The Earth Story — BAUXITE: Will Climate Change Encourage Formation...

BAUXITE: Will Climate Change Encourage Formation of New Aluminum Ores?

Climate change… Take another can of brew outta the fridge, and sit back, pull off the tab, hear that satisfactory sound of escaping bubbling CO2 and… let’s see about where that can came from.

Alumina is the 3rd most common element in the earth’s crust, but is always always always found bonded with oxygen, a hard atomic bond to break. Aluminum as an elemental metal wasn’t even discovered until 1825, when Hans Christian Oersted first, with great difficulty and using a potassium-mercury amalgam, broke open that alumina-oxygen bond and reduced a lump of pure aluminum. Aluminum remained a rare curiosity of a metal, more valuable than gold, until an easier, less-expensive method of producing it from ore was developed in 1886, the Hall-Héroult process still used today. This “less-expensive” method utilizes electrolysis to remove Al from its oxide (Al2O3): in doing so, it uses 17.4 megawatt hours to produce a metric ton of metal, three times more than needed to make steel. Thus, aluminum is a recent addition in the inventory of metals commonly used by humankind.

Aluminum is produced from an ore called Bauxite: it is not a mineral, but a rock formation including aluminous oxide minerals like gibbsite, boehmite, and diaspore mixed with iron oxide minerals like hematite and goethite. It’s red, soft, heavy, generally a messy-looking rock. It can be formed from any kind of stone that is exposed to weathering on the earth’s surface. SERIOUS weathering. This kind of surficial weathering process is named “lateritic” and essentially requires a horrendous amount of rain water to percolate through a rock and leach out everything except those elements that are too difficult to leach away, leaving behind the “unleachables” including minerals with Al2O3 bonds, silica and nickel - iron oxides. It is estimated to take several hundreds of thousands of years to so totally destroy parent rocks via surficial weathering to the point that a lateritic deposit is produced.

But the kind of surficial weathering needs – a lateritic favorable environment. Which means – relatively high surface temperatures (annual average temperatures of 26 deg C) and ~10 – 11 months of constant rainfall to make 1.2 – 4 meters of rain a year! Even Brazil lags in these conditions (though lateritic soils abound there), but with increasing climate change… the conditions for laterite and bauxite formation could reach even Cretaceous conditions, once again.

Yep, take a sip from that ice cold can of beer and consider the climate that aluminum originally came from. Really makes one yearn for a cold beer…

Note: Recycling aluminum uses 5% of the electricity that is needed to produce aluminum from bauxite. Thus recycling could slow climate change, but not the consumption of beer.

Annie R

Graphic: by me using background within Vagonetto Mine of the Fokis Mine Park (Greece) and piece of bauxite (left) from near Delphi