Whether you like them or not, eggs, cheese, mushrooms or shrimp are likely to be part of your future shopping basket—as the raw materials in a new kind of plastic packaging.
New materials promise not only to reduce our reliance on petroleum products such as plastic, they also cut waste. Packaging accounted for more than 75 million tons (or 30%) of solid waste in the U.S. in 2013, while the European Union generates around 79 million tons of packaging waste annually.
However, waste from the agriculture industry is now being turned into biodegradable packaging materials. For example, Kirsi S. Mikkonen, a researcher at the University of Helsinki, is developing packaging films made from hemicelluloses, byproducts of the forestry industry and agriculture.
Cellulose, the part used by industry, makes up only 40% to 50% of wood, while hemicellulose and lignin each account for about 30%. Hemicelluloses can be retrieved from wood chips or, in thermo-mechanical mills, from wastewater.
Dr. Mikkonen converts the hemicelluloses into films that act as an effective barrier against oxygen. Edible films could protect food from drying out or spoiling, or even within food, to separate pizza crust from sauce. By coating paperboard with the films, she can make plastic-type containers.
Hemicelluloses and lignin can also be used in aerogels, which are porous and light but strong.
“When you put an aerogel in water, it acts like a sponge,” Dr. Mikkonen says. “It absorbs water and you can press it out, and it recovers its shape. We could make something like a soft pillow that could absorb moisture or drips from meat, or it could release active compounds and be used as active packaging.”
Innovations in active packaging abound. The Fraunhofer Research Institution for Modular Solid State Technologies in Munich has developed a sensor film that detects molecules called amines that are released when meat or fish starts to spoil. As amines build up, the sensors turn from yellow to blue, indicating the level of spoilage. Many companies now sell labels and films that keep fruits and vegetables fresh by absorbing ethlyene.
Egg whites could provide another form of active packaging. Alexander Jones, a researcher at the University of Georgia in Athens, Georgia, mixed the egg-white protein albumin with glycerol to create a plastic with antibacterial properties.
Albumin plastic could be used for food packaging, to decrease spoilage. It could also be mixed with conventional plastic to add antibacterial properties to medical products, says Suraj Sharma, associate professor at the University of Georgia’s College of Family and Consumer Sciences.
Another reason to mix in conventional plastic is that albumin plastic is too brittle to be used alone for, say, a catheter tube, which needs flexibility, Dr. Jones says.
He also tested plastics made from soy and whey proteins. Soy proteins had no antibacterial properties—“it actually fed bacteria,” he says. Whey proteins mixed with glycerol made antibacterial plastic, but whey plastic minus glycerol acted like soy-based plastic, promoting bacteria growth.
The protein-based plastics have other advantages. They compost quickly, and the manufacturing process uses lower temperatures than for petroleum-based plastics, thereby saving energy. Whey, a byproduct of cheese processing, requires treatment before disposal, so diverting it into plastics would be a boon.
For now, egg whites are far more expensive than polyethelyne. But Dr. Jones believes that we might tap waste streams to get cheaper raw materials.
“Egg producers have eggs they don’t ship for various reasons,” Dr. Jones says. Using those “would reduce waste and also not compete with food as an end use.”
Shrimp shells are another waste source that can be turned into plastic. Harvard University researchers have turned chitin, a polysaccharide found in crustacean shells, into a strong, transparent material called shrilk, which can be used to make plastic bags, packaging and even diapers.
Meanwhile, Ecovative, a packaging company in Green Island, N.Y., uses mushrooms as the key ingredient in its compostable packaging. The root structure of a mushroom, called mycelium, acts like a glue. A mix of mycelium and agricultural byproducts is molded into different shapes, replacing styrofoam for example.
“Packaging today is essential for society to function,” Dr. Mikkonen says. “We need packaging to deliver food from the maker to the retailer and then to the consumer. But it produces lots of waste. It’s really important to develop some biodegradable alternatives.”
This article was originally posted on 3D PERSPECTIVES.
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