De-icing Salt Damages Roads, Lakes, and Rivers

Dr. Mingruo Guo has been working with dairy products since 1982, when he started pursuing his PhD in dairy science chemistry. Since 2002, Guo has been working on a project to synthesize an environmentally safe de-icer for roads from whey, a dairy byproduct.Each year, approximately 90 billion pounds of whey byproduct is produced in the dairy industry. Of these 90 billion pounds, about 40% is not used, and must be dumped into bodies of water.When the whey interacts with the water, the organic compounds in whey are oxygenated, taking oxygen out of the water supply and decreasing the capacity of the water to support marine organisms. Furthermore, whey contains the elements nitrogen and phosphorus, which can also pollute water.Dr. Guo’s attempts to utilize this excess whey not only help to decrease the amount dumped into bodies of water, but they aim to create a de-icer for roads and sidewalks which is not harmful. The problem with the current de-icers utilized by states like Vermont, according to Guo, is that the chlorine in the salt (NaCl) can damage the surface of the roads, and can have adverse effects on bodies of water.Chlorine acts as a rusting agent and affects the metal rods, which are an integral part of roadways. Once the metal beneath the surface of the roads begins to rust, the concrete or asphalt begins to expand, creating cracks in the road.Certain cities around the Great Lakes have begun to minimize the salting of their roads to combat potential salt pollution. Dr. Guo’s solution to both of these problems is to create an environmentally friendly salt, sans chlorine.Guo’s lab has successfully converted whey into a salt (potassium acetate), which has little to no detrimental effects on the environment. The problem currently facing Guo is yielding enough product to make the process affordable – currently, Guo’s team experiences an average of 7% or 8% yield, meaning that for every 100 grams of whey used, only 7 or 8 grams of de-icer is produced. The problem is due to a catch-22 in the conversion process. The bacteria being used for the fermentation process, which convert the whey into potassium acetate, are sensitive to both pH and salt content. Unmodified, the pH of the whey is too low for the bacteria to function, but raising the pH would require also raising the salt content to a concentration at which the bacteria also cannot function. Dr. Guo is currently trying to overcome this problem.Guo stresses that this is no small problem- in 1991, the Transportation Research Board estimated that the government spends between $3.5 and $7 billion dollars each year to repair roads that have been damaged by salt. In 2004, Vermont dumped more than 108,000 tons of salt onto its roads, according to the Vermont Agency of Transportation. Dr. Guo and others like him are beginning to advocate a low-salt diet for our nation’s roads.