After a destructive weekend, all the snow from Winter Storm Jonas is now plowed to the periphery of streets across the Eastern seaboard. The accumulation snarled traffic from Washington, DC to Boston---but all that could have been a lot worse if not for the small armies of salt trucks glazing the roads with brine in advance of the storm.
If you live in a northerly spot, those plows and salt trucks are familiar. But snow removal has actually undergone something of a renaissance in the past decade---and the future is brine. Applied before the first patina of flakes, a mixture of salt, water, and chemical agents keeps snow from sticking to the road. Some of the best brines, it turns out, are made from byproducts left over from industrial food processes.
Washington DC uses beet juice. So does New Jersey. In the past, the Garden State also used pickle juice. Argentina uses wine byproducts. And when the meteorologist predicts snow in Wisconsin, Polk County sprays the roads with cheese brine. "The dairy gives us that for free, and we will go through 30,000 to 65,000 gallons a year," says Moe Norby, technical support director for Polk County's highway department. The best water comes from provolone, because it has high salt content. Mixed with chemical additives, the cheese brine goes down before the storm and keeps the snow from freezing to the road. The arrangement is win-win. The dairy gets free waste processing, and the county gets a cheap spray that keeps its roads ice-free down to -23˚F.
But not every snow-laden county has a local cheese factory. "Really when you start getting into how you treat road surfaces, the major cost is transportation. Getting whatever you are going to use to you," says Bret Hodne, public works director for West Des Moines, Iowa. In the 1990s, Hodne was one of the salt brine pioneers.
Hodne and a few other public works managers around the Midwest started mixing salt and water together to kickstart the melting process. Salt lowers the freezing temperature of ice, but it has to be wet for the chemical reaction to take place. Putting dry salt down---which remains the practice in many places---means you have to wait for a little bit of premelting. "Now we had a tool to use ahead of an event to prevent snow and ice from bonding to the pavement, so it was easier to plow," he says. "That changed the way the industry was looking at how to handle winter events."
He and other amateur winter chemists tried out all sorts of new concoctions. Calcium chloride was one of the first additives. "It's hydroscopic, and has been used for a long time to control dust on country roads," says Hodne. That hydroscopic property help the salt brine last longer. They moved on to other chemicals that do the same general job, but pose less environmental damage. During a storm, Hodne and his drivers use sensors to measure pavement temperature, surface friction, and other properties to calibrate their brining and plowing.
"The first time I saw any type of food byproduct in a brine was at an American Snow Conference in 1996," says Hodne. He initially thought it was crazy, but eventually realized that northern Europeans had been using syrups and molasses for years. Unlike the brines that marinate US roads, the Swedes, Norgwegians, and Germans grind sugar beets into dry rubs.
Food byproducts serve multiple roles in the brine. Not all of them have inherent salt content, like Wisconsin's provolone bath. Some of them are sugar-heavy, like the molasses-enhanced brine the Massachussetts county of Lexington used to prep its roads for Winter Storm Jonas. "What you do is spray it directly on the roads, and the water evaporates and you're left with the salt solid, magnesium, and molasses," says public works superintendent Marc Valenti. The sugars in the molassses lower the freezing temperature, and they also help the salt and magnesium stick to the road.
And there's no perfect mixture. "Whenever you look at putting a liquid product on the road, you have to know how the storm is going to come in," says Hodne. If the forecast calls for rain before snow, there's no use in brining at all. If the storm is cold, but not too cold, Hodne says he opts for straight up salt and water, no sugars or additives necessary, because the snow isn't likely to stick to the roads anyway. Colder, icier conditions call for food and chemical additives.
Which seems like a lot of work when much of the country sits right alongside what appears to be a huge, natural source of brine: the ocean. So why don't cities like Boston, Baltimore, and New York just pump the stuff straight through hydrants? Salt content in the ocean isn't the optimum, and if public works puts it down prior to a storm, it could actually cause advance freezing. "The optimum brine for treating roadways is about 23.31 percent salt," says Valenti. Ocean water is about 3.5 percent salt. And I'm pretty sure it's around 5 percent sharks, and nobody wants to deal with sharks and big piles of melting snow.
1UPDATE: Correction 1/27/16 1:36 PM ET Original stated as 23.5 percent. Too much salt content makes the brine less effective at de-icing.
