In the 19th and 20th centuries, small hydrocarbons produced from the excavated fossil fuels were polymerized to create polymers, most commonly polypropylene, colloquially known as plastics.
The plastics have unrivaled properties, including but not limited to high durability, resistance, light-weight, and can be easily processed. Due to the availability of different hydrocarbons, different polymers with variable properties can be synthesized. The versatile properties of petroleum-derived synthetic plastics have been utilized to make human life comfortable. Furthermore, the plastics are commercially produced at a very low price of US$ 0.70-1.0 per kg, which makes them highly popular among consumers.
Plastics have a wide spectrum of unrivaled properties that have improved modern lifestyles with their ever-growing applications in packaging materials for home appliances, aerospace materials, and biomedical instrumentation and devices. No other polymer can compete with the exceptionally desirable properties of plastics.
The key problem
Due to the cheap cost of production, the majority of plastic is discarded after a single-use. Plastics have an inherent property of microbial resistance, making them non-biodegradable. These low-grade single-use plastics have become an environmental nuisance by causing severe waste management issues and choking hazards. In the environment, plastic can last for thousands of years without degrading. What would have happened if plastic production started a thousand years ago? Scary, isn’t it?
Since their uninhibited production has already spanned for 150 years, the severity of the environmental issues has left us speechless. Plastic disposal in land and water has caused choking hazards in terrestrial and marine ecosystems. The burning of plastic waste leads to the production of poisonous gases, which eventually cause air pollution, which can cause respiratory disorders in animals.
The best solution is to discard the use of plastic. However, it is easier said than done. The wide applications of plastics and lack of suitable replacements have made us rely exclusively on plastics. Therefore, various strategies are being implemented to reduce the utilization of plastics; however, the results have been sub-par.
Re-use and Recycling
The catchy mantra of the 3 ‘R’s – Reduce, re-use, and recycle has been around for a while already, but the effect of these strategies has not been very eye-catching. They are almost incompetent for completely eliminating the use of plastics. Therefore, the global rate of plastic production is much higher than their recycling rate. Moreover, the process is rendered useless due to several chemical additives like pigments, coatings, and fillers that obstruct their processing.
Alternatives to plastics
In the 21st century, there has been a constant to identify polymers that can replace plastic. These polymers should have properties similar to that of plastic, and at the same time, they should be biodegradable. The efforts were paid off after the discovery of few such polymers like PLA (Polylactic acid), PHAs (Polyhydroxyalkanoates), which can be classified as:
Chemically synthesized polymers
Polymers such as PLAs (Polylactic acid), Polyglycolic acid, etc., are included in this category. The monomers like Lactic acid require lactic acid produced from cultivated crops which can then be polymerized in PLA. These polymers can degrade upon specific microbial or enzymatic hydrolysis and are considered as ‘conditionally biodegradable.’
This category includes blending of polymers and starch such as Starch-Polyethylene. The starch can be degraded by micro-organisms makes the polymer blend susceptible to microbial degradation. This increases the rate of polymer degradation.
PHAs – Polyhydroxyalkanoates
They are polyesters formed from butyric acid and can eventually degrade completely to produce water and carbon dioxide. These polymers are produced by various microbes by converting food sources like glucose, fructose, etc., into PHA. Their properties are similar to that of plastics which makes them an ideal substitute for their replacement.
Technology advancement is extremely necessary to convert end-of-life plastics into valuable feedstock. The technology needs to transit from the non-degradable single-use plastic to newer biodegradable materials to ensure ecological sustainability.