The that can be degraded when exposed

       The need for biodegradable plastic arose
when several shortcomings of non-degradable plastic became evident. Non-degradable
plastics are carbon based polymers, which are composed of crude oil, cellulose,
coal, natural gas and salt. These are all non-renewable resources, which are
all available in limited supplies and are becoming increasingly expensive. An
approximate of eight percent of world oil production is consumed as feedstock
for plastic manufacturing and as energy in the manufacturing process (Johnston,
2017). Moreover, plastic materials such as bags that are used for an average of
twelve minutes by consumers, take about 500-1000 years to decompose. Hence
several amounts of plastic material are accumulated in landfills or are
polluting the environment. In addition, when plastics encompassing organoch-
lor-based substances such as Poly Vinyl Chloride (PVC) are burnt, toxic amounts
of dioxins, which are highly hazardous compounds are released into the
environment (DiGregorio, 2009). Hence, biodegradable plastic was invented as an
effective alternate to plastic. However, it can be debated whether this
biodegradable plastic is really a better alternative than traditional plastic.
Considering the advantages and disadvantages of biodegradable plastic, it is
not much effective than plastic and it creates more challenges in terms of environment
and waste management.

plastics are plastics that can be degraded when exposed to bacteria and will
generate natural end products such as water and carbon dioxide within a
practical period of time. This time taken to decompose varies depending on the
types of bioplastic material, site of decomposition and environmental
circumstances such as moisture and temperature. Biodegradable plastics can be
further classified into two types: Oxo-biodegradable plastic and
Hydro-biodegradable plastic (Fridovich-Keil, 2016).
Oxo-biodegradable plastic is manufactured by a process called Oxo-degradation. They
are usually made from the by-product of oil refining. They are made
biodegradable by adding a small quantity of pro-degradant additive into the
manufacturing procedure. The pro-degradant additive added changes the
properties or conduct of plastic and turns it biodegradable. After a programmed
time period, the additive reduces the molecular structure of the plastic to a
level that allows bacteria to attain the carbon and hydrogen in the plastic.
Then the material is degraded to carbon dioxide, water and humus (Kinhal,

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     Hydro-biodegradable plastic’s degradation is
induced by hydrolysis. Hydrolysis refers to a chemical reaction in which bonds
of certain substance are broken down with the use of water. The substances that
are broken down are generally in the form of polymers, which are macromolecules
constituted of recurring subunits called monomers. Several plastics under this
classification are composed of large quantities of starch and hence they are
made from renewable sources. However, all the plastics under this category are
not bio based. Some do contain about fifty percentage of synthetic plastic
(which is made from oil.) Certain exceptions such as aliphatic polyesters also are
completely based on crude oil intermediates. Moreover, genetically modified
crops such as genetically modified corn is also used to manufacture certain
plastics under this category. An example of a plastic under this category is polylactic acid (PLA) (C3H4O2)
n  (Antoniou,

    Polylactic acid is a polymer that is mainly
composed of corn starch, cassava roots, or sugarcane. They are primarily made
through two different processes: polymerization and condensation. The most
predominant polymerization technique that is used to manufacture these polymers
is called ring-opening polymerization. This is a form of chain growth polymerization, which is a method in which
unsaturated monomer molecules are added onto a growing polymer chain one at a
time. The ring-opening polymerization process uses metal catalysts along with
lactide monomers (OCHCO2) (which is the lactone derived from lactic acid) to
manufacture larger and longer chains of polylactic acid. The condensation process
is also quite similar with the exception of a few differences. The process is
carried out at less than 200 degrees Celsius. Instead of lactide monomers, this
process utilizes lactic acid monomers CH3CH(OH)COOH. Lactic acid is
made by fermenting corn or other sources of carbohydrates. The other primary
difference between the two processes are the by-products released at the end of

the reaction (Rogers, 2017).

Figure 1:
Structure of lactide (Hild, 2015)      Figure 2: Structure of lactic acid
(Burrell, 2015)

Figure 3: Structure of polylactic acid (Masuelli, 2013)


Polylactic acid
is a thermoplastic material, which is composed of polymers connected by intermolecular
interactions or Van der Waals forces (which are distance-dependent interactions
between molecules). These polymers thence form linear or branched structures.
The more the polymers in a thermoplastic material are cross linked, the effort
put to separate the polymers will also be greater. This resistance is primarily
caused because of the friction produced between the polymers due to the
intermolecular forces holding them together (Kristoff, 2017).

are several solutions that biodegradable plastics such as polylactic acid offer
to problems and shortcomings that arose because of non-biodegradable plastic. Firstly, non-degradable plastics are
mostly derived from crude oil and natural gas, which are all non-renewable
sources. Eventually, these non-renewable will be completely depleted. Whereas,
biodegradable plastic such as polylactic acid is derived from corn, which is a
renewable source (Ramon, 2017). Secondly, as mentioned before traditional
plastics take about 500-1000 years to break down into natural elements. On the
contrary, polylactic acid plastics are compostable, which means that they have
the ability to disintegrate into natural elements such as water and carbon
dioxide in a commercial compost facility. Thirdly, when traditional plastic is
incinerated, especially ones that contain organoch- lor- a, hazardous quantities of dioxins are
emitted into the environment. While, polylactic acid plastic do not produce
toxic dioxins when they are incinerated (West, 2017).

     However, biodegradable plastics also do
have several shortcomings and implications. Firstly, biodegradable plastics at
all times do not immediately decompose. Some of them demand moderately high
temperatures and other controlled conditions to decompose. Secondly, polylactic
acid plastics can only decompose in compost facilities, if they are dumped in
landfills they will not decompose (Jagyasi, 2012). Moreover, the number of
composting facilities are extremely limited globally. Thirdly, when polylactic
plastics are mixed with recyclable plastics, they contaminate the recycling
process and it becomes impossible to recycle as they are chemically different
from traditional plastic. Furthermore, there is also an increasing fear that
using biodegradable plastic may undermine the efforts that are now taken to
recycle plastics and to eradicate the use of plastics. Thirdly, some biodegradable
plastics such as polylactic acid are made from genetically modified corn. Genetically
modified (GM) corn is considered to be innately damaging to the environment and
the ecosystem by some environmentalists, even though it is not evidently
proved, it could be a threat to the environment (Martinko, 2017). Fourthly, biodegradable
plastics such as polylactic acid that are manufactured from corn demand land to
grow corn. In 2014, biodegradable plastics production used up almost a fourth
of the grain production in the United States. When agricultural land is taken
for growing plastic rather than food, it could lead to a substantial increase
in food prices, which would greatly affect numerous people. When corn is grown
through intensive agriculture to produce more biodegradable plastics, it leads
to soil erosion and deforestation, as intensive agriculture disrupts the ecosystem.
Moreover, the farm machinery used to cultivate corn for polylactic acid will release
greenhouse emissions due to the petroleum that fuels the machinery. Water
pollution may also be caused by the excess water that runoffs from the land
where fertilizers and chemicals are used in excessive quantities. These
indirect effects that occur when biodegradable plastics are made in a large
scale are greater that the results that occur when non-degradable plastics are
made (Woodford, 2017).

     When the advantages and disadvantages of
biodegradable plastics are considered and weighed, it is quite evident that
biodegradable plastics create more implications environmentally and
economically rather than solving already existing issues. Biodegradable
plastics are not the solution to safer and cleaner environment, but plastic
management and recycling is. As several environmental campaigners state the
real way to make a difference is one simple step at a time.


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