Bioplastics report

Plastic products are ubiquitous in our modern society and are associated with convenience
due to their cheap production costs and disposable nature. However, due to its chemically resistant
nature, plastic products have accumulated in the environment post-usage, resisting degradation by
chemical, physical, and biological methods that most other human-generated waste will ultimately
succumb to. Humanity has generated over 8.3 billion metric tons of plastic already, and in 2015
alone 400 million metric tons of plastic was generated.
Of this, 76% has become waste, which totals
6.3 billion metric tons. Some of the waste plastics have accumulated in the ocean have formed a
garbage patch composed of 1.8 trillion bits of plastic waste with an area twice the size of Texas.
Efforts at reusing, reducing, and recycling plastic products have been a good starting point, but the
recycling have its limits as only 10% of plastic products were recycled in 2014 in the US.
consumer products such as plastic bottles have a recycling rate reaching close to 32%, but plastic is
present in so many shapes and forms in our modern life that a majority of products cannot be
processed by recycling plants.
Compounding its harmful effects on the environment is the fact that
99% of the current feedstock for plastics are made from non-renewable fossil fuel based sources,
and the industry is already at $560 Billion USD in 2017 and growing steadily at a rate of 5.3%
CAGR. As such, a novel approach is required to mitigate this ongoing and worsening environmental
From a chemistry perspective, plastics can be defined as organic, polymeric, and malleable
materials designed to be chemically resistant and long-lasting. The monomer feedstock is
polymerized by either free-radical or condensation reactions to form polymer resins. The resins are
then modified by the addition of plasticizers, stabilizers, colorants, and other additives. Finally, the
resin is heated and molded into the desired shape and function of the final product. From a green
chemistry perspective, plastic production go against principles 7 and 10, which are to use renewable
feedstocks as much as possible and to design the product to degrade into innocuous, non-persistent
degradation products. Optimizing the chemistry of plastic to make it biodegradable and renewable is
a rapidly growing field that aims to solve some of the environmental concerns with plastics usage.
A short-term approach that can solve the problem of degradability is the use of
biodegradable additives. There are many companies that manufacture and market this product, such
as BioSphere, Bio-Tec Environmental, EPI, amongst many others.
These companies keep the
formulation of their products as trade secrets, but commonly biodegradable additives contain a
transition metal or enzymatic catalyst, a stabilizer to inactivate the catalyst until after the plastic is
discarded by the consumer, some kind of bulking agent such as starch, and bacterial growth
promoters and nutrients.
These additives break down plastic products post-use by fragmenting
physically through the expansion and weakening of the bulking material, and fragmenting chemically
through catalyzed oxidation or hydrolysis reactions of the polymer chain. The fragments can then
attract bacterial growth easier, aided by other additives in the product. The bacteria can then
decompose the plastic material through its own metabolic pathways, ideally ending up with just
detritus and CO
Biodegradable additives seem promising and is attractive to industry due to its easy
implementation. No modification to feedstock or process is required to implement this change, and
all that is needed is the addition of an extra additive before the molding step. The producers of
biodegradable additives claim that the final plastic product also has the same properties as
unmodified plastic, but this claim is disputed by others. Biodegradable additives can also be used
with most types of plastics, allowing for wide applicability to a large variety of consumer products.
Overall, if the data put forth by the producers of these additives are true, then these additives could
greatly reduce the environmental impact of plastics by shortening the degradation time from
hundreds of years to less than a decade.
Many interest groups have challenged the claims put forth by biodegradable additive
companies. The most contentious issue is whether the plastic product is just fragmenting or if
degradation is actually happening afterwards. Attempts at replicating the results have failed, which
then led to claims of false advertising.
The State of California even fined Walmart $1 million USD for
selling products that claimed to be biodegradable under laws targeting specifically plastic bag
The companies explained the failed replication studies as the result of the researchers not
following the proper degradation conditions, which then raises more concerns about whether those
conditions are actually applicable in real world situations such as in landfills. If those conditions
cannot be met, then the additive cannot do its job. Another concern relates to the degradation by-
products. CO
and methane gas can be generated during the process, which are greenhouse gases
that pose an environmental concern. As well, degradation of polymers can result in generation of
more toxic by-products than the initial plastic, posing a risk to public health and to the environment if
the leachate escapes confinement.
As well, the transition metal salts in the additive itself could
pose an environmental risk.
Lastly, this solution does not solve the problem of non-renewable
feedstock, as fossil fuel is still used to make biodegradable plastics. Despite its downsides and some
government backlash, other governments have actually supported this solution. Saudi Arabia and
the United Arab Emirates have mandated that all plastic bags need to contain a biodegradable
additive, which provided a huge boost to a struggling industry.
The science on biodegradable
additives is not concrete by any means and is shaped equally by economic and political factors as it
is by scientific ones. However, biodegradable additives could be the band-aid on this major problem
of plastic waste accumulation until a longer-term solution is fully developed, such as improving
bioplastics to reach or exceed the properties of current fossil fuel-based plastics.
The best bet for a long-term and sustainable solution, at the moment, seems to be the use of
biobased polymers, more commonly known as bioplastics. The word “biobased” does not
automatically imply biodegradability, but only refers to the fact that these polymers are derived from
biomass, such as plant material and microbiota. In fact, the majority of bioplastics are not
biodegradable due to the fact that they either simply replicate the structure of existing bioplastics in
the case of biobased polyethylene (PE), which is derived from bioethanol
, or are only partially
biobased in the case of the new Dasani water bottle, which only contains 30% biomass
Clearly, not all bioplastics are part of the solution. So, let’s identify three characteristics that
an ideal bioplastic would have. These would be renewability, energy efficiency, and environmentally-
friendliness in terms of biodegradability and greenhouse-gas emissions. The big advantage the
bioplastics have over conventional plastics is, by definition, that they are derived from biomass,
which is a renewable source so the first criteria is easily fulfilled. The second criteria of energy
efficiency is also rather easily fulfilled because bioplastics contain reactive groups containing
oxygen, which can be easily targeted by enzymes, thus lowering the temperature and pressure
necessary for the polymerization reaction to occur
. Let's look at a specific example to further
explore this criterion.
The front-runner that fits this criteria at the moment is polylactic acid (PLA), the most
common form of which is under the trade name “Ingeo” by Greenworks. The PLA monomer is lactic
acid, which is produced by milling corn starch to produce dextrose, and then using microbes to
ferment the dextrose into lactic acid
. The lactic acid molecules undergo a dehydration reaction to
produce lactic acid oligomers, which are then converted to lactide via a process known as thermal
cracking. The final step is the ring opening polymerization (ROP) of lactide into PLA (Figure 1)
There are several areas in this process that can be optimized using green chemistry principles such
as the reusing of solvents and biocatalysts, and the use of more efficient biocatalysts (19). The most
resource-intensive and inefficient step in the process is the production of lactide via thermal cracking
and is an area where green chemistry principles can be applied to make it more cost-effective
(Figure 2). One of the reasons for the inefficiency is the production of water molecules after the
addition of each lactic acid molecule, which makes the reaction increasingly unfavourable. This can
be mitigated by the use of a class of enzymes known as zeolite, which allow for the production of
lactide to be performed in one, efficient step, that produces almost not waste. Zeolites are highly
selective for lactic acid dimers which results in record yields and avoids the problem of racemization
and side-product formation
. Another method by which waste can be reduced is by immobilizing the
biocatalysts on rice husks, in order to reuse them
. This has been done with zeolites, which allows
them to be reused at least 6 consecutive times
. NatureWorks has conducted studies evaluating the
effeciency of its production process and found that Ingeo production utilized 65% than the production
of conventional plastics
. It is unknown whether Ingeo is produced using zeolites but it is a safe
assumption considering the degree of benefit in energy efficiency.
Now, let's evaluate how environmentally friendly PLA is both in terms of biodegradability and
greenhouse gas emissions. First, PLA is one of the few 100% biodegradable bioplastics, along with
polyhydroxyalkanoate (PHA), which is also a widely used commercialized bioplastic. The conditions
required for biodegredation are similar to those required for composting; heat, microbes, and
moisture and they disintegrate into water, CO
, and biomass
. And since PLA is BPA free and
doesn't break down into any toxic compounds, it is much safer for our health. However, to reap the
advantages of biodegradability, the challenge of raising awareness about bioplastic composting
instead of recycling, must be overcome.
But what about emissions? Surely, the CO
produced upon the biodegredation of PLA will
inevitably return to the atmosphere and contribute to climate change? Though this is true, the fact
that the corn or sugar cane from which the bioplastics were derived fix CO
over their lifetime, they
offset the amount that is released at the (Figure 3)
. This result was also confirmed in the same
study conducted by NatureWorks, which found that upon degradation, Ingeo produces 68% fewer
emissions than conventional plastics
. However, it is inevitable that some percentage of the
biodegradable plastic will end up in landfills and contribute to greenhouse gasses, right? Well,
according another peer-reviewed study by NatureWorks, in partnership with Organic Waste Systems
(OWS), this was not the case. Under conditions simulating 100 years in a biologically-active landfill,
the study found no statistically significant difference in biogas production between regular landfills
and those containing PLA
. This is a significant point that eases some of the concerns associated
with a lack of awareness of composting bioplastics.
Finally, there are inevitably drawbacks to bioplastics, namely, insufficient functionality, higher
cost, resource competition, and microplastics due to composites. Although PLA has similar tensile
strength as Acrylonitrile butadiene styrene (ABS), it is not as flexible and becomes unstable at its
glass transition temperature of 60
C compared to 105
C for ABS
. It is also 20-50% more expensive
than conventional oil-based plastics due to the high costs associated with growing and harvesting
the corn and conducting further processing
. The last problem is that, as mentioned earlier, most
bioplastics are either non-biodegradable or not entirely biodegradable (to maintain function), the
latter of which produce microplastics upon degradation, which are extremely harmful to the
Despite these downsides, bioplastics, at this moment, represent the best solution to our
massive problem with plastic pollution, and should be further investigated. The market for bioplastics
seems to agree, as it is expected to grow at a CAGR of 19.2% between 2017 and 2025
, while that
of conventional plastics is expected to be 7% during that same period
. Thus, bioplastics are
headed in the right direction and are a promising solution to our plastic problem.
Figure 1. Chemical formation of PLA
Figure 2. The use of zeolites to improve the production of PLA
Figure 3. The flow of carbon dioxide in the production of bioplastics
Works Cited

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