Calcium magnesium acetate, or CMA as it is sometimes known, is a chemical compound made by combining dolomitic lime with acetic acid. At room temperature, it is a gray to white granular powder but may be processed into pellets or flakes. It is used primarily, as an alternative to salt, as a deicing compound but has other uses as well, especially in the manufacturing industry.
This chemical is widely used as an additive to road salt or as an alternative deicer. It has several favorable characteristics which has made its use for this purpose more and more common in many areas of the world. It will melt ice at a lower temperature than standard road salt and has been shown to be effective in preventing the formation of ice down to a temperature of about -17.5 degrees F (about -27.5 degrees C). Standard road salt is only effective down to about 27 degrees F (-2 degrees C). Calcium magnesium acetate works better at preventing icing, however, than in reducing existing ice.
Its performance at low temperatures is only one reason that, in 2011, calcium magnesium acetate is becoming a preferred road deicer. It also has a slight residual effect in that it provides continued protection against icing, requiring less frequent applications after the first treatment. It is much less corrosive than salt, even when dissolved in water, and is considered about as corrosive as tap water. CMA is biodegradable, has low toxicity compared to road salt, and has been shown in several studies to be less dangerous to plants and animals. When added to salt, relatively small amounts can improve the deicing qualities over salt alone.
CMA does have drawbacks. It is more expensive than salt and is actually less effective than standard salt under certain conditions. It also tends to cake and clog spreading equipment. Studies have shown, however, that while it is more expensive than road salt by weight, it is generally more effective than salt. The savings realized from reduced wear and corrosion on roads, vehicles, and equipment, as well as reduced environmental impact, more than make up for its increased cost.
The other primary use for calcium magnesium acetate is in hydrogen sulfide removal. It is very effective in capturing this noxious gas under high temperatures. The process involves a number of chemical reactions and results in the hydrogen sulfide being broken down into calcium sulfate, an inert compound that can be disposed of. Desulfurization, as this process is known, is used in many industries but is especially important for reducing emissions of coal-burning power plants.