Robert Ross & Shayne Martin – USDA Forest ServiceForest Products Laboratory
A year ago, the Forest Products Laboratory staff received a unique request.
That request came through a relationship built on cooperative research between the Department of Defense and the U.S. Department of Agriculture Forest Service, Forest Products Laboratory (FPL). This connection resulted in an amazing story of a 3,000-lb stack of legacy mahogany and other vintage lumber of incalculable value being used in the restoration of many historical wood objects at the U.S. Capitol building.
While our country reflects on the attack of January 6, 2021, which resulted in the damage or destruction of many treasured historical artifacts, we also reflect on the story of the wood used to repair what was thought to be irreplaceable. That story shone as a bright light and sign of hope in an otherwise dark situation.
Charles Frihart – or Chuck, as he prefers to be called – has just retired after 20 years with the Forest Products Laboratory. Before that, he worked in industry even longer. The total experience has left him with a unique perspective.
“Before FPL, I spent most of my time in New Jersey,” Chuck reminisced. Even though he lived and worked there for most of his career, Chuck says that he and his family always said we were temporary residents of New Jersey, “because we always considered Wisconsin home.”
Chuck started out working for a pulp and paper company. He then joined Henkel, which is the world’s largest adhesive company.
Chuck says he was happy to have the opportunity to return to Wisconsin in 2001 to work at FPL. His job was to modernize the wood adhesive group through his knowledge of adhesives in non-wood fields.
When paper pulp is manufactured, lignin and other parts of the wood are removed to release cellulose fibers. These byproducts form “black liquor,” which is seven times more abundant than the final paper pulp. This material is concentrated and put through a recovery boiler to recycle the pulping chemicals and provide energy. The pulping by-products are converted into chemicals for adhesives, printing inks, fragrances, and other products.
In industry, Chuck worked on what to do with chemical byproducts from the pulping process.
“I was mainly working with the fatty acids and what to do with them,” explained Chuck. “Fatty acids are similar to hydrolyzed vegetable oil. Basically, I was working on adhesives for many applications and generated 29 patents.”
Chuck’s interest in bio-based compounds goes back to his college days.
“I’ve always studied these natural products from my work on nucleic acids in college, through industry work on fatty and rosin acids, and at FPL on protein adhesives.
“I was hired at FPL not because I knew a lot about wood adhesives, but because I knew adhesives in general,” Chuck continued. “I was also brought in because FPL wanted someone with a different perspective, which meant being comfortable with working in industry.
“Most of my years with the paper industry, we had a very good executive vice president who wanted people to do a combination of applied and fundamental research. Sometimes you have people who are very good at fundamental research and spend all their time doing it, but have no idea how to make useful products, and the people in industry tend to get so attached to doing the applied work, that they forget fundamental science, so you have to think on both levels, because they’re not mutually exclusive.
“They complement one another and you can make more progress when you combine the two. My goal has always been to make something new, but at the same time understand the fundamentals as well as I can, and not get tied up in either one.
“Trial and error only gets you so far, so my thing has been to really understand how wood adhesives work and why they fail. Wood adhesives don’t normally fail except under wet conditions, and in some cases, with some of the adhesives applications, you also need temperature resistance, as in a fire, and that was a problem.”
The adhesives group needed a team of specialists in material science, analytical chemistry, mechanics and wood chemistry. The first addition involved Chuck’s welcoming Daniel Yelle, who does adhesive chemical reactions with wood polymers and lignin chemistry. “We have studied lignin, but few people have figured out how to get useful adhesive products out of lignin,” explained Chuck. “Although there have been about 200-some papers that have claimed that success, it’s actually only used marginally on a commercial level.
“The other area for bio-based adhesives is proteins, and soy beans specifically,” said Chuck. “Besides oil and protein food products, it’s basically used as animal food. We don’t produce much tofu or other kinds of fermented soy-based products for people as they do in China and other parts of East Asia. Also, soybeans have a high percentage of lysine, which is an amino acid and an important nutrient for animals.”
Chuck said that it is very difficult to understand proteins in adhesive applications because proteins can change properties very easily, and it’s hard to measure when the properties of proteins change. Chuck pointed out that soy is the major product that has been used in interior wood adhesives in the United States for over 10 years.
Among the major accomplishments in wood adhesives at FPL, Chuck points to the work of Joseph Jakes and Nayomi Plaza Rodriguez, “because they have developed an understanding of the fundamental structure of wood cell walls.”
Joseph works with Argonne National Laboratory, and Nayomi works with Oakridge National Laboratory, both run by the Department of Energy. Chuck said that the major advantage to these collaborations is that the other labs have extremely expensive experimental equipment and allow FPL scientists to write proposals and have access to it. “What makes us different is that we combine chemical probes made by Linda Lorenz with the analysis of wood cell walls to understand how adhesives react with wood itself,” said Chuck.
“The real challenge with adhesives is that they typically only work well only under dry conditions. It’s when things get wet that many of the adhesives fall apart and you have joints coming apart on wood products, et cetera. And so you have to understand the wood swelling and shrinking properties and how it’s doing that, and what Joseph and Nayomi and the others have done is just fantastic. So I can’t claim credit; I had the concept, but I didn’t know how to do it, so my role was more of an instigator, rather than the person who figured out how to do it. And it made FPL the leader in understanding wood cell walls and the behavior of wood.
“FPL is fortunate to have a core of very bright young scientists who can carry us through for the next few decades and who are doing things that nobody else is doing.
“At a certain point,” Chuck said wistfully, “your science becomes dated, and you need to be replaced by people who have different knowledge and abilities of how to carry out science. I’ve enjoyed the science and the people at FPL. Being involved in science is in my blood and will continue, just on a lower priority.”
The article “Lightweight Strong Moldable Wood Via Cell Wall Engineering as a Sustainable Structural Material,” coauthored by Forest Products Laboratory research scientists Junyong Zhu, Vina Yang, and Marco Lo Ricco, with lead author Prof. Liangbing Hu at the University of Maryland-College Park, was published in the Oct. 22, 2021 issue of Science Magazine as the cover article.
“In this work,” the article states, “we demonstrate how cell wall engineering can render wood foldable and moldable while simultaneously improving its mechanical properties – endowing wood with a structural versatility previously limited to plastics and metals.”
Research Forest Products Technologist Xiping Wang has recently been announced by Forests Magazine as a winner of the Best Cover Awards for his collaboration on the cover article “Non-Destructive Evaluation Techniques and What They Tell Us about Wood Property Variation.”
“A few years ago, Laurence Schimleck, the senior author of this article, and I met at a professional conference and discussed the possibility of writing a comprehensive review paper on a range of nondestructive testing technologies for wood quality assessment, especially on standing trees in forests,” Xiping explained. “My expertise is primarily in developing acoustic wave-based technologies for wood quality evaluation. In this article, I contributed two sections: Acoustics and Pilodyn, as well as some contents in discussions and tables.”
Xiping was also the photographer for the photo chosen by Forests for its cover.
The Technical Session of the American Paper and Pulp Association, or TAPPI, has recognized one of our own, Research Chemical Engineer Carl Houtman, for its 2021 Leadership & Service Award and Joseph K. Perkins Prize.
The citations states: “This award recognizes individuals for outstanding leadership and exceptional service, resulting in significant and demonstrable benefits to the Division’s members.”
“I’d like to thank the FPL for its support of my involvement in TAPPI,” said Carl. “I’m being honored because I was the public face in the projects. It’s the support scientists, technicians, and shop folks who’ve really made the work possible.”
Carl joined us at the Forest Products Laboratory in 1991, after earning his PhD in chemical engineering at the University of Delaware and pursuing postdoctoral study abroad. His work at FPL has focused on a wide range of complex projects in the paper industry.