Is a plastic bag biodegradable?

In this brief discussion we have answered the question “ is a plastic bag biodegradable?”. We have highlighted the biodegradability issues, potential impact of plastic on our environment and recycling of plastic. We have further discussed the role of naturally available material for making plastic and how it is providing an eco-friendly alternative to the conventional plastic bags.

Is a plastic bag biodegradable?

The conventional plastic bags that are made of polyethylene are not biodegradable. It may take upto 450 years for these plastic bags to degrade completely. However, plastic bags that are made from different concentrations of ethylene, biodegrades at different times. 

High Density polyethylene bags that are tough and durable are used for carrying heavy loads and take more than 500 years to complete the biodegradation process. On the contrary, low density polyethylene bags are thin plastic bags that can biodegrade in 2 to 20 years. 

However, as per the definition, biodegradation is the ability of any material that can undergo degradation to simple elements such as carbon dioxide and water by the naturally occurring microbes within a short period of time, that is in weeks or months.

Materials with long degradation time cannot be deemed as biodegradable. Hence, the conventional plastic bag is not biodegradable as it stays in our land for a long period of time causing severe effects to living beings.The table below  gives an idea on the biodegradation rate of plastic bags depending on the composition and arrangement of the monomers.

Types of plasticTime taken for biodegradation
High Density Polyethylene (HDPE)450 years
Low Density polyethylene (LDPE)2 to 20 years
Polypropylene (PP)20 to 30 years
Polylactic acid or bioplastic80 years
Biodegradable plastics3 to 6 months

As can be seen, the high density polyethylene bags that are used for carrying heavy loads such as cements or for making tough corrosion resistant pipes takes longer time for biodegradation. It will be surprising to know that these HDPEs are used for making the water bottles as well. Imagine the tons of plastic waste that this material can generate based on its usage in our everyday life.

Biodegradation time of 20 to 30 years for other types of plastics is also a cause of concern since the production of plastic within these years is many times higher than its degradation. Moreover, the name bioplastic is misleading many buyers as the polylactic acid plastic does not degrade easily under natural conditions and needs an initial composting before biodegradation. 

The initial composting needs to be carried out in an industrial set up that can maintain high temperature for its composting which is not always available. 

With the growing innovation and research for a biocompatible and biodegradable plastic, many options are now available in the market. The biodegradable plastics are worth its name as these can degrade within a few months.

What are the environmental damages caused by plastic bags?

The use of plastic bags has several limitations causing detrimental effects to all living beings in the world. Plastic has become a necessity for packaging and for household purposes. Its use is unavoidable and unless we have an alternate equivalent source, we are stuck with plastic. 

Most of the drawbacks of plastic use is mainly associated with the inability of microbes or the environmental conditions to naturally biodegrade plastics. Let’s summarize some of the detrimental effects from the use of plastic.

  • Release of toxic substances from trashed plastic bags in open areas.
  • Plastic bags dumped in landfills emit dangerous methane and carbon dioxide gasses.
  • Burning of plastic releases toxic chemicals into the air causing air pollution.
  • Numerous diseases are associated with toxins emitted from plastic burning and leachates from landfills.  
  • Littered plastic bags along with fruits and vegetables are eaten by animals causing health problems and even death.
  • Water animals get tangled and drown in plastic bags. Some may cause laceration and choking to sea animals.
  • Plastic fragments or microplastics that are well below the detection level are found in marine habitat. 

What are the recyclability issues with plastic bags?

Plastic bags are recyclable which is done by many recycling centers. Many collection centers are available that accept plastic bag waste such as shopping bags, bread bags, produce bags, and dry cleaning bags. Care should be taken that these bags do not contain sharp things such as staples and each bag that is sent to the recycling center should be clean of food items.

However, with each recycling the quality of plastic is reduced and it finally turns to plastic waste. This downcycling is the reason why many plastic bags can be recycled only a limited number of times. Some of these plastic bags, after recycling, are used to make items such as decks, park benches, picnic tables, and fences.

What are the alternatives for a plastic bag?

There are several alternatives to the use of plastic bags. Bags made of clothes have a superior benefit than most plastic bags. They can be used any number of times and can carry heavy loads. Since these are made from biodegradable materials, clothes are easily biodegraded.

Jute bags also serve a similar purpose and are the most eco friendly material. They are the right replacement for the single use plastic bags as these can be degraded within a year or two and are even compostable.

Going back to the naturally available sources is the best alternative for any synthetic material. Not only are these sources renewable but also their benefits to our environment are many.

Types of plastic bags that are biodegradable

Plastic bags made from polyhydroxyalkanoates (PHAs) are biodegradable as these are natural polyesters made from microorganisms. These plastic bag’s properties are enhanced by chemical modification of the PHAs which render it for multiple applications.

Plastic made from cellulose and its derivatives are also biodegradable plastics as these are made from soft wood which can be composted as well. With extensive modification these cellulose based plastics can show properties of thermoplastic.

Plastic made from lignin biomass and castor oil can be tailor-made and modified to make thermoplastic with high impact resistance and heat resistance. Since they are made from the cheap and naturally degradable biomass, these plastics are eco-friendly.

Research in the field of biodegradable plastic is trying to enhance the properties of the currently available bioplastics to make it more durable and sustainable. 

Conclusion

In this short report we have discussed the biodegradability issues of plastic bags and identified the time taken for biodegradation of different types of plastics. We have also highlighted the key issues with the use of plastic and how it is affecting the living beings on the earth.

On a final note, we have discussed the alternative sources for plastic bags and the biodegradable options available in the market.

Frequently asked questions (FAQs). Is a plastic bag biodegradable?

Is plastic biodegradable?

Plastics that are made from the ethylene monomer are not biodegradable as these are resistant to the activities of most of the naturally occurring microbes. Plastics made from different concentrations of ethylene show a different timeline for biodegradation. 

Bioplastics made from polylactic acid take years for its complete biodegradation. However, if these plastics are composted at high temperature in an industrial set up, they can degrade within a few months. Thus the biodegradability aspect depends on the nature and density of the monomer used.

Why are plastic bags not biodegradable?

Plastic bags are not degraded by naturally occurring microorganisms in any naturally occuring conditions. It will take almost 400 years for it to completely break down. Hence most of the polyethylene based plastics are synthetic polymers that are difficult to break down.

How do you know if plastic is biodegradable?

A plastic can be considered as biodegradable if it breaks down to water, carbon dioxide, and biomass within a given time by the action of naturally occurring microbes. Biodegradable plastics are made from naturally available raw materials such as trees and lignin that are known to decompose by soil bacteria under natural conditions.

What types of plastics are biodegradable?

Plastics that are made from naturally occurring material such as from plants, trees or that produced by microbes are deemed as biodegradable. This is because these materials can biodegrade easily by the action enzymes produced by the microbes in our environment. 

In addition, the availability of oxygen, sunlight and water is necessary for the biodegradation of any materials. This is the reason why most of the materials in landfill take much longer to degrade than on land.

Which is the best biodegradable plastic?

The best biodegradable plastics are the ones that are made from plant based material such as lignin and cellulose. These are not only biodegradable but are also most eco friendly in many ways. These materials can also be modified with other chemicals that further enhances its properties such as durability, strength, and resistance to impact and heat.

Is a plastic bag recyclable?

Plastic bags can be recycled and there are many recycling centers that take almost all kinds of plastic. In order to reduce plastic waste, many Government agencies are setting collection centers where the workers will collect the plastic waste from each and every house on a regular basis. 

The only downside of recycling plastic is that its quality decreases with each recycling and with multiple recycling the plastic turns to a waste.

References

E Carpenter, K Smith, ‘Plastics on the Sargasso Sea surface’, 1972, Science 175: 1240–1241

A Md-Jalil, N Md-Mian, M Rahman, ‘Using Plastic Bags and Its Damaging Impact on Environment and Agriculture: An Alternative Proposal’, 2013, International Journal of Learning & Development. 3: 1–14.

Li, Z., Yang, J. & Loh, X. Polyhydroxyalkanoates: opening doors for a sustainable future. NPG Asia Mater 8, e265 (2016). https://doi.org/10.1038/am.2016.48

What was missing from this post which could have made it better?

Leave a Comment