A second benefit of bentonite is its environmental friendliness, Bergeson says. Iowans are increasingly concerned about possible environmental damage associated with chemical dust control materials such as calcium chloride. Bergeson says that bentonite is a naturally occurring mineral containing no salt and poses no danger to the environment. And it does not contribute to vehicle rusting, as calcium chloride does. In addition, bentonite is more cost effective than other dust control materials.
Researchers estimate the cost of bentonite treatment at half the cost of calcium chloride treatment.
Not only are initial application costs lower, but bentonite has a much longer effectiveness period, reducing costs even more. Because bentonite's bonding properties survive alternating wet and dry periods and even Iowa's long winter freeze, its term of effectiveness is not months but years. These results compare very favorably to the normal three-month total period of effectiveness for calcium chloride. Bergeson says that, depending on the desired amount of dust control, maintenance supervisors may want to apply bentonite to limestone roads every two to three years. Bergeson's research also addresses possible problems associated with using bentonite as a dust control measure.