&#62; However turning the entire freight industry from Steel to Aluminium containers would probably require depleting all the earths aluminium reserves, and then likely require discovering an extra-terrestrial source and probably depleting that too.<p>The 8 most common elements in Earth’s crust (by mass):<p><pre><code>  * 46.6% Oxygen (O)
  * 27.7% Silicon (Si)
  * 8.1% Aluminum (Al)
  * 5.0% Iron (Fe)
  * 3.6% Calcium (Ca)
  * 2.8% Sodium (Na)
  * 2.6% Potassium (K)
  * 2.1% Magnesium (Mg)
</code></pre>
(from <a href="http://www.windows.ucar.edu/tour/link=/earth/geology/crust_elements.html" rel="nofollow">http://www.windows.ucar.edu/tour/link=/earth/geology/crust_e...</a>)