By Katie Stannard
Snow + cold + ice + Michigan = challenging walking and driving. But did you know that legislation now requires the Michigan Department of Transportation (MDOT) to test beet juice and other agricultural products as road deicing components? Say what?
A detour into science will aid in our understanding. The basic idea is that salt lowers the freezing/melting point of water. The molecules found in salt solutions or brines applied on roads as pre-wetting or deicing agents interfere with the regular development of lattice-like ice crystals in water. They intersperse between water molecules, impeding crystal formation.
Do you remember learning in physics that everything is moving toward greatest entropy? This example from a physics department blog at the University of Illinois Urbana-Champaign illustrates the point: “Say you have a cup of pure water and a cup of somewhat salty water. As you lower the temperature some of the pure water starts to form ice crystals. The reason is that although the frozen water molecules, lined up into a crystal, have fewer ways to move around (lower “entropy”) than the liquid molecules, they release heat when they freeze and that raises the entropy of the surroundings even more. So the net entropy goes up as the water freezes, as it always does on the way to any equilibrium state.
What about in the salty water? There’s one extra term in the entropy change. The salt doesn’t fit into the ice crystals. So as they form, the remaining salt is left with less room to roam around in, and thus less entropy. So you have to get the salt water even colder before you get a net entropy gain from freezing it. It sounds like that explanation isn’t special to salt–it should work for any molecules or ions dissolved in the water. And so it does.”
MDOT and its contractor crews use various methods to treat roads during the winter, including calcium chloride, brine, sand, and beet juice currently when salt is ineffective, according to spokesperson Aaron Jenkins. He noted that it’s a balance between keeping roads clear and making the most of the maintenance budget.
Rock salt works decently well down to 15℉, but loses its effectiveness in colder temperatures. For current trials in conjunction with Montcalm County, MDOT will test beet juice in combination with salt and salt solutions on 24 lane miles to help with removal of hard-packed snow or ice, for temps between 0 and 15℉. The solution enables deicing at those lower temps, plus helps salt and brine adhere better, longer.
The effective element in beet brine is derived from sugar beet molasses, a waste byproduct of the refining and fermentation process that produces table sugar crystals. It’s the sugar in the commercially prepared beet and salt solution which lowers the freezing point of the ice, binding to the salt, creating a slightly gooey concoction.
As the fourth largest producer of sugar beets in the U.S., utilizing beet byproducts is economically significant for Michigan’s beet farmers. They say they could grow enough sugar beets to coat all roads in Michigan, Ohio, and Indiana!
Growing in the thumb and Saginaw Valley areas, 900 Michigan sugar beet farmers plant 160,000 acres in 20 counties, producing 1.1 billion pounds of sugar. Cost estimates for a gallon mixture of 20% beet juice and 80% salt brine were $1.70-$1.85 in 2019. A mature sugar beet has white flesh, is 1 foot long, weighs 2-5 pounds, and contains 18% sucrose, concentrated in its taproot. Fun fact: the ratio for how many pounds of beets it takes to make a pound of sugar is roughly 18:1. Sugar beets account for roughly 57% of domestic sugar.
How have other states fared in using beet brine? The Missouri Department of Transportation uses beet and salt brine to about 5℉. Colorado tested beet brine solutions with similarly positive results. But their research showed that phosphates from agricultural byproducts such as beet brine caused higher levels of phosphate runoff, which acts like fertilizers, promoting algal growth. In waterways, excess algae growth can consume oxygen needed by fish. Colorado DOT noted that its shallower waterways would likely enable greater algal growth, as compared to Missouri’s deeper waterways.
According to Sciencedaily.com, a 2018 research study into the physiological impacts of beet juice deicers revealed problems in mayfly nymphs, considered an indicator species because of their sensitivity to runoff contaminants. Results showed higher blood salt levels and fluid retention, among others. Investigators concluded that more research would be necessary to assess effects on ecosystems.
MDOT’s tests will include environmental impacts, as the beet juice trials continue next winter in two additional regions. Evaluations will focus on effectiveness and cost effectiveness of beet brine and other agricultural by-products. A report will be due in June 2025 from MDOT to the transportation committees of the House and Senate. That report will help to determine whether there would then be an authorization to utilize the beet juice mixture statewide.
Are locally-sourced brines being used in other states? Pickle brine was trialed in New Jersey and is effective to -6℉. In Wisconsin, cheese brine–a leftover from the production of soft cheeses like mozzarella–has been tested, and found useful down to -21℉.
For temperatures below 0℉ in Michigan, sand might be utilized, but MDOT’s Jenkins says its use is mostly limited to rural areas. Though great for improving traction, more environmentally friendly, and less damaging to roads and cars, it has a downside. Sand can’t be used in cities or areas where there are sewer drainage systems that rely on pumps, due to the damage it can cause.
Rumor has it that the beet brine mixture smells kind of like Tootsie Rolls! And no, it doesn’t look like the roads are covered with beet-red blood. Made from the white-fleshed sugar beet, the solution is brown and non-staining.
Photo credits: red beets by University of Michigan Campus Farm; sugar beet by MichiganGrown.org.