Erica L-W Majumder might be an alchemist. Her goal? Turn trash into environmental gold. This assistant professor of bacteriology believes landfills like the one across from the Yahara Hills Golf Course in Madison are treasure troves of scientific — and commercial — discovery.

She imagines a future in which today’s oil-based plastics are replaced by bioplastics — plastics that degrade easily and swiftly because they are created from organic sources such as sawdust. Today bioplastics make up only a tiny percentage of the world’s output. Majumder believes that with some help from microbes, perhaps relatives of those in landfills, these new, friendlier plastics will lead an economic revolution.

This idea is part of what Majumder calls an emerging circular bioeconomy. The concept of an economic system powered by nature has been around since the late 1980s but has only recently started to gain traction. It’s a vision that could give a huge boost to Wisconsin’s $2.3 billion plastics industry, which employs 43,000 people.

“We need to think strategically about the materials we make,” says Majumder. “I’m optimistic that if we can leverage what’s in landfills and the infrastructure of food processors, we will start to see this transition happen.”

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Majumder knows where buried treasure lies — in the depths of the Dane County Landfill. During the COVID lockdown, landfill administrators let Majumder and her graduate student team perform bioprospecting, sampling its contents from top to bottom. Some people might be bothered by working with trash. “But if you’re a microbiologist, you’re used to it,” she says. For her efforts, Majumder has been called “the landfill lady.” “I’m mostly okay with it,” she says. “Mostly.”

That moniker might be a badge of honor. Majumder knows of only a few other researchers working on landfill microbiology. “There’s not much interest now,” she says. “But people will start to be interested.”

Part of her fascination with landfills stems from their unusual characteristics — there’s nothing like them in nature. “It’s a completely different biogeochemical situation than we see in non-man-made environments,” she says. She’s on the cutting edge of a new field. As recently as 2016, no one even knew that certain bacteria could digest PET plastic (polyethylene terephthalate), one of the most used plastics in the world), and little is known about microbes that thrive in the bowels of landfills. Based on field samples Majumder took, she hopes to soon understand what these microbes are, how they relate to one another, and how they contribute to different biogeochemical cycles in landfills.

“If we can do undersea mining, we can go mining for microbes 100 feet down in a landfill,” she says. “We need to see what metabolisms are present, and since landfills are engineered and controlled environments, we need to stimulate those metabolisms to do something more favorable toward breaking down plastics.”

Another project on her to-do list is figuring out how to modify microbial gas production in the county landfill so that more of the gas takes the form of methane. The landfill already sends methane to its processing facility (the nation’s first), where it’s converted into renewable natural gas and injected into an interstate pipeline for use as vehicle fuel.

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Cans rust in landfills. Paper rots. Plastics, however, seem immortal. During Majumder’s landfill dig, she found plastic that had been buried more than 30 years. It remained “instantly recognizable,” she says. As a souvenir for her lab, she kept a brownie wrapper from a well-known mass producer of snack cakes. It looks like it was discarded yesterday.

Plastics comprise about 20% of the material in Wisconsin landfills, says the state’s Department of Natural Resources. And according to the Organization for Economic Co-operation and Development, each year the world produces about 400 million tons of plastic, an amount projected to triple by 2060. Worse, most of it is used once and thrown away. Much of that plastic waste ends up in the oceans.

Many challenges remain before the flood of oil-based plastics ends. Today’s bioplastics are brittle, and those made of petrochemicals are more flexible and stronger. That’s part of the problem with today’s plastics. Their chemical bonds are so strong that not even the hungriest microbe can do more than nibble at them. In other words, no known microbe can reduce today’s plastics to organic matter as quickly as paper disintegrates. For today’s plastics to be replaced by bioplastics, Majumder and other researchers must identify and grow plastic-eating microbes on an industrial scale.

“In a more ideal world, plastics probably wouldn’t even reach a landfill,” she says. Even these days, many municipalities have what are called MRFs, materials recovery facilities. Materials such as a plastic to-go container would be taken there. On-site would be a biological processing center that would break down the container to its chemical components. It would be like recycling — re-forming that material.

“We need bioplastics that can more easily be broken down to their monomer components so they’re not causing any further harm to the ecosystem,” Majumder says. “Microbes will be very a happy to eat them in their monomer form. We can upcycle that carbon into tens of thousands of different chemicals that will be useful bioproducts as part of a sustainable bioeconomy.”

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Sharp-eyed visitors to Majumder’s office notice a tote bag inscribed with a line that might be more at home in the English department. “I am excessively diverted,” reads the quotation from Jane Austen’s Pride and Prejudice.

Majumder has a restless academic mind. She is also pursuing, among other things, ways to clean uranium out of a Wyoming aquifer and whether microplastics in commercial poultry coops might lead to salmonella transmission in humans.

“I’m probably an extreme example of someone being highly, highly interdisciplinary across many different disciplines,” Majumder says. “The level of interdisciplinarity I have here would be impossible at most other institutions. There’s this ethos unique to UW–Madison. The collaborative culture here stems from the Wisconsin Idea.”

“It’s great to be in a lab as diverse as ours,” says Ph.D. student Chamia Chatman. Majumder oversees Chatman’s research into whether broiler chickens could replace rodents for research on environmental contaminants.

“To have to study just one thing can be very narrowly focused. It limits science,” says Chatman, who is in the Molecular and Environmental Toxicology graduate program. “It’s great we have people in our lab in biochemistry, toxicology, environmental chemistry and technology, and microbiology. We each add to the lab’s projects differently. Ultimately, we all use similar techniques and rely on each other for troubleshooting.”

A 2020 World Health Organization report suggested that microplastics might absorb contaminants, such as pathogens that transmit diseases. So, Chatman and Majumder asked this question: If broiler chickens sold by grocers have salmonella and microplastics in their digestive tracts, would that make the salmonella, which is typically not infectious among fowl, more dangerous to chickens?

Feedbags used by commercial chicken houses contain polyethylene. Majumder and Chatman exposed chicken gut cultures, not live birds, to polyethylene in both powder and fiber forms. They found that powdered plastic caused no response in microorganisms in chicken guts. The fiber, however, did cause a change. It created negative indications of gut microbe performance, according to Majumder.

Could this affect disease transmission to humans? “Potentially,” she says. “We didn’t measure that. We saw that salmonella was more disruptive when there was plastic and salmonella present than when salmonella was there alone.”

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Majumder’s passion for all things microbial began when she was a teenager. Her fascination with science fused with her passion for environmental justice. Many companies headquartered in her hometown of St. Louis operated lead mines around the world. Her church partnered with organizations in Peru and elsewhere to combat their pollution.

“I realized we didn’t have physical solutions to problems we were talking about,” she recalls. “My high school chemistry classes pointed me down the route into science and doing sustainability- focused research and, ultimately, waste management microbiology.” Plus, as an undergraduate at Drury University in Springfield, Missouri, she minored in global studies, something required of all students. This prodded her to think more about the ethical implications of her career.

She earned a Ph.D. in bioinorganic chemistry at Washington University in St. Louis. Her thesis explored the photosynthetic mechanisms that microbes use to convert and conserve solar energy. She did postdoctoral work at the University of Missouri–Columbia and the Scripps Research Institute, focusing on how metals and microbes interact in places fouled by nuclear waste.

That work continues today at the Riverton, Wyoming, Processing Site, an aquifer contaminated by uranium waste from an ore processing mill. Although uranium in groundwater is not radioactive, exposure to high levels can still cause health problems, so Majumder and Charles Paradis, an assistant professor of physical hydrogeology at the University of Wisconsin–Milwaukee, use a strategy called oxidative flushing to speed up the natural process of uranium removal tenfold. A well injects carbonate into the water to oxidize it. This solubilizes the uranium and pushes it out of the aquifer, much as a water softener rids drinking water of unwanted chemicals.

“My research philosophy tends to be more question driven,” Majumder says. “I use whatever technique is necessary to bring whatever other experts are necessary to answer a question.”

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Her collaborative spirit has led Majumder to do promising research on agricultural waste streams with Deepak Kumar, an assistant professor of chemical engineering at the State University of New York College of Environmental Science and Forestry. They hope to convert waste such as acid whey, wood chips, industrial hemp residues, and corn stover (stalks, leaves, and cobs left after harvesting) into microbial polymers that can be turned into bio-based biodegradable plastics.

Kumar’s and Majumder’s research specialties mesh particularly well. “She knows science, and I know engineering,” says Kumar.

One particular microbial polymer class — polyhydroxyalkanoates (PHA) — is already being used industrially to make bio-based biodegradable plastics. Many different species of microbes naturally produce this polymer as an energy-storage molecule when they are having difficulty finding nutrients.

Majumder and Kumar have found that by adjusting the pH level of acid whey (a yellowish liquid left over after the production of cottage cheese and Greek yogurt) and providing optimal nutrients, certain microbes can efficiently convert the whey’s lactose and lactate into PHA — specifically polyhydroxybutyrate — which is fully biodegradable.

Meanwhile, Kumar performs a techno-economic analysis to determine whether the process is commercially feasible. He crunches the numbers into process models to determine the necessary capital investment, the operational costs, how much energy will be required, and, most important, whether the final product will be profitable.

“The results are looking very promising,” says Kumar. His preliminary data show that using acid whey will significantly reduce the production cost of biodegradable bioplastics. Currently bioplastics are produced from corn syrup, corn sugars, or sugar cane sugars — all food products that have value.

By using acid whey, a bioplastics manufacturer can avoid the expense of using a corn syrup or sugar because acid whey is a waste material. The dairy industry has to pay money to dispose of it. “Because it’s sent to wastewater treatment facilities or spread in fields, it’s a negative cost,” says Kumar. “The productivities of our research are looking very good, very similar to what we get from sugar-based crops. That’s why we are very hopeful it will be feasible.” “We have to do a lot of work to scale this to the industrial level,” Majumder admits. “But we feel encouraged. We’ve found a waste stream where we could convert all its carbon and still obtain high yields.”

She believes that in 10 years food processors might make profitable use of acid whey. “They already have so much of the infrastructure that’s needed,” she says. “They do fermentations making beer and yogurt. The process of growing microorganism out of acid whey is very similar.”

The bigger hurdle is the physical space required and the capital investment. The challenge is how to scale up from successful lab demonstrations to 10,000-liter fermenters.

The gap between lab and factory is called “the valley of death” because many technologies fail to leap that hurdle. “There are a lot of discussions about how to design our lab experiments so they will scale,” Majumder says. “There are financial and policy considerations well out of the scope of what a microbiologist can do. But we’re starting to get there. That’s exciting.”

Erica Majumder acknowledges the valuable contributions that the following students made to the projects highlighted in this article: Damayanti Rodriguez-Ramos (landfills), Fuad Shatara (harmful algal blooms), Catherine Pettinger (uranium), and Rachel Rovinsky and Rob Mejia (bioplastics).