The development of biopolymers can substantially reduce marine and soil pollution
Do you think that if you throw a plastic food bag on the ground nothing can happen because you have only done it once? That it will “clean up” itself somehow? You can be sure that every single piece counts.
According to the Ellen MacArthur Foundation's report published last year, at least eight million tonnes of waste end up in the oceans every year. This is about one waste container a minute. One minute! What is worse, in 2030 it will be two containers per minute and four in 2050!
The same document states that in a business-as-usual scenario, by 2025 the oceans will contain one tonne of plastic per three tonnes of fish, and by 2050 the oceans are expected to contain more plastics than fish. Plus, plastics get into fish meat and through the meat into human bodies. Plastics also contaminate water. According to Orb Media’s research in the US, water was contaminated in 94% of the samples, including water in the Congress building, the Trump Tower in New York, and the Environmental Protection Agency.
But enough distressing news. There is no doubt that there is a need for a greener approach. The solution could be biopolymers or bioplastics, which break down in nature much faster. However, their production is expensive and producing bioplastics is roughly five times more expensive than conventional plastics made from non-renewable petroleum materials. This is due to the energy-saving and technologically more complicated production.
The scientists of the Polymer Institute Brno, in cooperation with UNP-RPA Litvínov, conduct research on suitable biomaterials for a reasonable price.
Do you think that if you throw a plastic food bag on the ground nothing can happen because you have only done it once? That it will “clean up” itself somehow?
What is the progress and what is the goal?
"At present, we have in place a strategic plan which aims to reduce the impact of hard-to-decompose petroleum-based plastics on the environment. We focus on producing bioplastics that could fulfil the primary function for which they are created, and to fully replace the currently used petroleum-based plastics," says Pavel Huljak of the Material Research Department at the Polymer Institute Brno.
Biopolymers, i.e. materials obtained from renewable sources, were known as early as the first half of the last century. These are natural polymers that are produced by a number of bacteria as a source of carbon and energy. To do this, however, they need a substance which they convert into polymers in a subsequent fermentation process.
The input substance, the "food for bacteria", is usually of organic plant origin, such as corn stalks, sugar cane, crushed grains, and other crops containing polysaccharides.
What is the difference between a common plastic and a biopolymer?
Common polyolefin plastics (polypropylene and polyethylene, for example) are made from non-renewable petroleum inputs and take very long to decompose, to the order of tens to hundreds of years. This results in an ever-increasing amount of solid waste which goes not only to landfills but also to oceans.
By contrast, bioplastics are easily biodegradable (biodegradation is the process of material degradation in nature) and decompose through natural aging in landfills within months.
A biopolymer synthesized by bacteria is isolated and a crude product is obtained, and altered according to its future function. At present, these materials are garnering attention as a result of the growing demands on ecology and waste management.
Which substances are natural polymers?
"They include, for example, polylactic acid, also known as polylactide, which is obtained by polymerizing lactic acid. This substance is naturally found in our body and is part of the daily diet for the majority of the population," says Pavel Huljak.
Other biopolymers are polyhydroxybutyrate, polycaprolactone, polyethylene glycol, and many others. These polymers are inspired by their natural analogues, biopolymers synthesized by nature, such as starches, cellulose, natural rubber, gelatine, and resin.
"We are only creating biopolymers in a way nature could not," adds Pavel Huljak.
The Polymer Institute Brno is trying to develop a suitable material that will be based on renewable resources, easily decomposable, and compostable. It is important for the material to naturally age in landfills without any side effects, such as emission of toxic products into the air, water or soil.
The main reason why producing biopolymers is a good thing is the reduction of the carbon footprint in the air, avoiding any increase in the concentration of carbon oxides in the production or combustion of conventional petroleum-based plastics. Ignoring these issues could only bring problems in the future with the well-known greenhouse effect and the deterioration in air quality.
Countering the benefits, the disadvantages of biomaterials are their generally high brittleness and stiffness (in terms of ductility and plasticity) as well as a high susceptibility to hydrolysis caused by absorption of air humidity.
"Based on these facts, we try to modify these biopolymers so that they can be used in areas in which such properties are undesirable and limiting," says Huljak.
Where can biopolymers be used?
Their advantageous feature is biocompatibility and biosafety.
For this reason, they are frequently used in medicine, for example as a shelf-life drug carrier, or so-called scaffolds, which serve as a temporary substitute for damaged tissue to which appropriate stem cells are applied. After a given time, the biopolymer breaks down inside the human body and it is excreted in the usual way. However, biomaterials are no longer needed at this stage, as the applied cells themselves infiltrate the damaged tissue by proliferation in the scaffold and the tissue is regenerated.
It is also possible to use biomaterials as hydration sheets in the form of hydrogel for treating burns.
These properties may also advantageously be used in the food industry as packaging materials. These include plastic bottles, cups, bags, foils, tea bags, and the like. Here, a great emphasis is placed on the release and extraction of potentially hazardous and toxic substances originating from natural aging, even during longer storage periods.
However, this risk is very low for biopolymers. They are made of natural material; therefore, they are not degraded to anything other than the substances that are already part of our body or a part of our diet.
Can a biopolymer be released into food, which is a frequently discussed topic when it comes to common plastics? "For example, for a packaging material made from polylactic acid, the amount of lactic acid released into food is about 700 times lower than the daily intake of this acid in a breastfed infant in the form of human milk," says Pavel Huljak.
Biopolymers are also used in the preparation of biodegradable films under crops. They release water very well and irrigate plants, and after a certain time when they are no longer needed they break down and naturally integrate into the soil ecosystem.
They are used as packaging materials in cosmetics and consumer products such as shampoo bottles and creams.