill consumes 84% less energy than a conventional mill, with a 75% reduction in greenhouse gas emissions. In 2014, Castrip coils contained an amazing average of 94% recycled content.

High-strength, low-alloy, high-carbon, and weathering steels are now part of Castrip’s product offerings. The steel grades that we can produce using Castrip continues to expand.

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Not Much Left For The Landfill

Not many people realize how many products are generated from Nucor’s steel-making process. Take a look at the products generated by the steel mill located in Darlington, South Carolina, which is a typical mini mill that produces about one million tons of steel a year.

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Co-Product Factoids

First, there is mill scale, or iron oxide. Every year 14,000 tons of mill scale are recovered and sold to the cement industry as an ingredient in Portland cement. Then there’s slag. After slag is skimmed off the steel bath during the melt process, it is cooled, crushed, and sorted by size—ending up very much like limestone. Every year at Darlington, 150,000 tons of slag product is processed and sold for use in building rods and parking lots.

Electric arc furnace dust can also be reclaimed. Every day 100 tons of dust is collected in the mill’s bag house. From that, 20 tons of zinc can be extracted for reuse by zinc mills. It eventually finds its way into products like pharmaceuticals, paint pigments, and tires.

Finally, there’s water. In the steel-making process, water is used to cool both the steel product and the steel making equipment. To avoid discharging the used water into the environment, the mill maintains its own treatment plant, which collects, cools, treats, and recycles about 35,000 gallons of water every minute. Recycling of this water saves enough to meet the needs of a city of 500,000. This is the story of just one of our mills.

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Reducing Our Idle Time

Many of our facilities use powerful diesel locomotives to transport rail cars full of scrap metal from the yards to the melt shops. When not in use, these engines have typically been left to idle rather than let the engine completely cool down.

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Our innovative teammates determined we could cut back on emissions, energy, and diesel fuel consumption by reducing the idle time of the locomotives while keeping them warm and ready to go. This was done at several Nucor facilities by installing SmartStart Systems from ZTR Control Systems on their locomotives. These systems reduce idle time by automatically shutting off and starting up the engine.

SmartStart works by shutting off the engines after ten minutes of idle time and automatically restarts the engine if its temperature drops below 125 degrees Fahrenheit, if the air pressure drops, if the ambient temperature drops, or if the battery voltage gets low. This is necessary because most engine wear occurs between the time the engine starts and the time it warms up. By keeping the engine oil just warm enough to prevent cold starts, we can extend the life of our locomotive engines while reducing their environmental footprint from unnecessary idling.

100,000 gallons of fuel saved yearly by reducing locomotive idle time

Nucor has installed SmartStart kits on a total of 13 locomotives since the program began in 2008. Each year, we save approximately 100,000 gallons of diesel that would have been used for idling locomotives. This not only reduces fuel consumption, but leads to a significant reduction in the associated emissions. It’s just one more way we’re looking to reduce our environmental footprint.

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Mini Mills

Consuming Fewer Resources, Releasing Fewer Emissions

As the name implies, Nucor mini mills are small. Their small environmental footprint is just one of the many benefits. For starters, a mini mill’s Electric Arc Furnace (EAF) consumes less natural resources than the traditional blast furnace. In fact, every ton of steel made by mini mills eliminates the need for the following:

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  • 2,500 pounds of iron ore
  • 1,400 pounds of coal
  • 120 pounds of limestone
  • 1,705 kilowatt hours of electricity

To put this in perspective, the 22 million tons of steel Nucor made in 2007 saved enough electricity to power more than 6.5 million homes for one year.

While this conservation of natural resources is impressive, it pales in comparison to the benefit of reducing criteria pollutants released into the atmosphere. Compared to the blast furnace, a mini mill’s EAF releases 94 percent fewer pounds of pollutants into the air per ton of steel made.

It’s a win-win situation, and it all starts with recycling. By cleaning up our land of scrap steel, we’re able to reduce mining waste by 97%, air pollution by 86%, and water pollution by 76%.

Criteria Pollutants

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Scrap Recycling

Where have all the Junkyards Gone?

Forty years ago, our country’s landscape was littered with junkyards—expansive lots piled with rusting heaps of demolished cars and broken down appliances. It was not a pretty sight.

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Nucor EAF method typically allows for 89.5% total recycled content

Then the Electric Arc Furnace (EAF) was born. It was based on a simple concept: use scrap metal as feedstock and melt it with electrical energy. While the initial motivation was purely economic, the result was a huge benefit to the environment.

At first, EAF powered mini mills were small operations producing basic materials like rebar. Nucor’s culture of continuous improvement drives us to find ways to produce higher quality products. These efforts are pushing us further and further into the markets previously dominated by integrated steel mills.

Best of all, on average, 64% of all steel is now recycled and kept out of landfills. So a car in this decade may turn into soup cans in the next decade and an appliance in the decade after that.

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Slag Refining

A New Generation Of Slag Products

Nucor is leading the way in developing a new generation of slag products. Slag is created as a layer of insulation on top of the steel bath during the scrap steel recycling process. This layer not only lowers energy costs per ton and reduces CO2 emissions, it removes impurities from the molten steel.

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Slag is skimmed off the top of the bath, cooled, crushed, and sorted according to size, creating a variety of aggregate products. Crushed slag looks similar to crushed limestone and possesses many of the same physical and chemical properties.

Slag can be used as aggregate in concrete, as well as used in roads as skid resistant material.

Slag is an environmentally responsible choice. For every ton of slag used, one less ton of gravel will have to be dug out of quarries. It is also effective at filtering pollutants from storm water runoff such as agricultural, urban, and industrial.

Nucor has been working with the National Slag Association to develop standards for various types of slag products. By setting these standards, we are creating a more refined product for end users and educating them about the environmental benefits of slag.

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