a look into the environmental problems caused by biodegradable polymers

1. ARE BIODEGRADABLE POLYMERS TOTALLY
SAFE FOR OUR ENVIRONMENT?
By AKSHAY SREYAS
Polymers play an important role in our daily life. Compared to other polymers,plastic does not
degrade and makes many problem to our earth and environment. Plastics cannot be degraded by
micro organisms. Biodegradable polymers were launched as a remedy for the environmental
problems caused by plastics. It can be decomposed easily by micro organisms .But there is a
question that whether biodegradable polymers are totally safe for our environment. Many studies
now say that biodegradable polymers are not 100% safe. We can look into this matter by discussing
about polymers,plastics,pollution and about biodegradable polymers.
*Polymers
*Plastics and allied problems
*Biodegradable polymers
*Synthesis of biodegradable polymers
*Mechanism of biodegradation
*Advantages of biodegradable polymers
*Are biodegradable polymers totally safe to our environment?
*Conclusion
Polymers
A polymer is macromolecule composed of many repeated subunits known as monomers. Polymers
range from familiar synthetic polymers to natural biopolymers such as DNA and proteins that are
fundamental to biological structure and function.
Plastics and Allied Problems
Plastic, a synthetic polymer consists of a wide range of synthetic or non synthetic organic
compounds that are malleable and so can be moulded into solid objects. Many plastics like poly
erythrene, polypropene,PVC,etc. are thermoplastics which can be moulded again while thermosets
or thermosetting plastics can be moulded only once. Plastics,the main polymers we use in our daily
life,affect our environment very much. Plastic pollution involves the accumulation of plastic
products in the environment that adversely affects our human,habitats and wildlife. Plastic debris is
classified into micro debris and macro debris according to their size. Decomposition of plastics is a
very long process. A foam plastic cup will take 50 years,a plastic beverage holder will take 400
years,a disposable diaper will take 450 years and fishing line will take 600 years to decompose in .
There are some plastics which do not decompose after thousands of years also. Plastic pollution
affects land,ocean and the entire biomass. The widened usage of polymers in the society caused
many problems to our environment. Efforts to reduce the plastic pollution and to promote plastic
recycling have been launched. Today,reusable and biodegradable materials are being used in place
of plastics.
Biodegradable polymers
Biodegradable polymer is a big solution to the environmental pollution caused by synthetic
polymers,mainly plastics. They break down after purpose when disposed emitting natural
byproducts such as gases,water,biomass and inorganic salts. Biodegradable polymers are
synthesized by condensation reactions and ring opening polymerisation reactions. Biodegradable
polymers consists of esters,amide or ether bonds. All biodegradable polymers have numerous
applications and should be stable and durable enough for use but easily degradable. Polylactic acid

2. (PLA),polyglycolic acid (PGA),polyhydroxy butyrate (PHB) etc.are examples of biodegradable
polymers. As degradation needs more end groups and more surface area,they have large surface
area for allowing easy access for either the chemical,light ,or organism and have large end groups.
Biodegradable polymers are hydrophilic and easily get in contact with water soluble enzyme. As
bio degradation is a short process,products of degradation should not be toxic. They should have
good mechanical integrity still degraded.
Synthesis of biodegradable polymers
Biodegradable polymers can be prepared from biobased diols and caroxylic acids such as 1,4-
butanediol,succinic acid and carbohydrates. Important groups of biodegradable polymers are
polyesters,polyurethanes and polyanhydrides. Polyesters are synthesized by condensation of
alcohols and acids, and by ring opening polymerizations etc. The ring opening polymerization of
cyclic dimeric glycolic or lactic acid forms alpha-hydroxy acids which polymerise to form
polyesters. Organometallic initiators like tin,aluminium complexes are used for this polymerisation.
Enzymatic catalysis in polyester formation is also being explored.
image source:wikipedia
Polyanhydrides are synthesized from other polymers using various methods. Polyurethanes are
typically synthesized using a disocyanate,a diol and a polymer chain extender. The use of vegetable
oil and biomass in the formation of urethane is also an active area of research.
Mechanism of biodegradation
Polymers are composed of millions of monomers. Biodegradable polymers decompose to form
gases,salts and biomasses. Complete biodegradation means no monomers are left behind after
biodegradation. There are two mechanisms for biodegradation-one is through physical
decomposition of polymers through reactions such as hydrolysis and photodegradation. The second
mechanism is through aerobic and anaerobic processes. In aerobic process,carbon dioxide and water
are the byproducts. But in anaerobic process,without oxygen,methane is also formed as byproduct
along with carbon dioxide and water. There are many micro organisms that breakdown the
biodegradable polymers. There are several enzymes which accelerate this process. Some of the
examples are proteases,estereases etc.
Advantages of biodegradable polymers
The main advantage of biodegradable polymers over synthetic non biodegradable polymers is the
decrease in environmental pollution. The polymers which do not decompose and even make islands

3. of plastics in oceans make many other problems both to the habitat and living beings of earth. Other
than these, biodegradable polymers have many other important uses in biomedical field,since
biodegradable polymers are made up of non toxic substances. They are used as carriers in medical
field and widely used in nanomedicine .They are also used in tissue engineering and regeneration. A
biodegradable scaffold is obviously preferred as it reduces the risk of immunological reaction and
rejection of the foreign object. Thus biodegradable polymers have greater advantage over non
biodegradable polymers .Catgut is an example of biodegradable polymers.
Are biodegradable polymers totally safe to our environment?
Biodegradable polymers came as a solution to many problems like environmental problems and
problems in medical field that caused by the usage of conventional plastics .But a question arised
recently -are biodegradable polymers totally safe to our environment. Recent studies says that they
are not totally safe to environment. Although they avoid pollution due to the accumulation of
microdebris and macrodebris due to the over usage of conventional plastics,biodegradable polymers
also contribute a little bit of harm to our environment
.
There are allegations that biodegradable plastic bags may release metals
and may require a great deal of time to degrade in certain circumstances and that oligomers of
biodegradable plastic may produce tiny fragments of plastics that do not continue to degrade at any
appreciable rate regardless of the environment. A recent Swedish study found that polyethylene
containing manganese additive stops breaking down when put in compost,probably due to the
influence of ammonia or other gases generated by micro organisms in the compost.
Research from North Carolina University shows that so-called biodegradable
polymers are likely doing more harm than good in landfills because they are releasing powerful
greenhouse gases as they breakdown. In anaerobic decomposition of biodegradable
polymers,methane is a byproduct,which is a greenhouse gas. Methane is produced in anaerobic
decomposition while carbon dioxide is produced in both aerobic and anaerobic decomposition of
biodegradable polymers which is also a greenhouse gas. When we compost these biodegradable
polymers,mainly biodegradable plastics after use,there is no sufficient oxygen under the soil to
promote aerobic decomposition which leads to the production of methane.
Recent studies also says that there is the presence of metals like cobalt,aluminium in the
biodegradable plastic bags produced by some brands. So the cent per cent avoiding of toxicity
cannot be expected by biodegradable polymers. But this problem is not reported in medical field.
The biodegradable plastic bottles and carry bags do not degrade in ocean. A lot of
plastic products labelled biodegradable does not degrade in standard temperature. It will only
decompose in 50 degree celsius and above which is not in ocean .Thus these plastics will pollute
ocean water affecting marine organisms and reefs. Most of the biodegradable polymers are
produced from petroleum. Also the most of biodegradable plastics cannot be recycled .In normal
temperature and conditions,slow decomposition is only possible. In fact,biodegradable plastics
decreases the time of degradation than that of normal plastics. Cobalt and manganese which are
toxic is present in carry bags made of biodegradable polymers.
Thus,biodegradable polymers are not totally safe to our
environment.
Conclusion
Biodegradable polymers is not a complete mean to get rid of environmental hazards due to
conventional plastics. But they are far better than normal plastics. Biodegradable plastics is with the

4. ideology 'go green'.Undoubtedly,biodegradable polymers are a big solution to the problems caused
by normal plastics. Many advanced versions of biodegradable plastics like bioplastics and
compostable plastics are launched. Compostable plastics contain only non toxic substances.
Bioplastics are produced from natural sources,not from petroleum. Thus we can conclude that
biodegradable polymers are good for environment-but not totally. Advancement in technology
related to biodegradable polymers should be achieved-more than bioplastics and compostable
plastics. Then only the term 'biodegradable polymers' become cent per cent truthful.
PREPARED BY AKSHAY SREYAS