Grad student turning trash into cash
Brooke Marten (left) and Prof. Sherri Cook following Marten's successful thesis defense July 1.
Brooke Marten (MEnvEngr’21, PhD’24) is engineering a better environment through high tech solid waste analysis.
Marten just completed her PhD in environmental engineering at the 鶹Ƶ, focused on what happens to trash after it is carted off to the landfill – and ways to turn it into a valuable product.
“My focus is on resource recovery of the organic fraction of municipal solid waste – food waste and yard trimmings,” Marten said. “You can recover valuable material that can be marketed and sold.”
Her research and PhD thesis used life cycle analysis to evaluate different solid waste strategies including composting, anaerobic digestion and especially pyrolysis, a method of breaking down organic material in the absence of oxygen at high temperatures – typically above 500 °C.
“Implementation of the more common organic waste management strategies, like anaerobic digestion and composting, has been slow, so we wanted to look particularly at the use of a novel strategy, pyrolysis, which showed real potential,” Marten said.
An emphasis of Marten’s work is how turning waste into a useful product can also reduce environmental impact. Pyrolysis results in a solid called biochar that can be used as a landfill cover material. It avoids the need to use soil or woodchips and reduces landfill emissions.
Pyrolysis can also treat landfill leachate, formed when rainwater filters through buried waste, and recovers syngas, which can be combusted for energy production.
“I have a draw to recover resources from something people view as trash, flipping the narrative. This shouldn’t be a burden; it is an opportunity to recover something,” she said.
Conducting life cycle analysis models the full implications of these environmental actions, providing a more complete picture.
“Carbon footprints are on everyone’s radar, and the analysis looks at that, but it’s actually quite a bit more complex – for example, we also look at each strategies’ potential to cause algal blooms, form smog, and contribute to ocean acidification. If our plan helps in one area but hurts in another, we want to avoid that,” she said.
The analysis also focuses on dollars and cents.
This shouldn’t be a burden; it is an opportunity to recover something." - Brooke Marten
“We can’t recommend something that’s great for greenhouse gas reduction but is totally unaffordable,” she said.
The desire for such a complete analysis grew during Marten’s undergraduate years as a civil engineering student at the University of Wisconsin – Madison. There, she observed a campus Styrofoam and foam packing material recycling program and wanted to know if was as beneficial as hoped.
“They recycled Styrofoam, but to do it they were driving these trucks all around picking it up. I wanted to know if that made sense or if it should just be landfilled,” she said.
She learned about life cycle analysis, but did not have the knowledge necessary to conduct one as an undergrad. It eventually led her to CU Boulder and Professor Sherri Cook, who is an expert in the methodology and would become her PhD advisor.
“It’s a very marketable skillset and I knew I had to go to grad school to do it,” Marten said.
Completing such analysis is resource-intensive. Marten developed computerized process models, adding variable after variable – waste mass, material composition, energy potential, and more, to present the most complete picture possible, as the ideal answer for one municipality may not work as well for another.
“Waste is so heterogeneous, and the solutions are not one size fits all. Some parts of the country really push collection of yard waste. Others emphasize foot scraps. That composition could change the answers,” Marten said.
Her PhD thesis, “Towards Sustainable Resource Recovery: Developing and Evaluating Novel Strategies for the Organic Fraction of Municipal Solid Waste,” is now complete and Marten successfully defended on July 1.
The next chapter of her life is with , where she has been hired as a sustainability engineer, a job rich in research and life cycle assessments.
“They work on a lot of novel concepts at national labs, and I love research,” she said. “I’m really excited about it.”