Long before the frenzy to "go green," the ferrous and nonferrous metal industries had made significant strides in reducing greenhouse gas (GHG) emissions. The question today is how much further they can cut emissions without the benefit of a step change in production technologies.
For the past two decades, aluminum and steel producers have been aggressively reducing GHG emissions—partly as a by-product of efforts to improve energy efficiency and slice fuel consumption. Since 1990, the aluminum industry has reduced overall GHG emissions by more than 50 percent, including lowering emissions of perfluorocarbons (PFCs) by about 90 percent, according to Robert Strieter, vice president of environment, health and safety at the Aluminum Association.
Over the same period, the U.S. steel industry has sliced its energy use per ton by 33 percent in a drive that also has resulted in a sizeable reduction in GHG emissions, mostly carbon dioxide, according to Larry Kavanagh, vice president of environment and technology at the American Iron and Steel Institute (AISI). While Kavanagh couldn't quantify the GHG reduction (the industry didn't track GHG emissions back to 1990), he said that by 2008 domestic mills had brought carbon dioxide emissions down to 1.14 tons for each ton of steel produced, the lowest level of any steel industry in the world.
The U.S. magnesium industry also is seeking to reduce GHG emissions, particularly sulfur hexafluoride (SF6), which is used by magnesium producers, casters and recyclers as a cover gas to prevent molten metal from oxidizing and potentially violent burning, according to Sally Rand, program manager at the climate change division of the U.S. Environmental Protection Agency. While the industry is seeking to cease the use of SF6 by 2010, it hasn't yet settled on a substitute, she said. Possible options are HFC-134a, still a GHG but less potent than SF6, and sulfur dioxide, which isn't a GHG but is a pollutant.
Both Strieter and Kavanagh credit much of the gains in curtailing GHG emissions to advances in computing, computer controls and modeling.
"Because computers are so much more powerful, we can model the behavior of steel in a caster mold as it is solidifying and while it is being hot rolled or cold rolled," Kavanagh said. "That has given us much tighter control of our processes and product properties. This has resulted in lower consumption of raw materials, and when you need less raw materials you need less energy and you have less emissions."
For aluminum, Strieter said high-tech tools have enhanced operating controls, including increased computer control of alumina feeding into pot lines, as well as improved energy efficiency.
Both industries have been involved in a number of cooperative efforts to increase energy efficiency and cut GHG emissions, including through the EPA and the Energy Department.
The EPA has been working with the aluminum sector since 1975 to reduce PFC emissions, most recently with the Voluntary Aluminum Industrial Partnership and the Climate Vision Program, Rand said.
Pittsburgh-based Alcoa Inc. continues to work on inert anode technology, which would eliminate the PFC and much of the carbon dioxide emissions from the aluminum-making process, Strieter said. He added, however, that the technology is still in the research and development phase, with no estimates as to when it could be commercialized.
The AISI has a good relationship with the EPA but doesn't conduct joint research with the agency, Kavanagh said. It does, however, team with the Energy Department (through its Industrial Technology Program), the National Institute of Standards and Technology and universities.
Given what has been achieved in both aluminum and steel to date, there is considerable uncertainty surrounding how further major reductions in GHG emissions can be attained without a step change in technology, something both industries are actively pursuing.
Research aimed at developing an inert anode is one attempt to find such a step change, as are other current projects, including attempts to increase the efficiency of the pot by developing a continuously, or almost continuously, drainable cathode, Strieter said. "It remains to be seen how these efforts (will) pan out," he noted, adding that commercialization would likely be 20-plus years away.
The steel industry's long-term research endeavor—called the Carbon Dioxide Breakthrough Program—involves a suite of technologies aimed at changing the way steel is made, possibly without using carbon as a fuel, Kavanagh said. One project being researched at the University of Utah as part of the program proposes using hydrogen instead of carbon as a fuel. Another being conducted by the Massachusetts Institute of Technology proposes using electricity to separate iron from iron ore rather than a blast furnace. These technologies are at least 15 years away from commercialization, however.
In the meantime there may be interim steps, including certain incremental steelmaking technologies or possibly certain carbon sequestration technologies that might be adaptable to steel, Kavanagh allows. The industry has yet to find a fit among carbon sequestration technologies, he said, although it continues to evaluate available options.
Kavanagh is optimistic that a breakthrough in steelmaking will eventually occur. "The industry has already transformed itself many times. We can do it again. We are going to solve this problem because it is just the next one in the long list of challenges that we have been able to rise to."
Strieter voiced similar optimism on aluminum production technologies.