Trash to treasure: Leveraging industrial waste to store energy
Northwestern researchers introduce new players in the field of green batteries
image:
Emily Mahoney works on redox flow battery production.
view moreCredit: Malapit Lab/Northwestern University
- First time unwanted organic waste product used in redox flow battery research
- Battery discharged over 350 times without losing capacity to store energy
- Organic redox flow batteries are nearing commercial viability for grid-scale applications
EVANSTON, Ill. --- The batteries used in our phones, devices and even cars rely on metals like lithium and cobalt, sourced through intensive and invasive mining. As more products begin to depend on battery-based energy storage systems, shifting away from metal-based solutions will be critical to facilitating the green energy transition.
Now, a team at Northwestern University has transformed an organic industrial-scale waste product into an efficient storage agent for sustainable energy solutions that can one day be applied at much larger scales. While many iterations of these batteries, called redox flow batteries, are in production or being researched for grid-scale applications, using a waste molecule — triphenylphosphine oxide (TPPO) — marked a first in the field.
Thousands of tons of the well-known chemical byproduct are produced each year by many organic industrial synthesis processes — including the production of some vitamins, among other things — but it is rendered useless and must be carefully discarded following production.
In a paper published today (Jan. 7) in the Journal of the American Chemical Society, a “one-pot” reaction allows chemists to turn TPPO into a usable product with powerful potential to store energy, opening the door for viability of waste-derived organic redox flow batteries, a long-imagined battery type.
“Battery research has traditionally been dominated by engineers and materials scientists,” said Northwestern chemist and lead author Christian Malapit. “Synthetic chemists can contribute to the field by molecularly engineering an organic waste product into an energy-storing molecule. Our discovery showcases the potential of transforming waste compounds into valuable resources, offering a sustainable pathway for innovation in battery technology.”
Malapit is an assistant professor in the department of chemistry at Northwestern’s Weinberg College of Arts and Sciences.
A small part of the battery market at present, the market for redox flow batteries is expected to rise by 15% between 2023 and 2030 to reach a value of 700 million euros worldwide. Unlike lithium and other solid-state batteries which store energy in electrodes, redox flow batteries use a chemical reaction to pump energy back and forth between electrolytes, where their energy is stored. Though not as efficient at energy storage, redox flow batteries are thought to be much better solutions for energy storage at a grid scale.
“Not only can an organic molecule be used, but it can also achieve high-energy density — getting closer to its metal-based competitors — along with high stability,” said Emily Mahoney, a Ph.D. candidate in the Malapit lab and the paper’s first author. “These two parameters are traditionally challenging to optimize together, so being able to show this for a molecule that is waste-derived is particularly exciting.”
To achieve both energy density and stability, the team needed to identify a strategy that allowed electrons to pack tightly together in the solution without losing storage capacity over time. They looked to the past and found a paper from 1968 describing the electrochemistry of phosphine oxides and, according to Mahoney, “ran with it.”
Then, to evaluate the molecule’s resilience as a potential energy-storage agent, the team ran tests using static electrochemical charge and discharge experiments similar to the process of charging a battery, using the battery, and then charging it again, over and over. After 350 cycles, the battery maintained remarkable health, losing negligible capacity over time.
“This is the first instance of utilizing phosphine oxides — a functional group in organic chemistry — as the redox-active component in battery research,” Malapit said. “Traditionally, reduced phosphine oxides are highly unstable. Our molecular engineering approach addresses this instability, paving the way for their application in energy storage.”
In the meantime, the group hopes other researchers will pick up the charge and begin to work with TPPO to further optimize and improve its potential.
The research was supported by a start-up grant from Northwestern, the Department of Energy’s Office of Basic Energy Sciences (DE-FG02-99ER14999) and the National Science Foundation Graduate Research Fellowship.
Battery discharging [VIDEO] |
Journal
Journal of the American Chemical Society
DOI
New research improves predictions for solid waste management
North Carolina State University
A new approach for predicting the contents of municipal solid waste can help improve the efficiency of recycling and landfill operations. The new method applies a conventional approach to forecasting how many total tons of solid waste will be generated at the county level and incorporates a separate, complimentary model that predicts the makeup of the waste with an unprecedented level of detail.
“The effect of our new approach is that solid waste managers can forecast a detailed breakdown of the different materials that will make up the waste stream in addition to the overall tonnage of waste they might expect in the coming year,” says Adolfo Escobedo, co-author of a paper on the work and an associate professor in North Carolina State University’s Edward P. Fitts Department of Industrial and Systems Engineering.
“The diverse materials that end up in the waste stream are managed differently, particularly when attempting to implement a sustainable operation,” says Joshua Grassel, corresponding author of the paper and a Ph.D. student in the operations research graduate program at NC State. “It’s useful for managers to have a good idea of what sorts of materials they’ll be getting, and in what amounts, so that they can plan for how to process those materials. Some things can be recycled, some can be composted, and so on. Different types of infrastructure are required to process the array of materials, and proper planning is critical for making sustainable waste management a practical reality.”
Historically, waste managers have relied on simple models for forecasting the overall tonnage of solid waste that will be produced each year at the county level. But attempts to predict the composition of that waste have been somewhat limited, with few models attempting to break the overall waste stream down in any significant detail.
“One of the problems that previous modeling attempts ran into was that they were trying to predict the amount of each material present in the waste stream directly,” Escobedo says. “In other words, they were trying to predict how many tons there would be of each category of waste. This was challenging, even when evaluating only a limited number of categories. We took a different approach, adopting a two-phased strategy.”
Specifically, the researchers tailored a model to focus on solid waste composition by evaluating what proportion of the waste would fall under each waste category. The end result is capable of estimating municipal solid waste composition across 43 comprehensive material categories, ranging from aluminum cans to food waste.
Users can then couple the outputs from the waste composition model with predictions of total solid waste from well-established techniques.
“For example, if the model for waste tonnage predicts there will be 1,000 tons of solid waste, and the composition model predicts that 25% of the waste will be food waste, you end up with a prediction of 250 tons of food waste,” Grassel says.
“In addition to providing new insights for waste managers, this is a significant advance because there had previously been no central repository of data on waste compositions,” Escobedo says. “Lack of easy access to data has hampered efforts to develop robust solid waste forecasting tools. So a secondary, supplementary contribution here has been to compile this data and make it publicly available. It was certainly valuable in developing our modeling toolkit, and we’re optimistic it will facilitate additional work by other researchers in the field.”
To validate their approach, the researchers ran three case studies using real-world data.
“The results are promising – we certainly established proof-of-concept for this approach to solid waste forecasting,” Grassel says.
“However, we also know there is substantial room for improvement. We are already working with colleagues to incorporate more nuanced statistical modeling techniques to this framework – and are receptive to collaboration opportunities,” Escobedo says.
The paper, “Predicting the Composition of Solid Waste at the County Scale,” is published in the journal Waste Management. The paper was co-authored by Rajesh Buch of Arizona State University (ASU). The authors wish to acknowledge the Arizona Board of Regents for partially funding the work as part of project TRIF: Supporting and Increasing Recycling Around Arizona. They also acknowledge the other contributing members of the project team at ASU (Jen Clifton, Kazi Wahadul Hassan, Teja Phani Kumar Kadimi, Pitu Mirchandani, and Nivedita Rengarajan), at Northern Arizona University (Darren Bingham and Richard Rushforth), and at the Arizona Department of Environmental Quality (J.B. Shaw).
Journal
Waste Management
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Predicting the Composition of Solid Waste at the County Scale
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