The idea of a “biodegradable” plastic suggests looking at a material as similar as conventional plastic and not to confuse it with other substitutes. A biodegradable plastic is a material that can degrade to little or nothing over the years to come, posing minimal threat to the environment as well as wildlife. Moreover, these biodegradable plastics are still made from petrochemicals, however, they are engineered to biodegrade by breaking down at a faster pace under suitable conditions.

Biodegradable plastics are naturally decomposed in the environment over a period by the action of microorganisms that metabolize and further breakdown their structure. The resulting material is the one which is less harmful to the environment when compared to conventional plastics.

The truth is that these plastics are not as landfill friendly as they claim to be, but their benefits may outweigh the negatives because they degrade much faster than conventional plastics, especially when they are manufactured using the right materials. Unfortunately, the complications associated with biodegradable plastics does not end here. The reality is that they are made from petrochemicals, which means the residue they leave behind might be toxic. Owing to these reasons, the biodegradable plastics are often difficult to compost off.

Unquestionably, plastic is one of the world's most versatile material —from cars to food wrap and from planes to pens, anything and everything can be made using plastic. But there's a snag, getting rid of plastics is extremely difficult as plastics don't mix well with nature as they are synthetically prepared and does not belong to our world. Discarding plastics or burning them causes pollution, releases toxic chemicals, choking birds, killing fish, cluttering rivers, seas and thus harming our environment.

According to United Nations Environment Program (UNEP), it is estimated that nearly half of the amount of plastic produced ends up in either a landfill or in the natural environment. Regardless of all programs associated with recycling coupled with green mindedness, plastic seems to make its way to the trash.

HOW IS DEGRADABLE PLASTIC DIFFERENT FROM REGULAR PLASTIC?

Regular plastics hold carbon when they are formed. This carbon is released into the environment when these plastics begin to decompose or when they are melted. On the other hand, no carbon is released on burning biodegradable plastics because the manufacturing takes place without involvement of carbon. Along with this, gases like methane and other forms of pollutants is also released from conventional plastics which is not the case with biodegradable plastics.

Owing to these reasons, biodegradable plastics are advantageous to use over standard plastics, although these plastics are slightly costlier to produce but they have lesser environmental impact.

ENVIRONMENTAL BENEFITS

Microbial Degradation: The main aim of biodegradable plastic is to replace conventional plastic that exist in landfills and continues to degrade our environment, making at a less attractive place. Degradation or decomposition of these biodegradable plastics by microbial action is an incredible advantage to the environment. Break down of these plastics takes place in 3 steps that are colonization of the plastic surface, hydrolysis, and mineralization. It starts with microorganisms populating the exposed surface of plastic continued by secretion of enzymes by the bacteria that binds to polymer substrates or carbon source, ultimately splitting the hydrocarbon bonds. This process results in H2O and CO2 production. Here these biodegradable plastics leave a smaller CO2 footprint as compared to usual plastics, which is why they are looked towards as a viable replacement to traditional plastics as they cause less pollution when accumulated within landfills.

MAKING OF BIODEGRADABLE PLASTIC

Biodegradable plastics are made using all- natural plant materials such as orange peels, starch, corn oil, and plants. Unlike traditional plastic, biodegradable plastics are made from natural sources that does not contains any chemical fillers, thereby posing lesser risk to the environment contrary to regular plastics. 

The manufacturing process of biodegradable plastics begins with the melting down of all the materials. Then this melted mixture is poured into molds of numerous shapes like plastic water bottles and utensils.

Based on some evidences, it can be stated that plastic produced from plants has fewer negative impacts on the environment as compared to ones made from crude oil.

APPLICATIONS

TYPES OF BIODEGRADABLE PLASTIC

BIO-BASED PLASTICS

Bio based plastics, popularly known as bioplastics are biologically synthesized plastics that are produced from natural sources like plants, animals, or micro-organisms.

1.  Polyhydroxyalkanoates (PHAs)

This class of biodegradable plastics are produced from microorganisms (example: Cuprividus necator) by depriving them of certain nutrients and then supplying carbon sources in excess. Afterwards, the granules of PHA are recovered as soon as the micro-organisms are ruptured.

2.  Polylactic Acid (PLA)

 PLA is thermoplastic polyester which is produced from renewable biomass such as cassava, corn, sugarcane or sugar beet pulp, making it compostable but non-biodegradable because of its inefficiency to degrade outside of artificial composting conditions.

 3.  Starch Blends

 During the production of these thermoplastic polymers, plasticizers are added while blending the starch. This addition is important to augment its crystallization as the starch polymers are brittle at room temperature. While all the starches are biodegradable in nature, plasticizers are not. Therefore, the biodegradability of the starch blend is basically determined by biodegradability of plasticizers.

4.  Cellulose-based Plastics

On extensive modification, cellulose can turn into thermoplastic. Cellulose acetate is an example of this, which is expensive and thereby rarely used for packaging.

PETROLEUM-BASED PLASTICS

Petroleum-based plastics are derived from petrochemicals, which are obtained from fossil crude oil, coal or natural gas.

1.       Polyglycolic Acid (PGA)

Polyglycolic acid, which is an aliphatic polyester often finds its application in medical industry such as PGA sutures for its biodegradability. PLA can degrade into its nontoxic monomer, glycolic acid as it is hydrolytically instable.

2.       Polybutylene Succinate (PBS)

This thermoplastic polymer is used in packaging films for food as well as cosmetics. In addition to this, polybutylene succinate (PBS) is also used as a biodegradable mulching film in the agricultural sector.

3.       Polycaprolactone (PCL)

PCL has gained prominence as an implantable biomaterial. Its biodegradable properties are due to hydrolysis of the ester linkages present in PCL.

4.       Poly Vinyl Alcohol (PVA, PVOH)

Because of its water solubility, biodegradable vinyl polymer offers wide range of applications such as paper coating, textiles coating, food packaging, and healthcare products. 

FACTORS AFFECTING BIODEGRADATION:

ENVIRONMENTAL CONCERNS

1. Oxo-biodegradation:  Biodegradable plastics have some drawbacks. There are some allegations that biodegradable plastics contains pieces of metals that might get released, and oxo-biodegradable plastics tends to produce tiny fragments of plastic that require a great deal of time to degrade regardless of the environmental conditions. The response of the Oxo-biodegradable Plastics Association is that OBD plastics do not contain metals but instead contain metal salts, that are in fact necessary as trace-elements for the human consumption.

2. Effect on Food Supply:  For manufacturing biodegradable plastics, total carbon, fossil fuel along with water are consumed in large amounts, leaving a negative impact on human food supply. For instance, the requirement to produce 1 kg of polylactic acid, which is the most common commercially available compostable plastic, around 2.65 kg of corn is required. Approximately 300 million tons of plastic is produced each year across the globe; and consequently, replacing traditional plastic with corn-derived PLA would result in removal of 800 million tons of corn from the world's food supply.

3. Methane Release: There is one more concern involved that another greenhouse gas, methane, is released during the degradation of biodegradable plastics in an anerobic landfill environment. As a solution, methane gas is captured and used as a source of energy. At present, in United States, most biodegradable plastic goes into landfills where the methane biogas is captured for its usage in clean, inexpensive energy.

4. Biodegradation in the Ocean: Usually the biodegradable plastics that are not degraded to full extent are disposed of in the oceans by waste management facilities, assuming that it would eventually get decomposed in short time period. However, the ocean environment is not optimal for biodegradation, which can be attributed to the fact that biodegradation process favors warm environments with an abundance of microorganisms and oxygen.

According to TechSci Research, Global Plastic Pigments Market By Type (Inorganic Pigments & Organic Pigments), By End-Use Industry (Packaging, Building & Construction, Consumer Goods & Automotive), By Region, Competition, Forecast & Opportunities, 2024, the plastic pigments market, globally, is projected to reach $ 15.09 billion by 2024, growing at a CAGR of 7.21% during the forecast period from $ 10.01 billion in 2018. High demand for packaging in emerging countries is leading to increased consumption of plastic pigments. Growing demand for plastics in automotive industry, increasing significance of aesthetics in packaging, rising industrialization in emerging economies and high demand for high-performance pigments are expected to drive global plastic pigments market during forecast period.

GLOBAL CONSUMPTION OF BIODEGRADABLE POLYMERS:

Europe is the largest producer as well as consumer of biodegradable polymers owing to its legislation as plastic bags are banned in countries such as France and Italy.  Additionally, growing awareness regarding adoption of sustainable plastic solutions coupled with increasing government initiatives to minimize greenhouse gas emissions is positively influencing the market growth in the region.

Asia-Pacific is the second largest region for the consumption of biodegradable plastics. Production capacity of emerging economies like China and Thailand has increased significantly in recent years.

Also, North America is considered as the second-largest producer of biodegradable polymers and a net exporter of PLA. This regional growth can be attributed to the development of composting programs along with apt infrastructure.