INFORM November/December 2025

inform November/December 2025 Volume 36 (10)

GOBS OF GLYCEROL

ALSO INSIDE: Biomass pyrolysis

PVC plasticizer from cashew nuts Cows prefer their soybeans roasted

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November/December 2025 inform

8 FEATURES

Gobs of glycerol: How a waste product could be a sustainable building block

Although glycerol is a valuable starting material, useful in multiple industries, the crude form produced as a biproduct of biodiesel manufacturing is challenging and expensive to purify. Nonetheless, researchers are seeking solutions to this purification problem. Is the answer biotransformations? Read this article to find out.

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Biomass pyrolysis: Liquid properties Bio-oil, the complex liquid produced by biomass pyrolysis, is emerging as a versatile renewable resource—used today as a fuel and food flavoring and explored for future roles in advanced biofuels, specialty chemicals, and sustainable materials. Cashew nut liquid as a PVC plasticizer Researchers show that cashew nutshell liquid, a non-edible byproduct of cashew processing, can be transformed into high-performing, sustainable plasticizers that rival and even surpass conventional phthalates for flexible PVC applications. Read about the physical properties associated with the bio-based plastics they created. Dairy benefits from high-oleic soybeans High-oleic soybeans are increasingly being adopted in dairy diets. They improve milk composition and reduce feed costs, while lowering the risk of milk fat depression, sometimes boosting milk fat yield and percentage. And the altered chemistry that comes with roasting the soybeans provides other benefits. Read this article to understand how high-oleic is helping farmers.

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CONTENTS

4 Index to Advertisers

5 Editor’s Letter 6 Division Update

29 Regulatory Review 31 Extracts & Distillates

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inform International News on Fats, Oils, and Related Materials ISSN: 1528-9303 IFRMEC 36 (10) Copyright © 2013 AOCS Press

EDITORIAL ADVISORY COMMITTEE

Julian Barnes Etienne Guillocheau Jerry King

Gary List Thais L. T. da Silva Raj Shah

Ryan Stoklosa Ignacio Vieitez Bryan Yeh

AOCS OFFICERS PRESIDENT: Gerard Baillely, Procter & Gamble, Mason, Ohio, USA VICE PRESIDENT: Fabiola Dionisi, Societe’ Des Produits Nestlé - Nestlé Research, Lausanne, Vaud, Switzerland TREASURER: Greg Hatfield, Bunge Limited, Oakville, Ontario, Canada SECRETARY: Roger Nahas, Kalsec, Kalamazoo, Michigan, USA PAST PRESIDENT: Tony O’Lenick, SurfaTech, Lawrenceville, Georgia, USA CHIEF EXECUTIVE OFFICER: Patrick Donnelly

AOCS STAFF EDITOR-IN-CHIEF: Rebecca Guenard MEMBERSHIP DIRECTOR: Travis Skodack

PAGE LAYOUT: Moon Design

The views expressed in contributed and reprinted articles are those of the expert authors and are not official positions of AOCS. Some articles may be written using an AI companion.

INDEX TO ADVERTISERS *CPM Crown. ......................................................................................................... C4 *Desmet USA, Inc................................................................................................... C2

*Corporate member of AOCS who supports the Society through corporate membership dues.

EDITOR’S LETTER

inform November/December 2025, Vol. 36 (10) • 5

Turning trash into a treasured biobased product

Innovation often begins where others see only waste. In this issue, we spotlight how research ers and industry leaders are transforming byproducts and overlooked resources into sus tainable solutions with broad applications. Crude glycerol, a biproduct of biodiesel production, is of low value due to contamination by methanol, water, sodium hydroxide, and residual impurities. Valorizing crude glycerol could make chemical manufacturing more sustainable and biodiesel production more economical. Our cover story this month describes the hurdles in the way of putting crude glyc erol to use and whether biotransformations hold the key to unlocking its full potential. Our article on biomass pyrolysis highlights the promise of bio-oil: a complex, versatile liquid with applications that stretch from energy to food flavorings to advanced materials. Its chemical diversity makes it both a challenge and an oppor

tunity for innovation in renewable resources. Could biomass pyrolysis offer new opportunities for multiple sectors? We then turn to cashew processing, where nutshell liq uid—once discarded as agro-waste—is emerging as a poten tial starting material for sustainable plastics. Researchers show that mixtures of cardanol and cardol can act as effective PVC plasticizers, offering safer, bio-based alternatives to phthalates without sacrificing performance. Together, these stories show how science is steadily rewriting the narrative around “waste”—turning what once seemed like a liability into a resource for the future. Disposal problems are now being reimagined as the foundation of greener chemistry and materials.

Yours in science,

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Industrial Oil Products Division

Congratulations to the 2025 Industrial Oil Prod ucts Division professional award winners: Nazanin Vafaei and Thomas H. Epps III!

INFORM: What has been the most rewarding experience or achievement in your career so far? And why? Vafaei: One of the most rewarding moments in my career was presenting my research on developing a methodology to extract more than 90 percent of canola oil using a combination of supercritical CO₂ and expeller pressing. This process not only achieves high oil recovery but also produces food-grade canola meal that is suitable to be incorportated into plant-based pro tein products for the food industry. Equally rewarding has been receiving the 2025 Early Career Grant of the IOP Division of AOCS. This recognition was deeply meaningful because it acknowledged the novelty and impact of my research while reinforcing the importance of advancing sustainable processing technologies in today’s food industry. Finally, mentoring students and postdoctoral peers has been an ongoing highlight. I find great satisfaction in support ing the growth of the next generation of scientists—watching their curiosity evolve into tangible results and celebrating their successes alongside mine. INFORM: What initially drew you to work with canola, and what excites you most about its potential in the food and oil industry? Vafaei: My journey with canola began when I recognized how underutilized and undervalued canola meal remains, despite being produced in large volumes in Canada. Canola is one of the most important crops globally, and its oil is already well known as one of the healthiest vegetable oils—naturally low in saturated fat and rich in unsaturated fatty acids—despite the myths and rumours that circulate online. At the same time, canola oil processing has tradition ally relied on hexane extraction, which is very effective for oil recovery. However, if we want to unlock the protein poten tial of the meal for food and feed applications, we need alternative approaches that operate at lower temperatures, preserve protein quality, avoid solvent residues, and are envi ronmentally friendly. What excites me most is the opportunity to transform canola co-products and oils into high-value ingredients—such as functional proteins and sustainable, high–melting point dia cylglycerol-enriched oils that can partially replace palm oil in food formulations. This approach not only enhances the over all value of canola but also supports global priorities: strength ening food security, reducing waste, diversifying plant-based protein sources, and advancing eco-friendly processing meth

Nazanin Vafaei

EARLY CAREER GRANT RECIPIENT Nazanin Vafaei is a postdoctoral researcher at the Richardson Centre for Food Technology and Research at the University of Manitoba, Canada. INFORM: What does this recognition mean to you, and how has it supported your professional development? Vafaei: Receiving the 2025 Early Career Grant from the IOP Division of AOCS is both a tremendous honor and a source of motivation. It validates my contributions to sustainable oilseed processing and highlights the importance of advancing green technologies in food science. The recognition has opened new doors for collaboration, expanded my professional network, and provided the opportunity to present my work to inter national audiences. Most importantly, it has encouraged me to think more boldly about the translational impact of my research—how discoveries in the lab can ultimately reach the marketplace and address global challenges such as food secu rity and sustainability.

with internships at Goodyear Tire & Rubber Company and Bell Laboratories along the way. In 2006, I began my faculty career at the University of Delaware in Chemical Engineering. I was extremely fortunate to land in such a collaborative and innovative department with wonderful colleagues and students. Those collabora tive interactions launched my journey into waste valoriza tion, which began through several conversations that involved Richard Wool and Joseph Stanzione (a graduate student of Wool’s at the time), and Angela Holmberg (a graduate stu dent of mine at the time)—one of the first conversations was at a departmental picnic. Wool was fascinated by opportuni ties to use various waste streams as feedstock for materials, and particularly those with some degree of aromaticity. Lignin rich waste was ideal in this regard, as the waste was cheap, abundant, underutilized, and could be sourced from renew able feedstock. As a team, we were able to study lignin and its deconstruction products, and we became excited about lignin-derived phenolics as possible alternatives to styrenics, bisphenols, and other building blocks. We are still excited by these possibilities and continue the effort to this day. INFORM: Your work has had a substantial impact on the field of polymer science and renewable materials. Can you discuss one or two key projects that you believe have made the most difference? Epps: There are two aspects of our work in polymer science that I would like to highlight. The first effort is our work that culminated in the design, generation, and characterization of block copolymer materials from real biomass (raw poplar wood) for use as pressure-sen sitive adhesives (PSA). We were able to demonstrate that fun damental understanding of the structure features inherent to lignin-derived aromatics (i.e., the methoxy substituents) enabled the design of PSA that were competitive with com YOUR AOCS COMMUNITY Thomas H. Epps III

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ods that contribute to both human health and the sustainabil ity of our planet. INFORM: In your view, what are the most critical chal lenges in improving canola oil and protein preservation, and how is your research addressing these issues? Vafaei: One of the most critical challenges is the reliance on solvent-based extraction methods, which, while effective for oil recovery and producing healthy oil, can compromise pro tein functionality. If we want to fully use canola meal as a pro tein source for food and feed applications, we need alternative approaches that preserve quality and avoid solvent residues. Another challenge lies in maintaining the delicate balance between oil stability and protein integrity during processing. My research addresses these challenges by develop ing solvent-free extraction methods, such as supercritical CO₂ and expeller pressing, while also testing novel strat egies to enhance antioxidant retention and protein func tionality. This work aims to provide the food industry with scalable, sustainable solutions that maximize the value of canola while meeting nutritional, environmental, and eco nomic goals. INFORM: Do you have any advice for the next generation of scientists and professionals in this field? Vafaei: My advice would be to embrace interdisciplinarity and collaboration. The challenges in food and oil science—whether sustainability, health, or processing efficiency—cannot be solved in isolation. Work with colleagues across chemistry, engineering, environmental science, and policy to develop well-rounded solutions. Stay curious and open-minded; some of the most impact ful innovations arise at the intersections of disciplines. And remember, research impact extends beyond publications— strive to connect your work to industry needs, community benefits, and global priorities such as food security and envi ronmental sustainability. By doing so, you will ensure your con tributions make a meaningful and lasting difference. ACI/CFAA GLYERCINE INNOVATION AWARDEE Thomas H. Epps III is the Allan & Myra Ferguson Distinguished Professor of Chemical & Biomolecular Engineering, Director of the Center for Research in Soft Matter & Polymers and Center for Hybrid, Active, & Responsive Materials, and Deputy Director, Center for Plastics Innovation at the University of Delaware in Newark. INFORM: Can you share your journey into the area of waste valorization for generating sustainable chemicals and polymeric materials? What inspired you to pursue this path? Epps: My journey into polymers began when I worked on poly mer films as a young student at NASA-Langley. I continued my polymer-related activities through undergraduate research in the Paula Hammond Lab at MIT and then moved to graduate research in the Frank Bates Lab at the University of Minnesota,

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mercial incumbents. This effort led to a patent and published work in ACS Central Science in 2018: “From tree to tape: Direct synthesis of pressure sensitive adhesives from depolymerized raw lignocellulosic biomass.” The second effort is our work that leveraged a new pro cess-intensification strategy enabled by glycerine that led to the simultaneous deconstruction (through liquid hydro gen donation) and separation of lignin-rich feedstocks, such as technical lignin. This process, called reactive distilla tion—reductive catalytic deconstruction (RD-RCD), elimi nated the need for high reaction pressures and hydrogen gas, and it enabled the design of a continuous and scal able process that ultimately nucleated a startup company, Lignolix, which is focused on the valorization of biomass feedstocks. Moreover, the utility of the process was demon strated through the generation of biobased 3D-printing res ins as explained in a patent and published work in Science Advances in 2022: “Ambient-pressure lignin valorization to high-performance polymers by intensified reductive cata lytic deconstruction.” Each of the efforts has led to follow-on work examining technoeconomic analysis (TEA) and life-cycle assessment (LCA) impacts, feedstock-structure-property relationships, and the examination of additional under-utilized sources of lignin-rich waste. INFORM: What are some of the biggest challenges you have faced in your research, and how did you overcome them? Epps: One of the biggest challenges that we face in our biobased feedstock-to-materials research is the complexity of the problem. Essentially, there is a strong interdependence between the choice of feedstock, its location, the process used for its deconstruction and purification, the resulting chemical/ material composition and properties, and the ultimate poten tial applications. We were very fortunate to participate in the National Science Foundation’s Growing Convergence Research (GCR) program, which allowed us to bring together a team of researchers spanning ecohydrology, polymer science, engi neering and catalysis, TEA and LCA, biomolecular engineering, and animal and food science. Through this highly collabora tive and multidisciplinary team, we developed a systematic framework to break down this complex valorization problem into ‘bite-size’ chunks so that we could make substantial fun damental science progress, while simultaneously being able to address the big-picture issues. Moreover, the GCR activities led to new international and industrial collaborations, as well as the launching of a startup company (Lignolix), to tackle specific challenges in biomass valorization. As a final note on this question, the framework

that we developed as part of the GCR has greatly informed our new efforts in plastics waste valorization, for which the chal lenges and opportunities are equally as complex – through our Center for Plastics Innovation (a Department of Energy, Energy Frontier Research Center) and adjacent activities. INFORM: How has your research evolved over the years, and what emerging trends do you see that excite you? Epps: When we began exploring lignin-derivable materials, our focus was primarily on understanding the structure and proper ties of polymers from lignin deconstruction products, without considering feedstock sourcing, life-cycle and economic implica tions, scale-up opportunities, or end-use applications. Over the past 13+ years, we have begun incorporating TEA and LCA into our basic science, using that knowledge to identify both funda mental and translational gaps. We have strengthened existing collaborations and established new ones, allowing us to use our structure–property–processing knowledge to develop mate rials and intellectual property that advance sustainability and resource security goals, while also improving performance. Going forward, we are particularly excited by advances in materials synthesis, reactor design (toward electrification, intensification, and modularity), and the growing emphasis on holistic life-cycle impact evaluation. INFORM: What role do you see AOCS playing in fos tering collaboration among scientists and industry professionals? Epps: AOCS is in a wonderful position to continue facilitating collaborations between academia and industry. The Annual Meeting session topics and session organization around indus try-relevant, yet fundamentally accessible, topics bridge the gap between the academy and industry allowing each group ample space to present exciting breakthroughs and highlight critical challenges to advance technology and society. This pairing fosters robust and sustainable post-session interactions from which I have personally benefited. INFORM: What advice would you give to young scientists and researchers? Epps: I would advise young scientists and researchers to fol low their passions and find a subject that genuinely interests them—something that sparks innate curiosity. That curios ity will lead to countless opportunities to ask questions, form hypotheses, and seek answers. As part of that process, learn from everything—every interaction, every seminar (even if it seems off-topic), every experiment. As someone once told me, the only experiment that is not worthwhile is the one you do not learn anything from. Finally, collaboration is key. Leverage your skillset to make an impact but also recognize when collab oration can multiply that impact.

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• Rice • Soybean • Sugarbeet

Visit aocs.org/crm to learn more about our CRM catalog.

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Gobs of glycerol: How a waste product could be George Hale

a sustainable

building block

For decades now, biodiesel has been touted as a way to decrease humanity’s reliance on limited fossil fuel resources and reduce greenhouse gas emissions. Each year, biodiesel producers convert vegetable oil, animal fat and waste fats like cooking oil into fuel that is then distributed around the world. However, these same producers have been facing a growing problem of what to do with a major co-product of making biodiesel, glycerol. In its pure form glycerol is a highly useful chemical. But glycerol pro duced when making biodiesel contains contaminants that make it unsuit able for use. Glycerol can be purified, but at a high cost in time, money and energy. This means that only the largest producers are able to do anything with it. At the same time, the sheer volume of glycerol created each year during biodiesel production has driven prices to record lows, causing a major oversupply. This has motivated researchers to find ways to valorize crude glyc erol from biodiesel production. Finding ways to convert contaminated glycerol into useful value-added products with little or no pretreatment would open up new markets for this resource. This would give biodiesel producers a new revenue stream and help make biodiesel production more economical. FROM FIELD TO FUEL TANK Biodiesel has long been on the market as an alternative to conventional diesel derived from petroleum. In some cases biodiesel is sold in its pure form, but most often it is available blended with petroleum diesel. For

• Biodiesel production generates large amounts of crude glycerol, a contaminated byproduct that is costly to purify and often treated as waste. • Researchers are developing chemical and biological methods to convert crude glycerol into valuable products like plastics, fuels, and industrial chemicals. • Contaminants such as methanol, salts, and unreacted lipids hinder these processes, but advances in catalysts and microbial engineering are making progress toward overcoming them. • Successfully valorizing crude glycerol could create new revenue streams for biodiesel producers, reduce reliance on fossil fuels, and make biodiesel more sustainable.

BYPRODUCTS

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instance, blends of fuel containing 5 to 20 percent biodiesel are common. Because biodiesel is derived from non-fossil fuel sources, it is sometimes considered a carbon neutral fuel. This, and its ability to reduce use of petroleum resources, attracted the attention of policymakers in the United States and Europe, who started requiring use of biodiesel in the early 2000s. For instance, the European Union once set a target of having seven percent of diesel sold be biodiesel by 2015. Similarly, Brazil expanded the use of biodiesel derived from soybean oil. While conventional diesel is made by refining petroleum, biodiesel is produced using a variety of lipids like vegetable oil. Producers use a chemical process known as transesterifica

tion, reacting lipids with alcohol in the presence of a catalyst like sodium hydroxide. This reaction combines one oil molecule and three molecules of methanol to produce three fatty acid methyl ester molecules, in other words biodiesel, and one mole cule of glycerol. Producers then separate the resulting biodiesel and glycerol and further refine the fuel, leaving crude glycerol behind. But with about 10 percent of the mixture by weight being glycerol, there is a lot of it left over. Some estimates have somewhere between 65 and 75 percent of crude glycerol being treated as waste, largely due to economic factors. This is because glycerol made during biodiesel production has a purity of around 60 to 80 percent at most, with it being

Mixed methyl esters (Biodiesel)

O

O

O

H 3 C-O

R1

O

NaOH CH 3 OH

H 3 C-O

R1

O O O O O

R2

H 3 C-O

R3

R2

Transesterification

R3

OH OH OH

Triacylglycerol

Glycerol

The alkaline catalyzed transesterification reaction in the formation of biodiesel from triacylglycerols (TAGs) (R1, R2 and R3 correspond to unique fatty acids attached to the glycerol backbone of the TAG or alkyl ester). Source: Ashby, et al. , JAOCS , 88, 7, 2011.

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Possible reaction mechanism for glycerol oxidation over an Au/Al 2 O 3 catalyst. FA, formic acid; GA, glyceric acid; GCA, glycolic acid; LA, lactic acid. Source: Chida, et al. , JAOCS , 97, 12, 2020.

lower in some cases. Crude glycerol is a mixture of pure glycerol and other chemicals from the transesterification process. This includes water, left over methanol, dissolved material from the catalyst and non-glycerol organic matter, commonly referred to as MONG, consisting mostly of lipids that did not react during the transesterification process. These impurities make it eco nomically infeasible for producers to sell crude glycerol. To counter this, larger biodiesel producers will take steps to purify crude glycerol. They will use distillation processes to remove water and excess methanol and filter out MONG and other chemicals like salts and sulfur compounds. This can get crude glycerol up to a purity of 95 to 99.5 percent, mak ing it more attractive to the market. However, contaminant levels vary from batch to batch depending on reaction condi tions and the lipid feedstocks used. For example, crude glyc erol made from pure vegetable oil will be notably different from a batch produced from waste cooking oil. Additionally, these purification steps add costs in the form of equipment and energy, putting them out of the reach of smaller biodiesel producers. CHEMICAL WITH A THOUSAND FACES Glycerol is a simple molecule made of a chain of three carbon atoms, each bonded to a hydroxyl group. Its structure and com position makes glycerol water soluble and hygroscopic. Glycerol is also non-toxic to humans and the environment. This has made it attractive for use in food, pharmaceuticals and cosmetic prod ucts. Additionally, glycerol can be used to supplement animal feed or as fertilizers. In the past most of the glycerol used in this way came from petroleum sources, but greener sources like purified crude glycerol have been gaining ground.

Although glycerol itself is extremely useful, its potential as building blocks for other chemicals is nearly limitless. As with its useful physical characteristics, this comes down to the mol ecule’s chemical structure. One of the carbon bonds in glyc erol is relatively weak. This means the molecule can be broken apart relatively easily and recombined into other chemicals ranging from artificial sweeteners to a variety of useful acids to monomers and polymers crucial for plastic production. “Glycerol is a very versatile molecule,” said Mickael Capron, professor of chemistry at the University of Lille in Lille, France. “You can do a lot of things with it.” Chemists can remix the carbon, oxygen and hydrogen atoms in glycerol with many different chemical processes. For instance, you can use oxidation to produce lactic acid, dehy dration to make acrolein, hydrogenation to convert glycerol into 1,3-propanediol, a chemical heavily used in plastics pro duction, and pyrolysis to make aromatics like benzene that are useful as fuel additives. The choice of process is driven by the desired end product. “It depends really on the products you want to target,” said Capron. Recently, researchers have been looking into new ways to convert glycerol into fuels like propane. Researchers at Aston University in Birmingham, England recently developed a two stage process where they first generated hydrogen gas from glycerol, which they used in the second stage to produce pro pane. In many cases the hydrogen used in chemical synthe sis comes from fossil fuel sources, making this an important development. “Producing renewable hydrogen is a very important energy vector and a high-demand chemical intermediate in

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modern society,” said Mohamed El Doukkali, associate profes sor of chemistry at the University of Sultan Moulay Slimane in Morocco and 2024 recipient of the American Cleaning Institute and National Biodiesel Board Glycerine Innovation Award. TO CLEAN OR NOT TO CLEAN Contaminants have been an obstacle to valorizing crude glyc erol, so researchers have been working to either find new, more cost-effective ways to purify it or explore how to use it without purification. The question, Capron said, is whether we have to use pure glycerol or can we use crude glycerol. The first step toward answering this is to better understand how different contaminants affect valorization processes. Capron and his colleagues took steps toward this goal by comparing conversion of pure glycerol and crude glycerol. They found that crude glycerol yielded about half as much end product as the pure form. Next they took pure glycerol and added impurities one at a time and quickly found that MONG was the culprit. “You no longer had access to the active sites,” said Capron. MONG was attaching itself to active sites on their cat alyst, rendering it ineffective. They found that cleaning the catalyst with a solvent after it started losing efficacy would restore it to its original state. However, they also looked into possible ways to make cata lysts that would be less affected by contaminants like MONG. The choice of catalyst material and structure depends heav ily on the desired end product as that determines the type of reaction and reaction conditions used. For example, pyrolysis of glycerol typically runs at 250–300°C and relies on catalysts based on zeolite crystals. Other processes make use of cata lysts made with metals like silver, gold, platinum, palladium or nickel, often deposited on scaffolds of alumina or silica. Capron and colleagues tested catalysts made with different metals and found notable differences in their selectivity and resistance to contaminants. They found that both gold and platinum were highly sensitive to impurities, while silver and palladium were both selective to their target chemicals and more resistant to MONG. PRODUCING PROPYLENE One major area of research into glycerol transformations is in the production of propylene, a simple hydrocarbon used exten sively in plastic manufacturing. With the rapid and accelerating growth in consumer electronic devices, demand for plastics and its precursors like propylene has taken off. However, propylene is typically made from petroleum and the available supply does not always meet demand. Shortages in propylene and fluctua tions in price are making a new and reliable source of the mate rial highly attractive. At the same time there is a growing call for plastic manufacturing that does not rely on fossil fuels and has no carbon dioxide emissions. While other methods like pyrolysis of industrial and urban waste exist, converting crude glycerol to propylene appears to hold promise. There are several methods for converting glycerol into propylene. Steam reforming is one method where carbon and hydrogen bonds are broken apart. The first step is used to

BIOFUEL PRODUCTION

BIODIESEL

EXCESS CRUDE GLYCEROL

BIOTRANSFORMATION

Glycerol

Microbial cells

Value-added compounds

GREENER AND MORE SUSTAINABLE SOLUTION

Source: Wang, et al. , Int J Bio Mac , 261, 129536, 2024.

producer hydrogen or syngas, a mixture of hydrogen and car bon monoxide. Carbon and hydrogen can then be reformed to glycerol. An alternative method that uses an inert atmo sphere rather than steam yields ethylene and smaller amounts of propylene. Both of these processes rely on temperatures of 600-950°C and require bulky equipment, but steam reform ing can be easily integrated into existing petrochemical indus try facilities. Another method, aqueous phase reforming, uses lower temperatures and thus consumes less energy. Hydrodeoxygenation, which uses overlapping deoxygen ation and hydrogenation processes, is another method that El Doukkali and his colleagues are looking into that uses lower temperatures and would have a lower carbon footprint. “We also considered crucial aspects like minimizing costs, energy consumption and greenhouse gas emissions,” said El Doukkali. Whichever method is used, the key to success will be designing an optimal catalyst. As mentioned, many catalysts used in valorizing glycerol use metals like molybdenum, plat inum, palladium or nickel deposited on a scaffold made of a material like alumina or silica. Tweaking the materials used, how they are deposited, and the structure of a catalyst can heav ily influence the catalyst’s efficacy and durability. The goal is to design a catalyst that can work in milder conditions, reduc ing energy use and resisting degradation and the formation of a carbon-rich material known as coke. This material is produced when heating carbon in the absence of air and deposits on a cat alyst’s active sites, keeping them from working. One study found that modifying existing catalysts used in steam reforming can reduce the temperatures needed. Similarly, thoughtful designs could improve the performance and durability of catalysts used in hydrodeoxygenation of glycerol.

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USING LIVING FACTORIES While research into improved chemical processes and catalysts continues, other studies have been looking into the use of bio chemical processes to convert crude glycerol. Biotransformation methods like fermentation take advantage of the natural activ ities of microorganisms to produce value-added chemicals. Biotransformation with fungi like Aspergillus niger and bacteria like Klebsiella pneumoniae is already being used to make sugar alcohols like erythritol, glyceric acid and an extremely use ful monomer called 1,3-propanediol. This monomer is widely used to make a variety of plastics and most of it being produced today is made through biotransformation of glycerol. There is a large global market for 1,3-propanediol, having grown from $490 million in 2009 to $870 million in 2024. Being able to con vert surplus crude glycerol into such a chemical would be an economic boon for producers. However, as is the case with chemical transforma tions, contaminants in crude glycerol are often problem atic. Dissolved salts and residual methanol can neutralize the microorganisms used to convert glycerol. On the other hand, MONG could be beneficial in some cases as it could be an extra source of carbon. Biodiesel producers can selec tively remove methanol for use in future transesterification. Also, some researchers are looking into genetically modifying microbes to make them more resistant to contaminants in crude glycerol.

CIRCLING BACK As research into chemical and biological transformations contin ues, one thing is clear. Being able to tap into existing streams of crude glycerol and make value-added products is certainly appeal ing. While large biodiesel producers can purify their co-produced glycerol, smaller companies are sometimes left with no alter native but to burn their stockpiled glycerol to produce energy. Finding ways to make use of this supply of glycerol would be tre mendously valuable, giving biodiesel producers another revenue stream and making production more sustainable. “If you are not able to valorize it, you lose a lot of money for sure,” said Capon. Being able to turn what has long been considered essen tially waste into valuable products also aligns with what moti vated people to start making biodiesel in the first place. A large portion of the materials that could be made with crude glyc erol are currently derived from petroleum. Opening the pipe line of crude glycerol could reduce demand for dwindling fossil fuel resources. With improved processes, better catalysts and optimized biotransformations, there could one day be inte grated biorefineries that take vegetable oil, including waste cooking oils, and turn out not only fuel but valuable plastics and other chemicals that drive modern life. George Hale is a freelance science and technology writer based in Pearland, Texas. He can be contacted at halegr@gmail.com.

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Biomass pyrolysis: Liquid properties David C. Dayton

Wood vinegar, pyroligneous acid, liquid smoke, pyrolysis oil, bio-oil, biocrude—these are all names for the hydrocarbon-rich liquid pro duced from biomass pyrolysis. Like petroleum crude and other indus trial oils, it is a chemically complex, multicomponent mixture that is dark and free flowing with a wide molecular weight distribution and boiling range. Beyond that, there are few similarities between bio-oil (the term that will be used here) and other crude oils. Bio-oils already have a range of commercial uses, from energy production to food flavoring. As a renewable fuel, they can substitute for petroleum in boilers that gener ate steam for electricity and heat. In addition, certain chemical components of bio-oils are extracted and incorporated into foods, where they add the distinctive smoky taste found in marinades, barbecue sauces, cheeses, and processed meats such as bacon and sausage. Researchers are also exploring new applications for bio-oils, particularly in advanced biofuels and specialty bioproducts. Efforts are underway to adapt conventional refin ing methods so that bio-oils can be upgraded into drop-in fuels compatible with existing infrastructure. Their rich chemical diversity is opening additional possibilities, including the development of biocides, flame retardants, and even synthetic vanilla. BIOMASS PYROLYSIS Bio-oil results from the thermal decomposition of lignocellulosic material in the absence of oxygen. This process is known as biomass pyrolysis. Typical feedstocks include: wood and wood product residues, agricultural residues—corn stover, cereal straws, and pur pose grown or energy crops—miscanthus, switchgrass, poplar and eucalyptus. Pyrolysis products depend on the feedstock and process conditions, but consist pri marily of solids, liquids, and gases in various ratios. The solid, called char or biochar, is rich in carbon and contains ash material from the starting feedstock. Condensable vapors and aerosols produced during biomass pyrolysis can also be captured as bio-oil. The most abundant component of bio-oil is water, up to 35 weight percent. The water comes from two sources. The first is free water in the feedstock that gets vaporized. The second is referred to as “water of pyrolysis” that originates from the dehydration of cellulose and hemicellulose in biomass during pyrolysis.

• Bio-oil is a product of biomass thermal depolymerization. • Bio-oil is a complex, multicomponent mixture with a wide molecular weight distribution and boiling range. • The elemental composition of bio-oil resembles that of the original biomass. • Bio-oils tend to have high oxygen content, are acidic, and thermally unstable.

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Usually, a single-phase water emulsion in oil is produced but that emulsion can be easily broken if the water content is high enough. The organic phase contains less than 10 percent moisture whereas the aqueous phase is mostly water with dis solved light organic oxygenates. The most abundant perma nent gases produced during biomass pyrolysis are CO and CO 2 , with lesser amounts of methane, hydrogen and light hydrocar bons (ethane, ethylene, propane, propylene, and butanes). PYROLYSIS PARAMETERS Biomass pyrolysis can be considered slow or fast depending on the temperature, pressure and residence time to maximize products. Process temperatures are usually between 450 °C and 650 °C. For maximum biochar the recommendation is a slow pyrolysis process at lower temperature, higher pressure, and a long residence time (hours) performed in kilns or retorts. Maximizing liquid bio-oil yields requires a fast pyrolysis process using short vapor residence times (seconds) at temperatures up to 500 °C and atmospheric or sub-atmospheric pressure. Fast pyrolysis processes involve high heat transfer rates, on the order of 1000 °C per second, that result from injecting ambient temperature biomass into a high temperature reac tor for less than one second. Increasing the temperature up to 700 °C or higher in a fast pyrolysis process results in greater vapor cracking and higher pyrolysis gas production. BIO-MASS COMPOSITION In general, if it is in the feedstock it will end up in the bio-oil. There are many databases available that contain large librar ies of biomass elemental and chemical compositions. The average elemental composition of biomass is 51 weight per cent carbon, 41 weight percent oxygen, 6 weight percent hydrogen with a balance of nitrogen and sulfur (https://doi. org/10.1016/j.fuel.2009.10.022). The largest variation in the biomass elemental composition is in the sulfur and nitrogen contents, but they are present in low concentrations that can be significant depending on the bio-oil application. Most biomass is 25 percent lignin and 75 percent carbo hydrate, a combination of cellulose and hemicellulose. Woody biomass tends to have higher lignin content than herbaceous biomass (grasses, stover, and straws) and certain biomass, like softwood, can have a high extractives content. Extractives include materials like waxes, fatty acids, resins, gums, and tannins. Another highly variable component of biomass is the ash content. For most debarked woody biomass, the ash content is less than 1 weight percent while feedstocks like rice straw or rice hulls can contain up to 20 weight percent ash. While ash has little impact on the pyrolysis process, some ash com ponents act as catalysts promoting char formation or vapor cracking. Green wood can be up to 50 weight percent water but thermochemical biomass conversion processes include a dry ing step to control the moisture content of the feedstock. Feedstocks and process conditions do impact bio-oil characteristics and compositions, but in a non-selective way.

Technology developers use catalysts and reagents in the pro cess strategically to control a bio-oil’s physical properties and chemical composition. CATALYTIC FAST PYROLYSIS For catalytic fast pyrolysis, a technology developer uses cat alysts like zeolites, metal oxides, or solid acids to control the chemistry of the vapors and produce a higher quality bio-oil. Quality in this case is broadly defined as less acidic and more thermally stable. The catalysts promote deoxygenation of pyrolysis vapors by hydrodeoxygenation (removing oxygen as H 2 O), decarboxylation (removing oxygen as CO 2 ), and decar bonylation (removing oxygen as CO) to destroy acidic compo nents and increase the hydrocarbon content of the bio-oil. The goal is to improve the thermal stability of bio-oils for direct use or upgrade them to transportation fuels using conven tional petroleum refining technology like hydrotreating and hydrocracking. The various fast pyrolysis pathways are summarized below. Catalytic biomass pyrolysis processes can be performed in-situ if the biomass and catalyst are mixed directly in the primary conversion reactor or ex-situ if the pyrolysis vapors interact with the catalyst in a secondary downstream reactor. The in-situ process has the advantage of fewer reactors and a lower capital cost. The ex-situ process avoids potential catalyst poisoning by separating the biomass ash from the catalyst and provides increased flexibility with independent temperature control in each reactor. In addition to catalysts, reagents or gases act as another variable in the biomass pyrolysis process. Hydrogen is added most often. In combination with an appropriate catalyst, it enhances the hydrodeoxygenation pathway for pyrolysis vapor deoxygenation. Increasing the pressure of the catalytic fast pyrolysis process with hydrogen achieves almost complete deoxygenation. Each fast pyrolysis process has strengths and weak nesses, so selecting the appropriate pathway depends mainly on the downstream use of the bio-oil. Deoxygenation of bio mass pyrolysis vapors is useful for upgrading bio-oil to fuels. However, complete deoxygenation may be counterproductive if the intention is to isolate specific bio-based chemicals from

Fast Pyrolysis

Vapor Phase Upgrading

Fast Pyrolysis

Catalyst Added

Catalytic Fast Pyrolysis

Biomass + Heat

Bio-oil

H ₂ Added

Reactive Catalytic Fast Pyrolysis

High Pressure

Hydropyrolysis

Summary of pyrolysis pathways.

Other

Nitrogen Compounds

Phenols

PAH

Monoaromatic

Furan

Carbonyl

Aliphatic

Alcohol

Acid

100

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Summary of Bio-oil Properties

Property

Description

Oxygen Content

35–50%

Acidity (pH)

2–4

Functional Groups

Alcohols, acids, ketones, aldehydes, phenols

Stability

Poor; reactive, polymerizes on aging Partially water-soluble, polar Low (many heavy compounds)

Solubility Volatility

Sulfur/Nitrogen Content

Low (feedstock-dependent)

the bio-oil. Finally, whole fast pyrolysis bio-oil is effective as a fuel oil substitute without any upgrading. PHYSICAL PROPERTIES Bio-oils are dark, multicomponent mixtures with a distinctive smoky odor that flow freely. As the pyrolysis process condi tions and the feedstock composition affect the properties of bio-oils. But high water (15-30 weight percent) and oxygen (35-50 weight percent) content determine the physical prop erties of bio-oils. Consequently, the lower heating value (LHV) is much lower than other hydrocarbon liquids (in the range of 13-18 MJ/kg compared to 40-44 MJ/kg for gasoline and diesel) and the density of bio-oils is typically in the range of 1.1-1.3 g/ ml at ambient conditions. A fraction of the oxygenated species are organic acids, so bio-oils tend to be very acidic with a pH in the range of 2-4. Finally, the high oxygen content of bio-oils makes them immiscible with hydrocarbons like gasoline and diesel but miscible with oxygenates like alcohols and ketones. Bio-oil viscosity varies greatly (10–1000 centipoise at 40 °C) depending on the solids content, water content, and molecular weight distribution (specifically the oligomer con tent). But bio-oils are thermally unstable and continue to undergo chemical reactions even at mild storage and pro cessing conditions. Reactive components like aldehydes and ketones are prone to polymerization and increase viscosity. Condensation reactions combine two reactive components, like phenolics, to produce larger molecules that increase viscosity and more water that causes the bio-oil to phase separate. Initially, bio oil viscosity can be at the low end of the range, but the vis cosity increases slowly over time during storage (aging) or rapidly upon re-heating as the reactive components polym erize and potentially carbonize. Increasing temperature to reduce viscosity and improve the flow through an upgrading process may work for hydrocarbons but not for bio-oils. CHEMICAL PROPERTIES Bio-oils are also chemically complex mixtures with a broad molecular weight distribution and a wide boiling range. Researchers used gel permeation chromatography to mea sure the molecular weight distribution of bio-oils (https://doi.

org/10.1016/j.jaap.2024.106354). Roughly 50 percent of the bio-oil components are between 0-200 g/mole. Distillation studies showed that 25-50 volume percent of bio-oils boil above 300 °C (https://doi.org/10.1039/c6ra21134h) but the poor thermal stability of bio-oils can yield up to 20 vol percent of the starting material to form non-volatile residuals. Basic bio-oils contain light oxygenates, lignin-derived phe nolics, and carbohydrate-derived furans and sugars. Specific chemical components include alcohols, aldehydes, ketones, car boxylic acids, esters, phenolics, and anhydrosugars. Gas chro matography with mass spectrometric detection (GC/MS) is a common method for determining bio-oil chemical composition. The figure below shows the bio-oil chemical compositions that result from various feedstock chemical compositions pro duced from catalytic fast pyrolysis. Chemical composition mea sured by GC-MS identifies hundreds of unique compounds. Researchers determined the relative amounts of each com Fast Pyrolysis Fast Pyrolysis Vapor Phase Upgrading Catalytic Fast Pyrolysis Reactive Catalytic Fast Pyrolysis Hydropyrolysis Bio-oil Biomass + Heat Catalyst Added H ₂ Added High Pressure

Other

Nitrogen Compounds

Phenols

PAH

Monoaromatic

Furan

Carbonyl

Aliphatic

Alcohol

Acid

100 90 80 70 60 50 40 30 GC/MS Analysis (Area%)

20 10 0

Pine

MSW

Plastic

Biosolids

Corn stover

Miscanthus

Hybrid poplar

Chemical composition of bio-oils produced from various feedstocks determined by GS/MS analysis. Source: Wang, K., et al. , E Tech , 5(1), 183–188, 2017.