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- Sugar beet pulp is mixed with melted polylactic acid and passed through a twin-screw extruder. This results in pastalike strands (the brownish solid tubes coming out of the front of the machine) of composite material, which are then cooled, chopped into pellets, and injection molded. Photo courtesy of ARS.
This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from USDA's rich science and research profile.
Valentine’s Day has come and gone, but the scientists of USDA’s Agricultural Research Service (ARS) still have some sweet news to share: In a classic case of turning trash into treasure, they’ve created a biodegradable plastic made from sugar beet pulp.
Using a process called extrusion, the ARS scientists combined sugar beet pulp, the leftovers from turning sugar beets—the principal source of American sugar—with a commercially available biodegradable polymer called polylactic acid (PLA) to create a new “thermoplastic,” a plastic that becomes soft when heated. Extrusion is already used widely in large-scale production of food, plastics and composite materials, and it’s very cost-effective.
The scientists say we could use this new thermpolastic to make those soft, white, spongy containers that are a perfect holder for a burger and fries (especially with the top flipped open to hold the fries).
America’s sugar industry piles up 1 million tons annually of the leftover beet pulp, so there’s no shortage of that ingredient for the new product. The PLA can be made from sugars in corn, sugarcane, switchgrass and other renewable feedstocks. The ARS scientists say you can use up to 50 percent sugar beet pulp in the thermoplastic mixture and still get a finished product with properties similar to those of polystyrene and polypropylene, the compounds now used to make food containers.
That’s not all: The scientists can combine the sugar beet pulp with water or glycerol to create a different type of thermoplastic that could find a new life as yogurt cups, cottage cheese tubs, and bags. In that formulation, the recipe could be up to 98 percent sugar beet pulp.
That translates to good news for sugar beet producers and beet sugar processors who would have a market for the leftover pulp, and sweet news for environmentally conscious consumers and Mother Earth herself!