Bioplastic


Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc. Bioplastic can be made from agricultural by-products and also from used plastic bottles and other containers using microorganisms. Common plastics, such as fossil-fuel plastics are derived from petroleum or natural gas. Not all bioplastics are biodegradable nor biodegrade more readily than commodity fossil-fuel derived plastics. Bioplastics are usually derived from sugar derivatives, including starch, cellulose, and lactic acid. As of 2014, bioplastics represented approximately 0.2% of the global polymer market.

Applications

Bioplastics are used for disposable items, such as packaging, crockery, cutlery, pots, bowls, and straws. Few commercial applications exist for bioplastics. In principle they could replace many applications for petroleum-derived plastics, however cost and performance remain problematic. As a matter of fact, their usage is financially favourable only if supported by specific regulations limiting the usage of conventional plastics. Typical is the example of Italy, where biodegradable plastic bags and shoppers are compulsory since 2011 with the introduction of a specific law. Beyond structural materials, electroactive bioplastics are being developed that promise to carry electric current.
Biopolymers are available as coatings for paper rather than the more common petrochemical coatings.

Types

Starch-based plastics

starch currently represents the most widely used bioplastic, constituting about 50 percent of the bioplastics market. Simple starch bioplastic film can be made at home by gelatinizing starch and solution casting. Pure starch is able to absorb humidity, and is thus a suitable material for the production of drug capsules by the pharmaceutical sector. However, pure starch-based bioplastic is brittle. Plasticizer such as glycerol, glycol, and sorbitol and can also be added so that the starch can also be processed thermo-plastically. The characteristics of the resulting bioplastic can be tailored to specific needs by adjusting the amounts of these additives. Conventional polymer processing techniques can be used to process starch into bioplastic, such as extrusion, injection molding, compression molding and solution casting. The properties of starch bioplastic is largely influenced by amylose/amylopectin ratio. Generally, high-amylose starch can result in better mechanical properties. However, high-amylose starch has less processiblity because of its higher gelatinization temperature and higher melt viscosity.
Starch-based bioplastics are often blended with biodegradable polyesters to produce starch/polylactic acid, starch/polycaprolactone or starch/Ecoflex blends. These blends are used for industrial applications and are also compostable. Other producers, such as Roquette, have developed other starch/polyolefin blends. These blends are not biodegradable, but have a lower carbon footprint than petroleum-based plastics used for the same applications.
Due to the origin of its raw material, starch is cheap, abundant, and renewable.
Starch-based plastics are complex blends of starch with biodegradable or compostable plastics such as polylactic acid, polybutylene adipate terephthalate, polybutylene succinate, polycaprolactone, and polyhydroxyalkanoates. These complex blends improve water resistance as well as processing and mechanical properties.
Starch-based films are made mainly from starch blended with thermoplastic polyesters to form biodegradable and compostable products. These films are seen specifically in consumer goods packaging of magazine wrappings and bubble films. In food packaging, these films are seen as bakery or fruit and vegetable bags. Composting bags with this films are used in selective collecting of organic waste. Further, a new starch-based film was developed by Agricultural Research Service scientists can even be used as a paper.
Starch-based nanocomposites have been widely studied, showing improved mechanical properties, thermal stability, moisture resistance, and gas barrier properties.

Cellulose-based plastics

bioplastics are mainly the cellulose esters, and their derivatives, including celluloid.
Cellulose can become thermoplastic when extensively modified. An example of this is cellulose acetate, which is expensive and therefore rarely used for packaging. However, cellulosic fibers added to starches can improve mechanical properties, permeability to gas, and water resistance due to being less hydrophilic than starch.
A group at Shanghai University was able to construct a novel green plastic based on cellulose through a method called hot pressing.

Protein-based plastics

Bioplastics can be made from proteins from different sources. For example, wheat gluten and casein show promising properties as a raw material for different biodegradable polymers.
Additionally, soy protein is being considered as another source of bioplastic. Soy proteins have been used in plastic production for over one hundred years. For example, body panels of an original Ford automobile were made of soy-based plastic.
There are difficulties with using soy protein-based plastics due to their water sensitivity and relatively high cost. Therefore, producing blends of soy protein with some already-available biodegradable polyesters improves the water sensitivity and cost.

Some aliphatic polyesters

The aliphatic biopolyesters are mainly polyhydroxyalkanoates like the poly-3-hydroxybutyrate, polyhydroxyvalerate and polyhydroxyhexanoate.

Polylactic acid (PLA)

is a transparent plastic produced from corn or dextrose. Superficially, it is similar to conventional petrochemical-based mass plastics like PS. It has the distinct advantage of degrading to nontoxic products. Unfortunately it exhibits inferior impact strength, thermal robustness, and barrier properties. PLA and PLA blends generally come in the form of granulates with various properties, and are used in the plastic processing industry for the production of films, fibers, plastic containers, cups and bottles.
PLA is also the most common type of plastic filament used for home fused deposition modeling.

Poly-3-hydroxybutyrate

The biopolymer poly-3-hydroxybutyrate is a polyester produced by certain bacteria processing glucose, corn starch or wastewater. Its characteristics are similar to those of the petroplastic polypropylene. PHB production is increasing. The South American sugar industry, for example, has decided to expand PHB production to an industrial scale. PHB is distinguished primarily by its physical characteristics. It can be processed into a transparent film with a melting point higher than 130 degrees Celsius, and is biodegradable without residue.

Polyhydroxyalkanoates

are linear polyesters produced in nature by bacterial fermentation of sugar or lipids. They are produced by the bacteria to store carbon and energy. In industrial production, the polyester is extracted and purified from the bacteria by optimizing the conditions for the fermentation of sugar. More than 150 different monomers can be combined within this family to give materials with extremely different properties. PHA is more ductile and less elastic than other plastics, and it is also biodegradable. These plastics are being widely used in the medical industry.

Polyamide 11

is a biopolymer derived from natural oil. It is also known under the tradename Rilsan B, commercialized by Arkema. PA 11 belongs to the technical polymers family and is not biodegradable. Its properties are similar to those of PA 12, although emissions of greenhouse gases and consumption of nonrenewable resources are reduced during its production. Its thermal resistance is also superior to that of PA 12. It is used in high-performance applications like automotive fuel lines, pneumatic airbrake tubing, electrical cable antitermite sheathing, flexible oil and gas pipes, control fluid umbilicals, sports shoes, electronic device components, and catheters.
A similar plastic is Polyamide 410, derived 70% from castor oil, under the trade name EcoPaXX, commercialized by DSM.
PA 410 is a high-performance polyamide that combines the benefits of a high melting point, low moisture absorption and excellent resistance to various chemical substances.

Bio-derived polyethylene

The basic building block of polyethylene is ethylene. Ethylene is chemically similar to, and can be derived from ethanol, which can be produced by fermentation of agricultural feedstocks such as sugar cane or corn. Bio-derived polyethylene is chemically and physically identical to traditional polyethylene – it does not biodegrade but can be recycled. The Brazilian chemicals group Braskem claims that using its method of producing polyethylene from sugar cane ethanol captures 2.15 tonnes of per tonne of Green Polyethylene produced.

Genetically modified feedstocks

With GM corn being a common feedstock, it is unsurprising that some bioplastics are made from this.
Under the bioplastics manufacturing technologies there is the "plant factory" model, which uses genetically modified crops or genetically modified bacteria to optimise efficiency.

Polyhydroxyurethanes

Recently, there have been a large emphasis on producing biobased and isocyanate-free polyurethanes. One such example utilizes a spontaneous reaction between polyamines and cyclic carbonates to produce polyhydroxurethanes. Unlike traditional cross-linked polyurethanes, cross-linked polyhydroxyurethanes have been shown to be capable of recycling and reprocessing through dynamic transcarbamoylation reactions.

Lipid derived polymers

A number bioplastic classes have been synthesized from plant and animal derived fats and oils. Polyurethanes, polyesters, epoxy resins and a number of other types of polymers have been developed with comparable properties to crude oil based materials. The recent development of olefin metathesis has opened a wide variety of feedstocks to economical conversion into biomonomers and polymers. With the growing production of traditional vegetable oils as well as low cost microalgae derived oils, there is huge potential for growth in this area.

Environmental impact

Materials such as starch, cellulose, wood, sugar and biomass are used as a substitute for fossil fuel resources to produce bioplastics; this makes the production of bioplastics a more sustainable activity compared to conventional plastic production. The environmental impact of bioplastics is often debated, as there are many different metrics for "greenness". Hence bioplastic environmental impacts are categorized into nonrenewable energy use, climate change, eutrophication and acidification. Bioplastic production significantly reduces greenhouse gas emissions and decreases non-renewable energy consumption. Firms worldwide would also be able to increase the environmental sustainability of their products by using bioplastics
Although bioplastics save more nonrenewable energy than conventional plastics and emit less GHG compared to conventional plastics, bioplastics also have negative environmental impacts such as eutrophication and acidification. Bioplastics induce higher eutrophication potentials than conventional plastics. Biomass production during industrial farming practices causes nitrate and phosphate to filtrate into water bodies; this causes eutrophication, the process in which a body of water richness gains excessive richness of nutrients. Eutrophication is a threat to water resources around the world since it causes harmful algal blooms that create oxygen dead zones, killing aquatic animals. Bioplastics also increase acidification. The high increase in eutrophication and acidification caused by bioplastics is also caused by using chemical fertilizer in the cultivation of renewable raw materials to produce bioplastics.
Other environmental impacts of bioplastics include exerting lower human and terrestrial ecotoxicity and carcinogenic potentials compared to conventional plastics. However, bioplastics exert higher aquatic ecotoxicity than conventional materials. Bioplastics and other bio-based materials increase stratospheric ozone depletion compared to conventional plastics; this is a result of nitrous oxide emissions during fertilizer application during industrial farming for biomass production. Artificial fertilizer increase nitrous oxide emissions especially when the crop does not need all the nitrogen. Minor environmental impacts of bioplastics include toxicity through using pesticides on the crops used to make bioplastics. Bioplastics also cause carbon dioxide emissions from harvesting vehicles. Other minor environmental impacts include high water consumption for biomass cultivation, soil erosion, soil carbon losses and loss of biodiversity, and they are mainly are a result of land use associated with bioplastics. Land use for bioplastics production leads to lost carbon sequestration and increases the carbon costs while diverting land from its existing uses
Although bioplastics are extremely advantageous because they reduce non-renewable consumption and GHG emissions, they also negatively affect the environment through land and water consumption, using pesticide and fertilizer, eutrophication and acidification; hence one's preference for either bioplastics or conventional plastics depends on what one considers the most important environmental impact.
Another issue with bioplastics, is that some bioplastics are made from the edible parts of crops.
This makes the bioplastics compete with food production because the crops that produce bioplastics can also be used to feed people. These bioplastics are called "1st generation feedstock bioplastics".
2nd generation feedstock bioplastics use non-food crops or waste materials from 1st generation feedstock.
3rd generation feedstock bioplastics use algae as the feedstock.

Biodegradation of Bioplastics

Biodegradation of any plastic is a process that happens at solid/liquid interface whereby the enzymes in the liquid phase depolymerize the solid phase Both bioplastics and conventional plastics containing additives are able to biodegrade. Bioplastics are able to biodegrade in different environments hence they are more acceptable than conventional plastics. Biodegradability of bioplastics occurs under various environmental conditions including soil, aquatic environments and compost. Both the structure and composition of biopolymer or bio-composite have an effect on the biodegradation process, hence changing the composition and structure might increase biodegradability. Soil and compost as environment conditions are more efficient in biodegradation due to their high microbial diversity. Composting not only biodegrades bioplastics efficiently but it also significantly reduces the emission of greenhouse gases. Biodegradability of bioplastics in compost environments can be upgraded by adding more soluble sugar and increasing temperature. Soil environments on the other hand have high diversity of microorganisms making it easier for biodegradation of bioplastics to occur. However, bioplastics in soil environments need higher temperatures and a longer time to biodegrade. Some bioplastics biodegrade more efficiently in water bodies and marine systems; however, this causes danger to marine ecosystems and freshwater. Hence it is accurate to conclude that biodegradation of bioplastics in water bodies which leads to the death of aquatic organisms and unhealthy water can be noted as one of the negative environmental impacts of bioplastics.

Industry and markets

While plastics based on organic materials were manufactured by chemical companies throughout the 20th century, the first company solely focused on bioplastics- Marlborough Biopolymers- was founded in 1983. However, Marlborough and other ventures that followed failed to find commercial success, with the first such company to secure long-term financial success being the Italian company Novamont, founded in 1989.
The expense and time requirements of researching and testing new bio-based and biodegradable polymers have placed bioplastics at a commercial disadvantage compared to petrochemical-based plastics. Bioplastics remain less than one percent of all plastics manufactured worldwide, and until very recently have been an average of 2-4 times more expensive to manufacture than petrochemical plastics. Most bioplastics do not yet save more carbon emissions than are required to manufacture them. Finally, the industry faces logistical problems with both material sources and waste disposal infrastructure. As most bioplastics are produced from plant sugars, starches, or oils, it is estimated that replacing 250 million tons of the plastic manufactured each year with bio-based plastics would require 100 million hectares of land, or 7 percent of the arable land on Earth. And when bioplastics reach the end of their life cycle, those designed to be compostable and marketed as biodegradable are often sent to landfills due to the lack of proper composting facilities or waste sorting, where they then release methane as they break down anaerobically.
Despite this, the bioplastics industry has grown by 20-30% a year. BCC Research forecast that the global market for biodegradable polymers would grow at a compound average growth rate of more than 17 percent through 2012, and this rate of growth has actually been exceeded. Bio-based plastics are predicted to make up 5% of all manufactured plastics in 2020, and 40% of all manufactured plastics in 2030. Ceresana predicts that when bioplastics reach 5% of the plastics market in 2020, the market for bio-based plastics will be worth 5.8 billion dollars, three times the size of the bioplastics market in 2014. The largest demand for bioplastics has been in packaging, driven by widespread concern over the use of petrochemical plastics in disposable, one-use products that are then sequestered in landfills or the natural environment. Packaging continues to provide 60% of the market for bioplastic, and to account for the largest share of growth in the industry. There has been a shift in the market for an increased demand of bioplastics, especially for sustainable packaging. This has been seen specifically in Western Europe, which accounted for more than 45% of the global biodegradable plastics demand in 2014. This demand from consumers for more sustainable options was also seen in recent policies; Italy has banned the use of petroleum-based plastic bags, and there is a tax on use of petroleum based plastic bags in Germany
However, the industry in biobased polymers has not grown as rapidly as some have predicted. The NNFCC predicted that the industry would exceed 2.1 million tonnes produced each year by 2013, but by in 2017, only 2.05 million tonnes of bioplastic were produced in that year. This remains only a small fraction of all plastics manufacturing, which produced a total 292 million tonnes of thermoplastics in 2015. As production expands, there remain no universal standards governing bioplastics and their manufacture or disposal. This includes a lack of any regulation on the amount of sustainably sourced material in a product required for it to be marketed as a bioplastic. According to Market and Market, the global biodegradable plastics market is just beginning and only accounts for less than 1% of the overall plastics market made from cellulose acetate biograde
Because of the fragmentation in the market and ambiguous definitions it is difficult to describe the total market size for bioplastics, but estimates put global production capacity at 327,000 tonnes. In contrast, global production of polyethylene and polypropylene, the world's leading petrochemical derived polyolefins, was estimated at over 150 million tonnes in 2015.
COPA and COGEGA have made an assessment of the potential of bioplastics in different sectors of the European economy:

History and development of bioplastics

*not a comprehensive list; inventions pulled by the author to show versatility of bioplastics and important breakthroughs; new applications and inventions of bioplastics happen each year
YearBioplastic Discovery or Development
1862Parkesine - Alexander Parkes
1868Celluloid - John Wesley Hyatt
1897Galalith - German chemists
1907Bakelite - Leo Baekeland
1912Cellophane - Jacques E. Brandenberger
1920sPolylactic ACid - Wallace Carothers
1926Polyhydroxybutyrate - Maurice Lemoigne
1930sSoy bean-based bioplastic car - Henry Ford
1983Biopal - Marlborough Biopolymers
1989PLA from corn - Dr. Patrick R. Gruber; Matter-bi - Novamount
1992PHB can be produced by Arabidopsis thaliana
1998Bioflex film leads to many different applications of bioplastic
2001PHB can be produced by elephant grass
2007Mirel by Metabolic inc. is market tested
2012Bioplastic is developed from seaweed
2013Bioplastic made from blood and a cross-linking agent which is used in medical procedures
2014Bioplastic made from vegetable waste
2016Car bumper made from banana peel bioplastic
2017Bioplastics made from lignocellulosic resources
2018Bioplastic furniture, bio-nylon, packaging from fruit

made with bioplastics

Testing procedures

Industrial compostability – EN 13432, ASTM D6400

The EN 13432 industrial standard must be met in order to claim that a plastic product is compostable in the European marketplace. In summary, it requires multiple tests and sets pass/fail criteria, including disintegration of the finished item within 12 weeks, biodegradation of polymeric ingredients within 180 days, plant toxicity and heavy metals. The ASTM 6400 standard is the regulatory framework for the United States and as similar requirements.
Many starch-based plastics, PLA-based plastics and certain aliphatic-aromatic co-polyester compounds, such as succinates and adipates, have obtained these certificates. Additive-based bioplastics sold as photodegradable or Oxo Biodegradable do not comply with these standards in their current form.

Compostability – ASTM D6002

The ASTM D 6002 method for determining the compostability of a plastic defined the word compostable as follows:
that which is capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds and biomass at a rate consistent with known compostable materials.

This definition drew much criticism because, contrary to the way the word is traditionally defined, it completely divorces the process of "composting" from the necessity of it leading to humus/compost as the end product. The only criterion this standard does describe is that a compostable plastic must look to be going away as fast as something else one has already established to be compostable under the traditional definition.

Withdrawal of ASTM D 6002

In January 2011, the ASTM withdrew standard ASTM D 6002, which had provided plastic manufacturers with the legal credibility to label a plastic as compostable. Its description is as follows:
This guide covered suggested criteria, procedures, and a general approach to establish the compostability of environmentally degradable plastics.

The ASTM has yet to replace this standard.

Biobased – ASTM D6866

The ASTM D6866 method has been developed to certify the biologically derived content of bioplastics. Cosmic rays colliding with the atmosphere mean that some of the carbon is the radioactive isotope carbon-14. CO2 from the atmosphere is used by plants in photosynthesis, so new plant material will contain both carbon-14 and carbon-12. Under the right conditions, and over geological timescales, the remains of living organisms can be transformed into fossil fuels. After ~100,000 years all the carbon-14 present in the original organic material will have undergone radioactive decay leaving only carbon-12. A product made from biomass will have a relatively high level of carbon-14, while a product made from petrochemicals will have no carbon-14. The percentage of renewable carbon in a material can be measured with an accelerator mass spectrometer.
There is an important difference between biodegradability and biobased content. A bioplastic such as high-density polyethylene can be 100% biobased, yet be non-biodegradable. These bioplastics such as HDPE nonetheless play an important role in greenhouse gas abatement, particularly when they are combusted for energy production. The biobased component of these bioplastics is considered carbon-neutral since their origin is from biomass.

Anaerobic biodegradability – ASTM D5511-02 and ASTM D5526

The ASTM D5511-12 and ASTM D5526-12 are testing methods that comply with international standards such as the ISO DIS 15985 for the biodegradability of plastic.