UVM Researchers Team Up with Casella to Uncover the Suitability of Packaged Food Waste for Organics Recycling
More than one-third of food waste in Vermont is still packaged—a sticky situation when it comes to mandatory diversion of food waste away from landfills under the state’s new Universal Recycling Law. Act 148 banned food scraps from landfills beginning in July 2020.
“It’s very exciting for us to bring this technology to our home state,” said John W. Casella, chairman and CEO of Casella Waste Systems, Inc. “This facility will allow us to separate valuable organic and recyclable feedstock from waste material, put them to a higher and better use, and preserve natural resources.”
Casella has funded a pair of UVM graduate students to conduct this sustainable waste management research. Assistant Professor Eric Roy and two of his graduate students are determining if food waste, once separated from its packaging, can be used in anaerobic digestion and composting.
As an alternative to composting, food scraps, often in combination with dairy manure, are broken down by microorganisms in the oxygen-free containment of an anaerobic digester. The process produces biogas, a clean, renewable source of energy. Along with biogas, anaerobic digestion produces liquid and solid digestates, commonly spread on farm fields as fertilizer, used for animal bedding, or composted.
But what happens if the separated food waste still contains small particles of packaging—mostly plastics? The de-packager’s manufacturer claims a 95 to 99 percent effectiveness in isolating food from its containers. That leaves a small fraction of microplastics which can make its way into the environment when the food waste is incorporated into the soil as digestate or composted.
“Casella is being very proactive in determining how well its de-packaging facility works to maximize environmental benefits and minimize cost,” said Roy, a UVM faculty member in both the Rubenstein School of Environment and Natural Resources and the College of Engineering and Mathematical Sciences (CEMS). “We are trying to establish data that can guide food waste management into the future in Vermont and beyond.”
Casella and the researchers focus on two main streams of packaged food waste: pre-consumer—usually large quantities of packaged, but unsaleable, product from food makers—and post-consumer, which can contain packaging or other contaminating materials. Roy and his students are testing both streams of de-packaged food waste. They are quantifying its value for biogas production and composting and its plastic contamination.
“I got to sit down with folks at Casella and come up with research questions through dialogue about our mutual concerns and interests in the environment and waste management,” said Kate Porterfield, a PhD student in CEMS, who is evaluating the suitability of the de-packaged food waste for use in biogas production.
Porterfield began her research at the facility in January 2021, on the day Casella ran its first load in the de-packager. She watched operators load packaged food waste into the hopper, where rotating paddles broke open the packaging without shattering it. The separated food waste passed through screens, and the packaging was lifted out to be recycled or sent to the landfill. Porterfield collected samples of food waste after the separation process for testing in the laboratory.
Science to Solutions
The support from Casella has allowed Porterfield and Roy to pioneer new ways to measure plastics in food waste. Porterfield is working on methods that quickly and easily isolate and quantify the abundance of microplastics. Marine scientists do similar work to study plastics in oceans.
Porterfield uses an instrument called an Automated Methane Potential Test System (AMPTS 2), a lab-bench-scale anaerobic digester that runs 15 soft-drink-sized bottles of food waste samples at once. Each time a sample creates methane, a computer records gas bubbles and creates a graph of biogas production. This helps the researchers to determine how efficiently food waste can be turned into biogas.
After the organic waste is digested, tiny pieces of plastic can be easily removed using a fine mesh sieve. Porterfield counts the particles under a microscope to see how much plastic is contaminating the organic matter. She then uses Fourier Transform Infrared (FTIR) spectroscopy to classify the polymers of plastic isolated from the lab digestion process.
“Once we identify the types and amounts of contaminating plastic, Casella and others in the industry can go back upstream to the food manufacturers or waste suppliers to seek ways to remove the unwanted packaging or other contaminating materials,” said Roy, a faculty fellow in UVM’s Gund Institute for Environment.
“Our findings are hugely important to Vermont’s Universal Recycling Law which necessitated this kind of research,” said Porterfield, a Gund graduate fellow. “There is so much we don’t know about using food waste, particularly the impacts of plastic contamination.”
UVM Master’s student Sarah Hobson will study de-packaged food waste, composting, and plastics contamination. She began her two-year program of study in the Rubenstein School this fall with a Sustainable Materials Management Fellowship funded by Casella.
“Can compost that contains microplastics be used safely in the environment?” said Hobson. “This is still a new field of study, and we are trying to get a better understanding of the life cycle of plastic in food waste.”
“We’re proud to work with a leading sustainability institution like UVM and to provide UVM students with meaningful research opportunities that will advance our industry,” said Casella. “To see the research have a practical effect in real time is very powerful, and we are grateful for the ongoing partnership and UVM’s shared commitment in advancing sustainable solutions for the environment.”
To help guide her work, Hobson will use participatory action research to learn firsthand from farmers, compost producers, and residential compost users what they know and what questions they have about plastics in food waste and compost.
Roy and his graduate students bring their research into the classroom to engage up to 50 undergraduate students each year in projects that become trial runs.
“Students get excited when they realize they are on the frontier of new knowledge and are involved in actionable science that will be used to improve the environment,” said Roy.
In Roy’s Advanced Ecological Design course last spring, an undergraduate student team ran anaerobic digestion experiments using de-packaged food waste and developed methods for microplastics separation.
“Working with Kate Porterfield and my group was easily the most fun and high-level learning project I have ever been a part of,” said UVM undergraduate Garrett Dunn. “The most important aspect was how we decided to work on a fairly new research discipline in waste management. This really made the learning experience very unique from any other class.”
This fall, a larger student group will learn about carbon cycling and food waste management using similar experiments in Roy’s Ecological Design and Living Technologies class. These hands-on learning experiences take place in a new Eco-Design Makerspace in the Aiken Center on UVM campus with support from Casella.
Learn more about Casella, a regional solid waste, recycling, and resource management services company headquartered in Rutland, Vermont.