Dust suppressants are commonly used within Canada and the U.S. to control dust emission, corrosion, and to reduce airborne particulate matter. They control erosion and road maintenance costs, and aid in abating dust that reduces visibility, environmental safety and health. Dust suppressants work by changing the physical properties of the soil surface.
Calcium chloride is an environmentally safe product used for dust abatement. It is naturally mined and is effective in limiting dust on roadways. Compared with other substances used in dust control, calcium chloride is not only environmentally friendly, but is economical and effective.
Although there is no environmental impact in using water as a dust suppressant, research shows water will only control dust for up to 12 hours due to its evaporation rate. This results in greater operating costs. Calcium chloride, in contrast, lasts longer than water because it doesn’t evaporate; rather it is hydroscopic, drawing in moisture and retaining it. Calcium chloride is environmentally safe as well, due to its low corrosion rate.
Magnesium chloride, like calcium chloride, is a water-absorbing chemical. In higher concentrations, magnesium chloride can be very corrosive to steel, may become slippery when wet, and rainwater tends to leach out highly soluble chlorides. During humid weather, magnesium chloride is seen to work less effectively than calcium chloride.
Lignin sulfonate is a byproduct of paper mills. Although it can be less expensive than calcium chloride in some areas, it lasts for a fraction of the time. The effectiveness of lignin sulfonate products is reduced or completely destroyed in the presence of heavy rain because of its solubility in water. Therefore with rain, frequent re-application will be required, costing more for re-application and maintenance. In addition, it has been found that higher levels of lignin sulfonate can cause high coloring effects in water bodies, reduced biological activity, and hindered growth in fish. Lignin sulfonate is also slow to biodegrade, so may contribute to de-oxygenation of surface water. This may cause a roadway to become slippery when wet.
Cut crude, oil emulsions, and organic petroleum products can all be used for dust control. In Alberta, 10% of all recycled oil is used on roadways for dust control (provided it meets provincial guidelines). This practice raises many environmental concerns that stem from the heavy metal content and the chemical characteristics of the oil deposit from which the petroleum product originates. Several studies have shown that waste oils may contain known toxic and carcinogenic compounds. Used oils and solvents may have even higher toxic concentrations. Potential environmental impacts are highest from organic petroleum products.
The cost for road maintenance from putting oils on the road can increase significantly, compared to using calcium chloride. At Tiger Calcium, we ask clients to reactivate their calcium by watering the road and re-grading it; a minimal cost to the client. Since petroleum-based products form a crust with adequate thickness by agglomerating the soil particles, this reduces the amount of immediate maintenance that is required on unpaved roads. In the long term, however, when failures such as potholes occur, there is no way to repair them using normal low cost techniques, such as grading. Unless these roads are milled to return them to unsealed status, the structural failures get paved over, again setting in motion the long-term maintenance and environmental costs.
Currently, Ontario has prohibited only one dust suppressant, namely used oil, and Quebec has banned used oil for use as a dust suppressant in that province.