US Army developing eco-friendly smoke grenades

The US Army is working on next generation eco-friendly smoke grenades to provide cover for its troops in the battle field.
The new grenades are being tested as a replacement for current smoke grenades, based on Second World War technology, that are used by US troops to mask themselves from enemy fire.
The US Army Edgewood Chemical Biological Centre (ECBC) is working on a new formula to replace the 70-year-old HC Screening Smoke Grenade.
Four basic smoke compositions are being considered.
First is a zinc-free composition, HX, similar to the hexachloroethane composition, but one that does not produce a toxic, irritant smoke containing zinc chloride.

The metals other than zinc produce smoke as dense as the HC, but without high amounts of acidity.

The second composition is hexachloroethane-free.
"The advantage of this composition is that none of the ingredients are water soluble, and that nearly eliminates the contamination of water supplies," said Joseph A Domanico, senior engineer for the Pyrotechnics and Explosives Branch.
By encapsulating chlorine atoms in a plastic matrix, the potential for ground water contamination is nearly eliminated.
The chlorine in the matrix is freed by the heat of combustion, allowing the smoke to pull water from the atmosphere and producing a dense smoke cloud.

Because the rest of the plastic matrix is carbon, the smoke is filled with fine carbon particles giving a dark grey to black colour.
The third candidate contains a solid solution of magnesium and aluminium, and produces a large quantity of metal oxides as its main smoke component. Basically, the smoke comes from the burning of the combination of metal powders.
This smoke is bright white and easily blends in a bowl with a binder, or in any other suitable mixing system.
Using a binder similar to "Super Glue," the composition can be used in grenades, short range mortars and even in long-range artillery, allowing forces to be great distances from their targets.

The Lithium-Plus composition is the fourth smoke candidate. It is based on lithium combustion technology.
A chemical reaction uses a lithium salt to produce a superior smoke cloud, pulling large quantities of water from the atmosphere. Lithium salts are efficient, and result in a dense, bright white smoke cloud.
The compositions will be tested and evaluated in combat conditions, from cold to hot environments; in forest, desert and urban terrains; and whether or not friendly troops and civilians are in the combat zone.