Concrete often gets a bad rap for its emission of seven percent of the world's CO2, but steel is no better, with an equivalent output. The steel sector is also the second-largest industrial consumer of energy, despite gains made in recycling, which reduces the embodied energy of the material (steel is the most widely-recycled material on the planet, and 42 percent of "new" crude steel is recycled content).
Scientists at the University of Utah are keen on finding ways to improve the environmental track record of the steel sector. This is a particularly difficult challenge, given that steel production is considered to be approaching the physical and chemical limits of resource efficiency. However, the Utah researchers have developed a new flash-forming technique of creating iron, which was published in Steel Research International, offers significant benefits.
A typical way to create iron is using a blast furnace, which is filled with iron ore, limestone, and coke (high-carbon fuel made from coal). The iron is smelted from these ingredients with the introduction of large quantities of heat and forced air, resulting in the formation of liquid iron underneath a layer of slag. Cast iron has an embodied energy of 16-20 MJ/kg and a CO2 footprint of 1.4-1.6 kg/kg.
The new flash ironmaking process avoids the use of coke, and instead directly reduces iron ore particles using hydrogen or natural gas. This method would allow steel producers to bypass the blast furnace altogether, and at the same time employ a more seamless steel-making process than the one used today. The novel approach suggests that manufacturing still has plenty of room for environmental improvement, even with the oldest and most common of industrial materials.
Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.