It may be hard to believe that any industry is beating expectations these days, but the steel industry is—at least in terms of shrinking its carbon footprint. What's more, it has had a big hand in helping customers reduce their own energy use.
Less than two decades ago, the Kyoto Protocol—which the United States has not ratified—set the then-ambitious goal of having the U.S. reduce its greenhouse gas emissions by 7 percent by 2012 from the base year of 1990.
By 2007, the latest year for which complete data is available, the American steel industry already had reduced the energy used to produce each ton of steel by a dramatic 33 percent.
Because of the close relationship between energy use and greenhouse gas emissions, the industry's aggregate carbon dioxide (CO2) emissions per ton of steel produced also have been reduced substantially. For example, in the early 1980s steelmakers in the U.S. consumed 37.8 gigajoules (GJ) of energy per ton of steel produced; by 2005, America's steel industry had lowered the average energy used to 11.5 GJ per ton. The resulting reduction of CO2 equivalents from this improvement in energy efficiency was 230,000 tonnes. The steel industry achieved this extraordinary performance with a combination of capital and material utilization improvements specifically through technological advances, which increased the use of scrap.
While the news that the domestic steel industry is the only major manufacturing sector to reduce its carbon footprint so substantially during this timeframe can come as quite a surprise to the environmental community, it can be a shock for regulators, legislators and consumers to learn that this was done at the same time that it increased production. The accomplishment is one in which the steel industry can take great pride and is evidence of why a ton of steel made in the U.S. is good for the environment, especially when compared to steel manufacturing in some other regions of the world.
However, it's important to point out that the industry didn't stop at the "water's edge" after improving its own operations. We, along with the world steel industry, have been working closely with our customers to understand how to help them achieve their "green" manufacturing goals. Often, this means looking at the entire life cycle of the material used, from when it is first produced to the end of its useful life and through its "rebirth." Steel, of course, is infinitely recyclable. Add that characteristic to the properties of the new high-performance steels and you will uncover the secret to how the industry is helping customers reduce their CO2 emissions.
Take a look at the following case studies involving bridges, automobiles and wind energy, which provide quick snapshots showing how various products utilizing steel as a dominant material are part of the environmental solution in reducing carbon footprints in today's world.
Inherently, one of the purposes of a bridge is to shorten the distance between two points. In the case of South Carolina's Arthur Ravenel Jr. Bridge, commonly known as the Cooper River Bridge, the cantilevered (cable-stay) structure reduces the commuting distance between Mount Pleasant and the Charleston Peninsula to about 7 miles from around 24 miles. In addition to shaving more than 50 percent off the 30-minute commute time without the bridge, the long-span structure also saves 167,000 tonnes of CO2 equivalents a year from the 69,200 vehicles which use the bridge daily. This has a lifetime implication of 16.7 million tonnes of savings in CO2 equivalents (based on current automotive design and assuming each vehicle meets Environmental Protection Agency standards of average gasoline consumption).
The Cooper River Bridge displaced two obsolete bridges. Due to advances in steel technology and design approaches, construction of the new eight-lane bridge used only about the same amount of steel as the two narrower bridges it replaced. Further, recycling steel from the old bridges saved 33,460 tonnes of CO2 that would have been required if the new bridge had been made completely from raw materials.
Interestingly, one of the bridge's predecessors was designed to last 50 years but, because of steel's strength and durability, it lasted 75 years. It's possible to say that as a result of this extended life, significant savings of CO2 were realized as a replacement bridge was not required for an extra 25 years.
Using 21st Century bridge-building technology and high-performance steels, the new bridge is designed to last at least 100 years—a 33-percent improvement over its predecessors, which will extend the carbon savings into the 22nd Century.
In the automotive sector, new grades of steel are helping provide significant performance advantages and lifetime emissions savings at little or no additional cost relative to using conventional steel.
The use of advanced high-strength steel (AHSS), which provides lighter optimized body designs for improved vehicle crashworthiness and improved fuel economy, can lead to a reduction of total greenhouse gas emissions (GHGs) during the complete life cycle of the vehicle. Simply put, if the body structures of all cars produced worldwide (estimated at 71 million in 2008) were made of AHSS instead of conventional steel, the emissions savings would be 156 million tonnes of CO2 equivalents.
Here's how the savings are calculated. The average weight of a typical five-passenger family car is 1,260 kilograms (2,777 pounds), with the body-in-white (BIW) structure accounting for 360 kg (794 pounds). Replacing the BIW with an optimized structure made of AHSS products creates an overall weight saving of 117 kg (258 pounds), or 9.3 percent.
Due to the BIW weight reduction, the powertrain can be down-sized, resulting in a fuel savings of 5.1 percent while still achieving vehicle performance comparable to that of the heavier, conventional steel structure vehicle. Given this fuel savings, it can be estimated that for every 1,000 kg of AHSS used in vehicles, total life cycle savings of 9 kg (20 pounds) of GHG (reported as CO2 equivalents) are achieved. This is a 5.7-percent reduction in GHG emissions over the full life cycle of the vehicle.
Furthermore, the weight reduction means less steel is required for each vehicle, resulting in a lifetime saving of 2.2 tonnes of CO2 equivalents per vehicle. These savings more than offset the total CO2 emitted during steel manufacturing for all the steel used in the vehicle.
Electricity produced by wind turbines is generated with significantly lower lifetime CO2 emissions than the global average for electricity production by other means. Many predict that the twin pressures of meeting energy demands while mitigating its effect on climate change will result in a rapid increase in wind power capacity.
Steel plays a vital role in wind power generation. Currently, the world wind energy sector consumes approximately 1.5 million tonnes of steel a year. About 85 percent of the wind turbine towers around the world are installed on tubular steel structures. The choice of steel offers the advantages of strength, durability and mobility as the towers can be manufactured in sections up to 100 feet and then fitted together and installed on site.
A wind farm by itself, of course, emits no CO2. What's notable is that energy used to build, operate and dismantle a typical turbine is recovered within nine months of operation. That's just the start of the savings. Looking at the case of the Horns Rev wind farm off the coast of Denmark, its 80 wind turbines produce an estimated 650 gigawatt-hours (GWh) a year, generating almost 13,000 GWh over its 20-year lifetime. When the turbines reach the end of their life, recycling 90 percent of the steel from the Horns Rev wind farm will save 47,000 tonnes of CO2 in primary steel production.
Globally, at least 90 percent of the steel from wind turbines can be recovered for recycling (including steel foundations). Without the recycling scenario, the environmental impacts of a wind turbine production phase would be significantly higher, highlighting the importance of using and recycling steel. For example, increasing recovery to 96 percent from 90 percent would result in reducing greenhouse gas emissions by approximately 3 percent based on life-cycle assessment studies.
The numbers discussed here also apply to the first urban wind farm in the U.S., the 445-square-meter (4,800-square-foot) Steel Winds' site in New York state donated by ArcelorMittal SA, which generates more than 50 GWh of electricity a year, powering about 6,000 homes and saving 25,000 tonnes of CO2 a year.
Steel as a solution
As part of an ongoing effort, additional environmental case studies are being developed showing similar positive examples in food cans, automobile fuel tanks, passenger rail and buildings. The goal is to give our customers the information they need to address carbon footprint questions. The answers include a life-cycle approach, including manufacturing, use and reuse.
In all cases, we want our customers to know they have made the correct material selection decision by using the EnviroMetal steel. BILL HEENAN
Bill Heenan is president of the Steel Recycling Institute, Pittsburgh. Metals Forum welcomes submissions addressing issues of interest to the metals community.