Baby Boomers and fans of vintage radio/TV/movies may recall The Lone Ranger. The main character was a masked cowboy who fought injustices in the Old West with a 6-gun loaded with silver bullets. Fast forward to 2006, and the ranger might be packing green bullets.
Philip G. Malone’s presentation at the green chemistry conference described how an environmentally friendly bullet certainly is needed. Malone, who is with the U. S. Army Engineer Research and Development Center in Vicksburg, Miss., said the need exists at small arms firing ranges, where military personnel, law enforcement people, sports enthusiasts, and others fire at targets. There are more than 10,800 of these ranges in the United States. As the bullets zip, they deposit in the surrounding soil an amazing 80,000 tons of lead every year.
Range owners are environmentally aware, periodically "mine" the range and try to recover as many spent bullets as possible in order to control soil and ground water pollution. Some even resort to cleaning lead from the soil and dust, a process that can cost up to $500 per cubic yard. However, corrosion of lead fragments left in soil does result in lead compounds moving into the environment.
Malone reported on a green alternative − a zinc-lead composite bullet that uses zinc as a sacrificial metal to protect the lead in the bullet.
The zinc has much the same effect on lead as it does when used to galvanize iron (with zinc corroding and the iron being protected). Malone and colleagues compared pure lead bullet slugs and green slugs in a standard acetic acid leaching test. Pure lead slugs leached more than 14 parts per million (ppm) lead, compared to less than 0.2 ppm for the zinc-plated lead composite slugs. The green bullet would have a density − an important consideration in performance − only 5.5 percent less than a conventional bullet. Malone said that substituting a lead-zinc composite for lead in bullets would be an economical and environmentally beneficial move.
A U. S. Army representative in the audience emphasized that galvanized lead is among several alternatives being considered for implementation.