Bioplastics how they are produced, types, advantages, disadvantages

2697
Egbert Haynes

The bioplastics They are any malleable material based on polymers of petrochemical or biomass origin that are biodegradable. Similar to traditional plastics synthesized from petroleum, these can be molded to produce various objects.

Depending on their origin, bioplastics can be obtained from biomass (biobased) or be of petrochemical origin. On the other hand, depending on their level of decomposition, there are biodegradable and non-biodegradable bioplastics.

Cutlery made of biodegradable starch polyester. Source: Scott Bauer [Public domain]

The rise of bioplastics arises as a response to the inconveniences generated by conventional plastics. These include the accumulation of non-biodegradable plastics in the oceans and landfills..

On the other hand, conventional plastics have a high carbon footprint and a high content of toxic elements. On the other hand, bioplastics have several advantages since they do not produce toxic elements and are generally biodegradable and recyclable..

Among the main disadvantages of bioplastics are their high production cost and lower resistance. In addition, some of the raw materials used are potential foodstuffs, which poses an economic and ethical problem..

Some examples of bioplastic objects are biodegradable bags as well as vehicle parts and mobile phones..

Article index

  • 1 Characteristics of bioplastics
    • 1.1 Economic and environmental importance of bioplastics
    • 1.2 Biodegradability
    • 1.3 Limitations of bioplastics
    • 1.4 Improvement of the properties of bioplastics
  • 2 How are bioplastics produced?
    • 2.1 -Brief history
    • 2.2 -Raw material
    • 2.3 -Production process
    • 2.4 -Manufacture of products based on bioplastics
  • 3 Types
    • 3.1 -Origin
    • 3.2 -level of decomposition
    • 3.3 -Origin and biodegradation
    • 3.4 -Non-biobased-biodegradable
  • 4 Advantages
    • 4.1 They are biodegradable
    • 4.2 They do not pollute the environment
    • 4.3 They have a lower carbon footprint
    • 4.4 Safer to carry food and beverages
  • 5 Disadvantages
    • 5.1 Less resistance
    • 5.2 Higher cost
    • 5.3 Conflict of use
    • 5.4 They are not easy to recycle
  • 6 Examples and their uses of products produced with bioplastics
    • 6.1 -Disposable or disposable objects
    • 6.2 -Objects for durable applications
    • 6.3 -Construction and civil engineering
    • 6.4 -Pharmaceutical applications
    • 6.5 -Medical applications
    • 6.6 -Air, maritime and land transport and industry
    • 6.7 -Agriculture
  • 7 References

Characteristics of bioplastics

Economic and environmental importance of bioplastics

Various utilitarian objects made with bioplastics. Source: Hwaja Götz [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

Recently, there has been a greater scientific and industrial interest in producing plastics from renewable raw materials and that are biodegradable.

This is because the world's oil reserves are being depleted and there is greater awareness of the serious environmental damage caused by petroplastics..

With a growing demand for plastics in the world market, the demand for biodegradable plastics is also increasing.

Biodegradability

Biodegradable bioplastics waste can be treated as organic, fast-degrading and non-polluting waste. For example, they can be used as soil amendments in composting, as they are naturally recycled by biological processes.

Bioplastics with countless commercial uses. Source: F. Kesselring, FKuR Willich [CC BY-SA 3.0 de (https://creativecommons.org/licenses/by-sa/3.0/de/deed.en)], via Wikimedia Commons

Limitations of bioplastics

The manufacture of biodegradable bioplastics faces great challenges, because bioplastics have inferior properties to petroplastics and their application, although growing, is limited.

Improvement of the properties of bioplastics

To improve the properties of bioplastics, mixtures of biopolymers with various types of additives are being developed, such as carbon nanotubes and natural fibers modified by chemical processes..

In general, additives applied to bioplastics improve properties such as:

  • Rigidity and mechanical resistance.
  • Barrier properties against gases and water.
  • Thermoresistance and thermostability.

These properties can be engineered into the bioplastic through chemical preparation and processing methods..

How are bioplastics produced?

Bioplastic for packaging made of thermoplastic starch. Source: Christian Gahle, nova-Institut GmbH [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

-Brief history

Bioplastics predate conventional petroleum-derived synthetic plastics. The use of polymers of plant or animal matter to produce plastic material dates back to the 18th century with the use of natural rubber (latex from Hevea brasiliensis).

The first bioplastic, although it was not given that name, was developed in 1869 by John Wesley Hyatt Jr., who produced a plastic derived from cotton cellulose as a substitute for ivory. Likewise, at the end of the 19th century, casein from milk was used for the production of bioplastics..

In the 1940s, the Ford company explored alternatives for the use of vegetable raw materials to make parts for its cars. This line of research was driven by restrictions on the use of steel by the war.

As a result of this, during the year 1941 the company developed a car model with a body constructed from mainly soy derivatives. However, after the war ended, this initiative was not continued..

By 1947 the first technical bioplastic was produced, Polyamide 11 (Rilsan as a trademark). Later, in the 90s, PLA (polylactic acid), PHA (polyhydroxyalkanoates) and plasticized starches emerged..

-Raw material

Biobased bioplastics are those that are made from plant biomass. The three basic sources of raw material for biobased are the following.

Natural polymers of biomass

You can use natural polymers made directly by plants, such as starch or sugars. For example, "Potato plastic" is a biodegradable bioplastic made from potato starch..

Polymers synthesized from biomass monomers

A second alternative is to synthesize polymers from monomers extracted from plant or animal sources. The difference between this route and the previous one is that an intermediate chemical synthesis is required here..

For example, Bio-PE or green polyethylene is produced from ethanol obtained from sugar cane..

Bioplastics can also be produced from animal sources such as glycosaminoglycans (GAGs), which are eggshell proteins. The advantage of this protein is that it allows to obtain more resistant bioplastics.

Biotechnology based on bacterial cultures

Another way to produce polymers for bioplastics is through biotechnology through bacterial cultures. In this sense, many bacteria synthesize and store polymers that can be extracted and processed..

For this, the bacteria are massively grown in suitable culture media and then processed to purify the specific polymer. For example, PHA (polyhydroxyalkanoates) is synthesized by different bacterial genera growing in a medium with excess carbon and without nitrogen or phosphorus..

The bacteria store the polymer in the form of granules in the cytoplasm, which are extracted by processing the bacterial masses. Another example is PHBV (PolyhydroxyButylValerate), which is obtained from bacteria fed with sugars obtained from plant remains..

The greatest limitation of the bioplastics obtained in this way is the cost of production, mainly due to the culture media required..

Combination of natural polymer and biotechnological polymer

Ohio University developed a fairly strong bioplastic by combining natural rubber with PHBV bioplastic, organic peroxide, and trimethylolpropane triacrylate (TMPTA).

-Production process

Bioplastics are obtained by various processes, depending on the raw material and desired properties. Bioplastics can be obtained through elementary processes or more complex industrial processes.

Basic process

It can be done by cooking and molding in the case of the use of natural polymers, such as starch or corn or potato starch.

Thus, an elementary recipe to produce a bioplastic is to mix cornstarch or potato starch with water, adding glycerin. Subsequently, this mixture is cooked until it thickens, molded and allowed to dry..

Medium complexity processes

In the case of bioplastics produced with polymers synthesized from biomass monomers, the processes are somewhat more complex.

For example, Bio-PE obtained from sugarcane ethanol requires a series of steps. The first thing is to extract the sugar from the cane to obtain ethanol through fermentation and distillation..

Then the ethanol is dehydrated and ethylene is obtained, which must be polymerized. Finally, using thermoforming machines, objects are manufactured based on this bioplastic.

Complex and more expensive processes

When referring to bioplastics produced from polymers obtained by biotechnology, complexity and costs increase. This is because bacterial cultures are involved that require culture media and specific growth conditions..

This process is based on the fact that certain bacteria produce natural polymers that they are able to store inside. Therefore, starting from the appropriate nutritional elements, these microorganisms are cultivated and processed to extract the polymers..

Bioplastics can also be made from some algae such as Botryococcus braunii. This microalgae is capable of producing and even excreting hydrocarbons into the environment, from which fuels or bioplastics are obtained..

-Manufacture of products based on bioplastics

The basic principle is the molding of the object, thanks to the plastic properties of this compound using pressure and heat. The processing is done by extrusion, injection, injection and blowing, preform blowing and thermoforming and finally it is subjected to cooling.

Types

Packaging made of cellulose acetate. Source: Christian Gahle, nova-Institut GmbH [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

The approaches to classifying bioplastics are diverse and not without controversy. In any case, the criteria used to define the different types are the origin and level of decomposition..

-Source

According to a generalized approach, bioplastics can be classified by their origin as biobased or non-biobased. In the first case, the polymers are obtained from plant, animal or bacterial biomass and therefore are renewable resources.

On the other hand, non-biobased bioplastics are those produced with polymers synthesized from petroleum. However, as they come from a non-renewable resource, some specialists consider that they should not be treated as bioplastics.

-Decomposition level

Regarding the level of decomposition, bioplastics can be biodegradable or not. The biodegradable ones decompose in relatively short periods of time (days to a few months) when subjected to suitable conditions.

For their part, non-biodegradable bioplastics behave like conventional plastics of petrochemical origin. In this case, the decomposition period is measured in decades and even centuries..

There is also controversy regarding this criterion, since some scholars consider that a true bioplastic must be biodegradable..

-Origin and biodegradation

When the two previous criteria are combined (origin and level of decomposition), bioplastics can be classified into three groups:

  1. From renewable raw materials (biobased) and biodegradable.
  2. Those obtained from renewable raw materials (biobased), but are not biodegradable.
  3. Obtained from raw materials of petrochemical origin, but which are biodegradable.

It is important to note that to consider a polymer as bioplastic it must enter one of these three combinations.

Biobased-biodegradable

Among the biobased and biodegradable bioplastics we have polylactic acid (PLA) and polyhydroxyalkanoate (PHA). PLA is one of the most used bioplastics and is obtained mainly from corn.

This bioplastic has similar properties to polyethylene terephthalate (PET, conventional polyester type plastic), although it is less resistant to high temperatures.

For its part, PHA has variable properties depending on the specific polymer that constitutes it. It is obtained from plant cells or through biotechnology from bacterial cultures.

These bioplastics are very sensitive to processing conditions and their cost is up to ten times higher than conventional plastics.

Another example of this category is PHBV (PolyhydroxyButylValerate), which is obtained from plant remains..

Biobased-non-biodegradable

In this group we have bio-polyethylene (BIO-PE), with properties similar to those of conventional polyethylene. For its part, Bio-PET has characteristics similar to polyethylene terephthalate.

Both bioplastics are commonly manufactured from sugar cane, obtaining bioethanol as an intermediate product..

Bio-polyamide (PA), which is a recyclable bioplastic with excellent thermal insulation properties, also belongs to this category..

-Non-biobased-biodegradable

Biodegradability has to do with the chemical structure of the polymer and not with the type of raw material used. Therefore, biodegradable plastics can be obtained from petroleum with proper processing..

An example of this type of bioplastics are polycaprolactones (PCL), which are used in the manufacture of polyurethanes. This is a bioplastic obtained from petroleum derivatives like polybutylene succinate (PBS).

Advantage

Candy wrapper made of PLA (polylactic acid). Source: F. Kesselring, FKuR Willich [CC BY-SA 3.0 de (https://creativecommons.org/licenses/by-sa/3.0/de/deed.en)]

They are biodegradable

Although not all bioplastics are biodegradable, the truth is that for many people this is their fundamental characteristic. In fact, the search for that property is one of the fundamental engines of the bioplastics boom.

Conventional petroleum-based, non-biodegradable plastics take hundreds and even thousands of years to break down. This situation represents a serious problem, as landfills and oceans fill with plastics..

For this reason, biodegradability is a very relevant advantage, since these materials can decompose in weeks, months or a few years..

They do not pollute the environment

Because they are biodegradable materials, bioplastics stop occupying space as garbage. In addition, they have the additional advantage that in most cases they do not contain toxic elements that can be released into the environment..

They have a lower carbon footprint

Both in the bioplastics production process, as in their decomposition, less CO2 is released than in the case of conventional plastics. In many cases, they do not release methane or do so in low quantities and therefore have little impact on the greenhouse effect..

For example, bioplastics obtained from sugar cane ethanol reduce CO2 emissions by up to 75% compared to petroleum derivatives.

Safer to carry food and drinks

Generally, toxic substances are not used in the production and composition of bioplastics. Therefore, they represent less risk of contamination for the food or beverages contained in them..

Unlike conventional plastics that can produce dioxins and other polluting components, biobased bioplastics are harmless.

Disadvantages

The drawbacks are mainly related to the type of bioplastic used. Among others we have the following.

Less resistance

One limitation that most bioplastics have compared to conventional plastics is their lower resistance. However, this property is associated with its ability to biodegrade..

Higher cost

In some cases, the raw materials used for the production of bioplastics are more expensive than those from petroleum.

On the other hand, the production of some bioplastics implies higher processing costs. In particular, these production costs are higher in those produced through biotechnological processes, including the mass cultivation of bacteria..

Conflict of use

Bioplastics produced from food raw materials compete with human needs. Therefore, since it is more profitable to dedicate crops to the production of bioplastics, these are withdrawn from the food production circuit.

However, this disadvantage does not apply to those bioplastics obtained from inedible waste. Among these wastes we have crop remains, inedible algae, lignin, egg shells or lobster exoskeletons..

They are not easy to recycle

PLA bioplastic is very similar to conventional PET (polyethylene terephthalate) plastic, but it is not recyclable. Therefore, if both types of plastic are mixed in a recycling container, this content cannot be recycled..

In this regard, there are fears that the increasing use of PLA could hamper existing efforts to recycle plastics..

Examples and their uses of products produced with bioplastics

Wine container made with bioplastic from agricultural waste and mycelia. Source: Mycobond [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)]

-Disposable or disposable objects

The items that generate the most waste are containers, wrappers, plates and cutlery linked to fast food and shopping bags. Therefore, in this field biodegradable bioplastics play a relevant role.

For this reason, various products based on bioplastics have been developed in order to influence the reduction of waste generation. Among others, we have the biodegradable bag made with BASF's Ecovio or the plastic bottle made of PLA obtained from corn by Safiplast in Spain..

Water capsules

The Ooho company devised biodegradable capsules from seaweed with water, instead of the traditional bottles. This proposal has been very innovative and successful and has already been tested in the London marathon.

farming

In some crops such as strawberries, a common practice is to cover the soil with a plastic sheet in order to control weeds and avoid freezing. In this sense, bioplastic padding such as Agrobiofilm have been developed to replace conventional plastics.

-Objects for durable applications

The use of bioplastics is not restricted to objects of use and disposal but can be used in more durable objects. For example, Zoë b Organic's company produces beach toys.

Complex equipment components

Toyota uses bioplastics in some auto parts, such as components for air conditioners and control panels. For this, it uses bioplastics such as Bio-PET and PLA.

For its part, Fujitsu uses bioplastics to make computer mice and keyboard parts. In the case of the Samsung company, some mobile phones have housings made largely of bioplastic.

-Construction and civil engineering

Starch bioplastics have been used as construction materials and bioplastics reinforced with nanofibers in electrical installations.

In addition, they have been used in the elaboration of bioplastic woods for furniture, which are not attacked by xylophagous insects and do not rot with humidity.

-Pharmaceutical applications

They have been made with bioplastic capsules containing drugs and drug vehicles that are slowly released. Thus, the bioavailability of drugs is regulated over time (the dose that the patient receives in a given time).

-Medical applications

Cellulose bioplastics applicable in implants, tissue engineering, chitin and chitosan bioplastics have been manufactured for wound protection, bone tissue engineering and human skin regeneration.

Cellulose bioplastics have also been manufactured for biosensors, mixtures with hydroxyapatite for the manufacture of dental implants, bioplastic fibers in catheters, among others..

-Air, sea and land transport and industry

Rigid foams based on vegetable oils (bioplastics) have been used, both in industrial and transport devices; auto parts and aerospace parts.

Electronic components of cell phones, computers, audio and video devices have also been produced from bioplastics..

-farming

Bioplastic hydrogels, which absorb and retain water and can release it slowly, are useful as protective covers for the cultivated soil, maintaining its humidity and favoring the growth of agricultural plantations in dry regions and in low rainy seasons..

References

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  3. El-Kadi S (2010). Bioplastic production from inexpensive sources. ISBN 9783639263725; VDM Verlag Dr. Müller Publishing, Berlin, Germany. 145 p.
  4. Labeaga-Viteri A (2018). Biodegradable polymers. Importance and potential applications. National University of Distance Education. Faculty of Sciences, Department of Inorganic Chemistry and Chemical Engineering. Master's Degree in Chemical Science and Technology. 50 p.
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