By: Larry Copeland
Local governments concerned about the environmental threat of runoff from salt widely used to clear wintry streets are turning to more nature-friendly substitutes.
Dealing with last week's blizzard across the Great Plains and Midwest, Anoka County, Minn., has been using sugarcane molasses. In Des Plaines, Ill., it's beet juice. In several places in - where else? - Wisconsin, it's cheese brine.
The alternatives don't eliminate the need for road salt but reduce the amount required. That means savings for some road agencies.
When Moe Norby, technical support manager in Polk County, Wis., first got his county of about 44,000 people to use cheese brine a few years ago, he says it netted savings of $40,000 the first year.
"We mix it with salt or salt sand," Norby says. "Dry salt will bounce (when applied). This saves 30% of salt by eliminating the bounce factor, so we can use less salt to get the same effect."
Perhaps best of all, the cheese brine - which the local F&A Dairy Products Co. uses to soak certain cheeses - is free, Norby says; the dairy previously disposed of the cheese brine in treatment plants.
Now, Milwaukee wants in. Alderman Tony Zielinski recently introduced a proposal for the city to study using cheese brine. "It's a win-win situation," he says. "Obviously, in Wisconsin, we've got a lot of cheese brine."
Tim Ridder, assistant director of public works and engineering for Des Plaines, says the city of 58,600 uses a mixture of beet juice and calcium chloride to wet streets before snow or ice strike. "When snow hits pavement, it binds to the pavement," Ridder says. "If you use salt, you're trying to break that bind. If you pre-wet, you use less salt, which is better for the environment."
Auburn Hills, Mich., a Detroit suburb, uses a mixture of 20% beet juice and 80% liquid salt brine as an "anti-icing, pre-winter storm treatment," according to director of public services Ron Melchert.
Anoka County uses a mixture of calcium chloride and sugar cane molasses, in addition to regular road salt, county engineer Doug Fischer says. The molasses helps the road salt stick and also reduces calcium chloride's corrosive qualities, he says.
State highway agencies in cold-weather climates dump about 10 million to 15 million tons of road salt every winter, according to the American Association of State Highway and Transportation Officials.
Scientists say much of it ends up in nearby streams, ponds or aquifers, sometimes even flowing into lakes and rivers.
Studies published in 2011 in the Annals of The New York Academy of Sciences and in 2010 in Environmental Science and Technology built on previous research documenting the effects of road salt runoff on water chemistry and aquatic life. The 2011 study found that "reduction in usage appears to be the only effective road-salt-runoff management strategy."
Roger Haro, biology professor at the University of Wisconsin-La Crosse, says experts once thought that salt applied to roads essentially washed into water and storm systems and dissipated with relatively little harm.
"But what we're finding out is that the salt can really build up in the shallow soil layer next to roads," he says. "You basically build up a salt bank over time.The problems associated with salt persist much longer than we originally thought."
Chronic salt concentrations can damage algae that are food sources for insects that local fish eat; in high concentrations, it can kill amphibians and plants and leach into drinking wells, Haro says.
However, Russ Alger, director of the Institute of Snow Research at Michigan Technological University, says some of the alternatives to salt there also pose environmental concerns. Beet juice, for example, may deplete oxygen in waterways.
"When you look at all the options, a lot of time road salt turns out to be pretty good," Alger says. "So we keep coming back to road salt. Cost-wise, efficiency-wise, availability-wise, it's just the best answer. I don't see it getting replaced for a long, long time, if ever."
Minnesota's Department of Transportation, which averages about 225,000 tons of salt each winter on state roads, is pioneering the use of "living snow fences" - barriers made of trees, shrubs and native grasses that can prevent snow from drifting onto roads.
But Steven Lund, the MinnDOT maintenance engineer, says, "Where we get the biggest return on efforts to protect the environment is in the training of our snow fighters."
Snow plow operators, he says, are trained "not to err on the side of over-using salt because of uncertainty."
In some places, the road salt dilemma might be moot in a few years. In separate efforts, researchers at Worcester Polytechnic Institute in Worcester, Mass., and engineers at Solar Roadways, a Sagle, Ida., company, are working to develop solar-powered systems using energy from the sun to help clear roads.
Rajib Mallick, professor of civil engineering at Worcester Polytechnic, is leading a team studying how to efficiently harvest solar energy from pavement. The harvested energy, in the form of hot liquid stored in insulated pipes or chambers, could be used to melt snow and ice and possibly to provide electricity. Mallick says such a system is possible in three to five years, most likely deployed first in large areas with less heavy traffic, such as parking lots.
Scott Brusaw, an electrical engineer and founder of Solar Roadways, is using a $750,000 research contract from the Federal Highway Administration to develop a prototype that replaces traditional asphalt with sturdy solar panels that keep the road surface just warm enough to prevent ice and snow from accumulating. The panels would also power LED lights in the roadway and provide electricity for nearby buildings.
Brusaw says there is widespread interest in the technology, and he hopes to begin manufacturing in 2014.