Almond shells as an ingredient in plastics

The Institute of Food Technologists show held in Chicago mid-July centers on food ingredients and processing flavored with a little packaging. Intriguingly, a Tech Theater presentation sponsored by the Almond Board of California (Modesto, CA) disclosed research and development in using almond shells as an ingredient in plastics for applications including packaging.

Nutty idea? Literally it is, but figuratively it’s not—the shells enhance the plastics’ strength beyond most traditional materials. The shells are being tested as a partial plastic replacement in plastic trays and pallets and other containers and products.
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The highly “edutaining” presenter was Bill Orts, research leader, Bioproducts, Western Regional Research Center (Albany, CA) of the United States Department of Agriculture, who responds to PlasticsToday’s questions. Orts credits much of the answers to Zach McCaffrey, almond project research leader, and Lennard Torres, who he describes as “our polymer go-to-guy.”

Let’s start with an overview of your group.


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Orts: The team has been working on sustainable agricultural-derived plastics for at least 20 years with a scope well beyond fillers. We’ve quietly worked with companies like EarthShell, Cargill-Dow (Ingeo), Clorox-Glad, Metabolix, etc., to create sustainable packaging solutions.

We’ve also been actively involved in creating standards for the industry. My colleague, Greg Glenn, and I have been on multiple standard committees to help establish, for example, ASTM D6400, ASTM D6868 and the USDA Biopreferred Program. Both Greg and I have been active officers in Bioenvironmental Engineering Polymer Society and the Biodegradable Products Institute (New York City)

We help companies in this area on a regular basis, and those include these Strategic commercial partners that are presently located within the Research Unit (pilot plant) among others: Method Products (San Francisco), provides us with several researchers to develop sustainable packaging solutions for detergents and other products; tire company Bridgestone Americas Inc. (Nashville, TN) collaboration that provided a big grant to make domestic rubber and another big grant from Cooper Tire & Rubber (Findlay, OH) to make greener tires.

In a nutshell, what’s this research all about as it relates to plastics?

Orts: California produces more than 80% of the world’s almonds. That leads to the problem that almond growers and shellers must find an outlet for more than one billion poundsAlmond parts diagram of shells every year. Using shells as fillers in polymer composites have multiple advantages over commercial additives, e.g., cost, energy consumption, renewability, biodegradability, landfilling; however, almond shells are hydrophilic, which limits their incorporation into most polymer matrices. Our research is investigating using almond shells as a filler in polymer composites and results have shown we can make stiffer, stronger and more heat-resistant composites compared to the unfilled polymer. We’re starting to work with industrial companies to optimize materials to meet their specifications and work towards scaling up.

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The process involves torrefication—what exactly is that?

Orts: Torrefaction is a thermal process where biomass is heated to 200-300 ⁰C in the absence of air and oxygen. Compared to raw biomass, torrefied biomass is more hydrophobic, making it more chemically compatible with polymer matrix, and more grindable, reducing the energy required to mill to a small particle size.

Torrefied shells are used as filler and strengthener…what materials do the shells replace?

Orts: Common industrial fillers include calcium carbonate, talc and carbon black.