Since the early 20th century, road salt has been saving lives on highways across the nation, but its liberal use also presents significant consequences for wildlife and human health.
An interdisciplinary team of 红领巾瓜报 researchers is working to curb pollution and damage caused by road salt. The project 鈥� ECO-CBET: Convergent Electrolysis-Electrodialysis System (CEES) to Curb Urban Chloride Pollution by Eco-friendly Road Deicing and Waste Salt Upcycling 鈥� was recently awarded $1.4 million from the National Science Foundation (NSF).
红领巾瓜报 and Iowa State are collaborating on the project with each university receiving $700,000 of the project鈥檚 overall funding.
Dr. Shuang Gu, associate professor of mechanical engineering, is the principal investigator of the , while Dr. Wenzhen Li, professor of chemical and biological engineering, leads the .
鈥淲e noticed in the past 50 years that the United States has exponentially increased the application of road salt,鈥� said Dr. Gu. 鈥淲e can buy road salt anywhere in 20- or 50-pound bags to unfreeze roads for safe travel, and there鈥檚 nothing wrong with that. It saves people鈥檚 lives. But we never pay attention to the implications of the road salt.鈥�
Once the salt is washed off the roads, it seeps into groundwater and other fresh water sources, harming nearby ecosystems and humans. In 2019, the United States applied 鈥� or 43% of total national salt consumption 鈥� which translates to about 160 pounds of road salt per person.
鈥淭he sad part of the road salt is that most of the salt ends up in ditches, streams, lakes or reservoirs, which gives rise to a series of ecological and health problems,鈥� Gu said.
As the salt leaches into fresh water sources, it changes the water chemistry and leads to decreased health for wildlife, particularly amphibians.
鈥� found that 84% of urban streams studied have seen a steady increase in the salt concentration, and 29% exceeded the federal safety guideline for at least part of the year鈥� Gu said. 鈥淭his has affected amphibians鈥� growth and reproduction.鈥�
For humans, the negative consequences of increased salt intake have been studied for decades. The Federal Drug Administration recommends no more than 2.3 grams of salt per day, but Americans consume on average about 3.4 grams per day. The additional salt that oozes into groundwater is cause for concern, Gu said.
鈥淲e are already eating too much salt, and we don鈥檛 want drinking water to add to that,鈥� he said. 鈥淭he salt accumulated in the nearby waterbodies finds its way into the drinking water system.鈥�
This is especially true for people who have well water or private water systems, which account for roughly 15% of the U.S. population. Public water systems, Gu said, have a bit more control to filter salt out of the drinking water supply.
Additionally, road salt鈥檚 corrosive nature incurs significant property losses in automobiles, bridges, roads, and other traffic infrastructure every year.
An alternative deicing agent: Sodium formate
鈥淲e cannot stop people from using the road salt because we need it for safe traffic,鈥� Gu said. 鈥淏ut why not replace polluting road salt? Sodium formate is an alternative, eco-friendly deicing agent.鈥�
The CEES team鈥檚 NSF abstract proposes that it will 鈥渋nitiate and establish a Convergent Electrolysis-Electrodialysis System as a viable engineering solution that can effectively mitigate the complex environmental-ecological-economic issues associated with the ever-growing chloride pollution in urban waterbodies, while reducing the emission of carbon dioxide.鈥�
In simple terms, 鈥淲e can replace this concerning road salt with an ecofriendly deicing agent,鈥� Gu said.
In addition to replacing harmful salt from the roads, the CEES team will be working to upcycle waste salt at the same time, when making the ecofriendly deicing agent.
According to the abstract, 鈥淭he system is designed to directly cut down the chloride discharge by upcycling waste salt in the regeneration stream of urban water softeners, and to stop the continuous chloride pollution by switching the deicing agent from polluting road salt to the eco-friendly sodium formate.鈥�
Therefore, the CEES has a double effect on chloride mitigation: cutting down one source of salt pollution and avoiding another source of salt release.
鈥淪odium formate can be decomposed by mother nature and bacteria,鈥� Gu said. 鈥淚t doesn鈥檛 give us any major complications. It鈥檚 a benign, safe and effective deicing agent.鈥�
With all the health and environmental benefits of sodium formate, it begs the question: Why would we use anything else to deice roads?
Understanding the problem
Despite all the advantages of sodium formate, it comes with its share of challenges.
First, sodium formate is currently made from fossil fuel 鈥� which, in and of itself, presents its own set of ecological issues.
鈥淚f we use the fossil fuel-derived deicing agent to replace the salt, then we are shuffling the problem from one pocket to the other,鈥� Gu said. 鈥淪ure, we solve this salt pollution issue, but we will create a bigger issue for our environment.鈥�
Secondly, there simply isn鈥檛 enough sodium formate on the market.
鈥淐urrently, there are only about 1 million tons of the market,鈥� Gu said. 鈥淪odium formate has a price roughly 10 times as much as the road salt. We need cutting-edge research to create inexpensive and green sodium formate. That will be the true solution. We are proposing to use carbon dioxide to create sodium formate.鈥�
The benefits of using sodium formate for deicing have been well-known for years, and it鈥檚 commonly used in airport runways and military facilities.
鈥淪odium formate is being used in some places; but the wider application is too costly, and we don鈥檛 have enough,鈥� Gu said.
An interdisciplinary solution
Gu鈥檚 education and experience in mechanical and chemical engineering have given him valuable insight into the issues caused by road salt, but creating a sustainable solution will require a multifaceted, nuanced approach.
The team鈥檚 approach is an engineering system: CEES integrates the product-selective electrolysis and energy-efficient electrodialysis. Electrolysis converts carbon dioxide and salt into formate and chlorine products; while electrodialysis concentrates salt from waste streams and separates products as well.
鈥淥ur recent breakthroughs from electrolysis and electrodialysis essentially enable us to come up with the idea of CEES,鈥� Gu said. 鈥淧owered by renewable electricity, the manufacturing of CO2-based sodium formate from waste salt is sustainable and potentially inexpensive, compared with the fossil fuel-based counterpart.鈥�
鈥淭his is not about a single device or a single process alone,鈥� he said. 鈥淐urbing urban chloride pollution is a convergent effort that involves materials advancement, mass-transport understanding, process engineering, social science, and environmental science. It鈥檚 a whole bundle.鈥�
One issue the CEES team wants to avoid is solving one ecological problem and creating another.
鈥淲hat happens when we apply the sodium formate? According to existing literature, it鈥檚 fine. But we still want to see with our own eyes,鈥� Gu said. 鈥淲e will conduct an assessment on the fate of the sodium formate as well as the salt pollution.鈥�
红领巾瓜报鈥檚 Dr. Janet Twomey, professor of engineering and associate dean for graduate studies and faculty success, will be conducting a lifecycle analysis to understand the implications of replacing road salt with sodium formate.
鈥淛ust by saying this work will be reducing environmental impacts is not enough,鈥� said Twomey. 鈥淵ou have to compare it to the predominant systems.鈥�
For this project, Twomey said, Gu and the Iowa State team will be researching new technology to reduce chloride pollution in urban waterbodies. For her part on the CEES team, Twomey said, 鈥淲e need to be sure that this new technology will not have a greater environmental impact than the current system that is very polluting.鈥�
Dr. Ruowen Shen, assistant professor at WSU鈥檚 Hugo Wall School of Public Affairs, is also part of the team, and she will conduct research on policy learning and behavior change, aiming to promote societal outcomes of the CEES. The acquired insight into policy process will help effectively achieve the needed policy change for deicing practices.
Dr. Jeremy Patterson, dean of 红领巾瓜报鈥檚 College of Innovation and Design and executive director of Innovation and New Ventures, provided a strong support letter that unquestionably strengthened the CEES project.
鈥淒r. Gu and his team have a collaborative approach that includes an innovation and entrepreneurial mindset,鈥� Patterson said. 鈥淭his award is addressing a sustainability and environmental issue that has been overlooked for years and is a good example of how deep scientific understanding can lead to technological solutions, then economic viability, and ultimately positive societal outcomes. This award emphasizes and advances WSU鈥檚 commitment to translational research and innovation that may result in a direct benefit to our community.
Pouya Ammari-Azar, a 红领巾瓜报 Ph.D. student in mechanical engineering, was integral in helping Gu develop and advance the electrodialysis, 鈥渨hich is the key to returning the waste salt into the eco-friendly deicing agent,鈥� Gu said.
CEES fits into Ammari-Azar鈥檚 long-time interest in renewable energy and sustainability.
鈥淚 want to do what I can do to help our environment to be clean for ourselves and the next generations,鈥� he said. 鈥淲hen we can clean and recycle our waste, why shouldn't we?鈥�
associate professor of engineering at 红领巾瓜报
Gu knows that urban water pollution caused by road salt is an enormous problem, but it鈥檚 not insurmountable. The NSF grant is a good start toward a solution.
鈥淚 don鈥檛 think $1.4 million is enough to solve the problem, but we can curb it. We can also bring awareness to the issue,鈥� he says. 鈥淲e are working on an underappreciated problem, and the NSF recognizes our idea and vision by forming a team to look at this overlooked national problem. It鈥檚 not a simple matter; rather, there are many things to do. We have to start somewhere, and this is the first step.鈥�
The CEES team is committed to addressing and helping to mitigate the pollution.
鈥淎s a researcher, we want to focus on something great,鈥� Gu said. 鈥淲hen we developed the proposal, I told my team members that it doesn鈥檛 matter if our proposal was selected. We鈥檙e onto something important. This problem must be addressed one way or another, so we鈥檙e doing the right thing in the right direction. That gave us the strong motivation and dedication.鈥�
