One way to attempt to define any word is to think about its opposite. In that vein, the situation concerning our helium supply may well be the absolutely least sustainable element of our entire industrial system. I won't get into the details about the Helium Stewardship Act of 2012 (details here, and here), but let's just say the situation is so bad that Republicans and Democrats are agreeing. So what is the problem? It is not just the mismanagement of our helium reserves - the largest in the world -which the HSA is attempting to address. Rather, it is the twin facts that there just isn't very much helium on earth, and that if we loose it, we lose it - forever.
Helium is unique among all elements in the fact that is both very light and inert. Hydrogen is even lighter, but highly reactive, which means that is generally found bound to heavier elements such as oxygen, forming water. Helium, however, floats around all by itself. Now if you remember your freshman chemistry course, you may recall that kinetic energy is proportional to 0.5 x mass x velocity squared. You may also remember that temperature is basically nothing more than average kinetic energy. This implies that at any given temperature, small things must be moving faster. Well, helium is so small that its velocity at the temperatures found in the upper atmosphere (where it inevitably floats, being lighter than normal air) is so high that it often exceeds the escape velocity of the earth. So if you pop that balloon, your helium floats up and up, and doesn't stop until it leaves the earth's grasp forever.
For this reason, helium only exists as a trace as in the atmosphere (roughly 5 parts per million), making it all but impossible to extract from air. Rather, our helium sources here in earth are natural gas wells. Helium is naturally formed as the by-product of some nuclear decay processes. In a few special locations deep beneath the earth, a combination of high concentrations of radioactive elements and impermeable cap-rock has allowed small pools of helium to accumulate over millions of years, trapped beneath the earth. This virtually always are co-located with natural gas, which is trapped under the same rock layers. Our National Helium Reserve in Texas, whose contents we have been selling off at below-market rates for years, contains 30% of the world's known helium reserves...and will be gone by 2018. Experts estimate that there are only 25-30 year's worth of extractable helium left on earth.
With respect to all other elements, the worst we can say is that we are trashing our high quality ores and resources, and our kids and grandkids will be forced to go through a time and labor-intensive process of picking those valuable atoms out of our trash, or extracting them at great effort from whatever low-quality resources we may have overlooked. Not so with helium. If we don't catch it and recycle it, it is gone. Our descendants will be forced to either do without, or harvest it from space at an astronomical cost. Lest you think helium is just for balloons and blimps, it is also critical for any number of industrial and technological processes, such as MRI scanners. All sorts of our latest and greatest inventions either cannot work or cannot be manufactured without it. The Helium Stewardship Act is a step in the right direction, or at least a cessation of the outright stupidity of heading in the wrong direction, but we need to act far beyond what is in this bill. Helium use should be restricted to only the highest value applications immediately, and the reserves protected rather than sold. Likewise, helium recycling should be enforced. This resource, more than any other, is one that we need to protect.