Researchers at the U.S. Department of Agriculture have been developing strategies to improve sustainability of single-use items and building materials, recognizing that developing new uses for under-valued coproducts from agriculture would be an important economic driver for growers and manufacturers. A wide range of often starch-based bioproducts are been pushed toward commercial application, with uses as home care products, building insulation, fire-retardants, and single-use food service items, such as clamshells, plates and degradable utensils. This report will mainly focus on development of single-use foam composites to be used as interior packaging that insulate and protect items during shipment. Synthetic packaging has come under increasing scrutiny due to the volume sent to landfills and their negative impact on the environment. We describe here a novel approach that combines the insulative properties of cellulose fiber foams with a starch binder and different three different reinforcing paperboard elements (angular, cylindrical, and grid) to make low-density foam composites with excellent mechanical strength. Resulting foams and composites had a consistent thickness and a smooth, flat finish, as well as low density (~65 kg/m³) and low thermal conductivity (0.039 to 0.049 W/mk). The addition of starch to the fiber foam composites dramatically increased the mechanical strength, while adding paperboard increased flexibility. Specifically, starch-fiber foams with paperboard composites had 240% and 350% higher average flexural strength (σfM) and modulus (Ef), respectively, than the original fiber mat. Results from other similar composite-forming technologies will be presented, including the role of torrefying fibril additives to change mechanical and thermal properties of composites. Torrefaction is heat-treatment of fibrils to 200-300^oC in limited oxygen to create “torrefied” fibrils and nanoparticles. Torrefied fibrils from walnut or almond shells (TAS), when used as a partial replacement for petroleum-derived carbon black fillers in polymer matrices, improved heat stability (the heat deflection temperature) by as much as 10 ^oC, thus improving marketability. Respirometry results will be presented to describe the biodegradation rate of these materials, highlighting their benign environmental impact.

Zach McCaffrey

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