Q: What are environmental pros and cons to using aluminum as a building material?
When evaluating eco-friendliness of building materials the following questions need to be asked: Is the material toxic? Where does it come from? Is it recycled? How intensive is the manufacture? And is it reusable & recyclable?
Aluminum is fabricated from bauxite, a mineral found primarily in tropical areas. More than 160 million tons of bauxite are mined every year. On average, 4-5 tons of bauxite are needed to produce one ton of aluminum. The major locations of mines are found in tropic and sub-tropic areas. Bauxite is currently being extracted in Australia, Jamaica, Brazil, Surinam, Venezuela, Guyana, Guinea, India, China, Russia, Kazakhstan and Greece. A considerable factor in the cutting of tropical rainforests originates from the aspiration to get entrance to bauxite mines.
The mining processes are typically associated with several environmental problems such as deforestation, habitat destruction, soil erosion, disturbance of aquatic and terrestrial biodiversity and pollutant runoff. Depending on a location of the mine, the transport of the material can cause additional environmental problems including air pollution with GHG (green house gas) emissions. The processes of ore refinement in general produce heat, GHG emissions, combustion emissions, using up a considerable quantities of water. The water use is particularly remarkable problem associated with the aluminum manufacture. Being extremely water-intensive, the manufacture generates wastewater contaminants such as fluoride, aluminum, antimony, cyanide and nickel.
Most aluminum building products contain virgin aluminum, while about 1/3 of the aluminum used in the US comes from recycled materials. The good news is that aluminum is recycled from post-industrial sources including stamping offal & head, butt & edge trim from rolling or operations of extrusion. Aluminum is also recycled from post-consumer sources including soda cans, end-of-life building products and scrapped automobiles. Overall, post-consumer sources contribute to about 40% of the recycled aluminum. It is good to know that mass-produced aluminum is a young building material. Since aluminum building components have long life, aluminum is only starting to be recycled from constructions.
The benefits from using recycled aluminum are many. Aluminum produced from recycled materials requires only 5% of the energy and GHG emissions required to produce aluminum from bauxite. Furthermore, 4 tons of bauxite are saved for every ton of recycled aluminum. Another plus from using recycled aluminum instead of raw materials is that it reduces the air pollution by 95% of SOx and NOx, while water pollution is reduced by 97%.
As for toxicity, aluminum is considered inert. Less VOCs are emitted from in situ factory applied finishes than field applied coatings. Apparently, the primary out-gassing happens at the plant under controlled conditions. Aluminum is prone to corrosion and therefore it must have a protective coating such as anodized or duranodic finish.
To conclude, there are different shades of green in case of aluminum. The pros is that it can be recycled and reused. Also, the aluminum is non-toxic. The cons is that its ore is extracted in mines that are often far from the place of the intended use of aluminum. Furthermore, its extraction and manufacture involve energy and water intensive processes that cause habitat degradation and pollution.
Ouboter, P. Environmental Issues Related to Bauxite Mining