ORONO, Maine — Tree pulp and seaweed — two readily available natural resources in Maine — could replace the harmful coatings of “forever chemicals” that had been used widely until recently in food wrappers if several projects underway in the state reach commercial production.
University of Maine researchers are developing highly refined pulp cellulose and seaweed coatings that could add grease- and oil-resistance properties to paper. They are similar in function to, but safer than, certain PFAS, or per- and polyfluoroalkyl substances, that have been used.
The paper industry has already expressed interest in potentially producing PFAS-free coated paper using the university’s work, although commercial production is several years off. A Portland-based start-up, Everything Seaweed, also is developing seaweed-based materials as an eco-friendly replacement for PFAS food packaging coatings.
Their work comes at a time when Maine lawmakers have made aggressive moves to require manufacturers selling products in the state to disclose which of them contain PFAS. The chemicals have been linked to various health issues, including kidney and testicular cancers, and decreased birth weights. In addition to getting on food through items such as fast-food wrappers, microwave popcorn bags and take-out paperboard containers, PFAS can get into drinking water sources after wrappers are discarded into landfills.
In February 2024, the U.S. Food and Drug Administration said substances containing PFAS used as grease-proofing agents on paper and paperboard that expose people through their diet are no longer being sold by manufacturers into the U.S. market. That adds to the incentive for Maine researchers to look into pulp and seaweed to develop eco-friendly coatings from materials that are abundant and inexpensive in the state.
“The state of Maine is good at making fibers,” said Douglas Bousfield, a professor in the University of Maine’s department of chemical and biomedical engineering, who is researching new coatings.
The market for single-use paper plates that need to be resistant to grease and wet foods is large. Some 226 million Americans will use disposable cups and plates this year, according to market research firm Statistica, up from the almost 220 million four years ago.
The strong market growth — and writing on the wall for PFAS use in all sorts of products — has chemical makers including Solenis, which is one target of a PFAS contamination lawsuit by Fairfield residents, developing their own PFAS-free products. Solenis sells a chemical solution not containing PFAS to be used with molded fiber containers such as salad bowls. Its coating, called Contour, uses water-based synthetic biopolymers, according to the company. Paper companies also are developing PFAS-free wrappers, including Twin Rivers Paper Co. in Madawaska.
“I think the companies are smart enough to know that they have to stay away from PFAS, so they’re probably using a totally different chemistry,” said Colleen Walker, director of the Process Development Center at the University of Maine. “The problem is, PFAS does a really, really good job, so people will have to change their expectations for alternatives” that may not work as well.
Paper products with alternative coatings could cost 1 cent higher or even more than traditional products, Bousfield said, which adds up with high volume purchases.
There also are technical challenges ahead for the highly refined cellulose coatings with which University of Maine researchers are experimenting. One is scaling up its coating technique to make large volumes of coated paper. The technique currently involves spraying a grease-resistant coating onto paper, but it does not yet spread evenly on flat or curved paper surfaces, nor can it be applied at high speed, two challenges the researchers are working to resolve.
The other challenge is that businesses that adopt and use the technology will have to buy new machines to apply the coating onto paper, Bousfield said. Still, paper companies could turn that into a potentially lucrative side business with this new grade of paper, he said. Already, paper companies in Maine, including Sappi, have expressed interest in the research at the university, he said.
To produce a highly refined cellulose coating involves grinding pulp fibers into nanoscale-sized particles as small in diameter as a human hair. The coatings are as thick as honey despite being made up of 97 percent or more of water, said Sandro Zier, a Ph.D. student in chemical engineering at the University of Maine.
“It is very, very hard to get it evenly coated onto paper,” he said.
Zier is collaborating with fellow chemical engineering Ph.D. student Bright Appiah to get a workable composition for the cellulose and a coating process that is high speed and high quality enough for commercial applications.
Their colleague Nabanita Das, a student in the university’s forestry school, has been testing paper plates sprayed with the experimental coating to see whether they block food oils of various thickness from absorbing into the paper. So far, results look promising.
Sanjana Mutyapu, who is working on her master’s degree in chemical engineering, is using seaweed to make a coating that can biodegrade on land and in the ocean. Plates coated with seaweed could add nutrients to gardens as they biodegrade, she said, just as pulp-based coatings can. PFAS chemicals contain a chain of linked carbon and fluorine atoms that is very strong, so they do not degrade into the environment, which is why they are known as “forever chemicals.”
Everything Seaweed, a Portland-based company, is discussing a collaboration on a possible pulp-based food container using its seaweed coating with the University of Maine’s Process Development Center, said company Chief Operating Officer Colin Hepburn, but talks still are in the early stages.
The company already has a prototype gel coating made from the leftover fibers not used by seaweed refinery companies. It washes the seaweed waste and compresses it to create long fibers for coatings. The company has a pilot plant to test the product, and it plans to invest about $6 million to build a factory in southern or central Maine in the next few years, Hepburn said.
The first products will be take-out boxes and quilted paper to wrap sandwiches. Hepburn sees a huge opportunity in the sustainable packaging market for both makers of containers and coatings, and for collaboration between them.
“This is a big opportunity for Maine,” he said. “And seaweed and pulp fibers are compatible at a molecular level.”
Lori Valigra is an investigative environment reporter for the BDN’s Maine Focus team. She may be reached at [email protected]. Support for this reporting is provided by the Unity Foundation and donations by BDN readers.
