Can Plastic Go Green?

Researchers at TalTech in Estonia push to produce biodegradable packaging from cellulose

Pressure is building to find greener alternatives to plastic food packaging. While millions of tonnes of almost indestructible plastic enter the world’s oceans each year, malleable packing films are burned or sent to landfill after use, causing further pollution.

In an ideal world, the oil-based polymers used to pack food and drink would be swapped out for bio-based polymers that will quickly degrade without causing any harm to the natural environment. Andres Krumme, a professor in the Department of Materials and Environmental Technology, Tallinn University of Technology (TalTech) in Estonia, is trying to make that happen. “All of mankind is looking for a substitute for oil-based polymers,” he says. “Today, we are packing everything, including food, in polymers that can have a useful lifetime of 10 to 60 years.”

In their labs, Krumme’s research team has successfully developed a new type of cellulose-based polymers that can be melted and manipulated in the same way as low density polyethylene (a widely used packaging material), under conditions similar to those typically used in industrial polymer processing. “Cellulose biopolymer is generally highly crystallized with strong hydrogen bonds, which means it can’t easily be melted or processed,” explains Krumme. “But our new polymers – cellulose fatty acid esters– can be processed in the same way as the commodity polymers.” Moreover, he says the relatively easy modification procedure should make it possible to obtain other new polymers with a wide range of properties.

The most abundant polymer in the biosphere

As cellulose is the main constituent in the cell walls of all plants, these new polymers could be sourced from trees, algae and other vegetation grown on land that isn’t being used for agriculture. “Cellulose is the most abundant polymer in the biosphere,” notes Krumme. “If we could harness 0.4% of the cellulose produced in the biosphere we could replace all the plastic produced each year across all sectors – 350 million tonnes annually.” Today, bio-based polymers are produced at scale. But they are generally sourced from crops, cultivated with pesticides and fertilisers on land that could be farmed for food. As the global population rises inexorably, this approach may no longer be sustainable. In northern European countries, such as Estonia, agricultural land is limited, but forest cover is plentiful.

Another attractive feature of the new polymers Krumme is developing is they can be adjusted for various levels of permeability, he explains: “It can be a quite good barrier material – better than polyethylene. One can also adjust the ratio of biodegradability according to the useful lifetime of the packaging, which could be months, weeks or days.”

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