C & E's Constructive Blogs: Some Considerations of Sustainability...

... in Steel Frame

Manufacture

The raw materials for steel are iron ore, coal, limestone, air, and water. The ore, coal, and limestone are minerals whose mining and quarrying cause disruption of land and loss of wildlife habitat, often coupled with pollution of streams and rivers. Coal, limestone, and low-grade iron ore are plentiful, but high-grade iron ore has been depleted in many areas of the earth.
Supplies of some alloying metals, such as manganese, chromium, and nickel, are becoming depleted.
The manufacture of a ton of steel from iron ore by the basic oxygen process consumes 3170 pounds of ore, 300 pounds of limestone, 900 pounds of coke (made from coal), 80 pounds of oxygen, and 2575 pounds of air. In the process, 4550 pounds of gaseous emissions are given off, and 600 pounds of slag and 50 pounds of dust are generated. Further emissions emanate from the process of converting coal to coke.
The steel industry has worked hard to reduce pollution of air, water, and soil, but much work remains to be done.
The embodied energy of steel produced from ore is about 19,200 BTU/pound.
Most structural steel in North America is made from recycled scrap; its embodied energy is only about 39 percent of that of steel made from ore.
Sixty-six percent of all steel in eventually recycled, which is a very high rate. In a recent 10-year period, 1.2 trillion tons of steel were recycled worldwide.

Construction

Steel fabrication and erection are relatively clean, efficient processes, although the paints and oils used on steel members can cause air pollution.
Steel frames are light in weight as compared to concrete and masonry frames that would do the same job. This means that a steel building generally has smaller foundations and requires less excavation work.
Some spray-on fireproofing materials can pollute the air with stray fibers.

In Service

Steel framing, if protected from water and fire, will last for many generations with little or no maintenance.
Steel exposed to weather needs to be repainted periodically unless it is galvanized or given a long-lasting polymer coating.
Steel framing members in building walls and roofs should be thermally broken or insulated in such a way that they do not conduct heat between indoors and outdoors.
When a steel building frame is demolished, its material is almost always recycled.
Steel seldom causes indoor air quality problems, although surface oils and protective coating sometimes outgas and cause occupant discomfort.