Bioplastic

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Bioplastics are plastics derived from renewable biomass sources, such as vegetable fats and oils, corn starch, pea starch[1] or microbiota.[2] Common plastics, such as fossil-fuel plastics, are derived from petroleum; these plastics rely more on fossil fuels and produce more greenhouse gas. Some, but not all, bioplastics are designed to biodegrade. Biodegradable bioplastics can break down in either anaerobic or aerobic environments, depending on how they are manufactured. There is a variety of materials that bioplastics can be composed of, including: starches, cellulose, or other biopolymers. Some common applications of bioplastics are packaging materials, dining utensils, food packaging, and insulation.[3]

IUPAC definition

Biobased polymer derived from the biomass or issued from monomers derived
from the biomass and which, at some stage in its processing into finished
products, can be shaped by flow.

Note 1: Bioplastic is generally used as the opposite of polymer derived from
fossil resources.

Note 2: Bioplastic is misleading because it suggests that any polymer derived
from the biomass is environmentally friendly.

Note 3: The use of the term “bioplastic” is discouraged. Use the expression
“biobased polymer”.

Note 4: A biobased polymer similar to a petrobased one does not imply any
superiority with respect to the environment unless the comparison of respective
life cycle assessments is favourable.[4]

Biodegradable plastic utensils
Packaging peanuts made from bioplastics (thermoplastic starch)
Plastics packaging made from bioplastics and other biodegradable plastics

Applications[edit]

Flower wrapping made of PLA-blend bio-flex

Biodegradable bioplastics are used for disposable items, such as [packaging] and catering items (crockery, cutlery, pots, bowls, straws). They are also often used for bags, trays, containers for fruit, vegetables, eggs and meat, bottles for soft drinks and dairy products, and blister foils for fruit and vegetables.

Nondisposable applications include mobile phone casings, carpet fibres, and car interiors, fuel line and plastic pipe applications, and new electroactive bioplastics are being developed that can be used to carry electrical current.[5] In these areas, the goal is not biodegradability, but to create items from sustainable resources.

Medical implants made of PLA, which dissolve in the body, save patients a second operation. Compostable mulch films for agriculture, already often produced from starch polymers, do not have to be collected after use and can be left on the fields.[6]

Plastic types[edit]

Starch-based plastics[edit]

Constituting about 50 percent of the bioplastics market,[citation needed] thermoplastic starch, currently represents the most widely used bioplastic. Pure starch possesses the characteristic of being able to absorb humidity, and is thus being used for the production of drug capsules in the pharmaceutical sector. Flexibiliser and plasticiser such as sorbitol and glycerine are added so the starch can also be processed thermo-plastically. By varying the amounts of these additives, the characteristic of the material can be tailored to specific needs (also called "thermo-plastical starch"). Simple starch plastic can be made at home.[7]

Industrially, starch-based bioplastics are often blended with biodegradable polyesters. These blends are mainly starch/polycaprolactone[8] or starch/Ecoflex[9] (polybutylene adipate-co-terephthalate produced by BASF[10]). These blends remain compostables. Other producers, such as Roquette, have developed another strategy based on starch/polyeolefine blends. These blends are no longer biodegradables, but display a lower carbon footprint compared to the corresponding petroleum-based plastics.[11]

Cellulose-based plastics[edit]

Packaging blister made from cellulose acetate, a bioplastic

Cellulose bioplastics are mainly the cellulose esters, (including cellulose acetate and nitrocellulose) and their derivatives, including celluloid.

Some aliphatic polyesters[edit]

The aliphatic biopolyesters are mainly polyhydroxyalkanoates (PHAs) like the poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and polyhydroxyhexanoate (PHH).

Polylactic acid (PLA)[edit]

Mulch film made of polylactic acid (PLA)-blend bio-flex

Polylactic acid (PLA) is a transparent plastic produced from corn[12] or dextrose. It not only resembles conventional petrochemical-based mass plastics (like PET, PS or PE) in its characteristics, but it can also be processed on standard equipment that already exists for the production of some conventional plastics. 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.

Poly-3-hydroxybutyrate (PHB)[edit]

The biopolymer poly-3-hydroxybutyrate (PHB) is a polyester produced by certain bacteria processing glucose, corn starch[13] or wastewater.[14] Its characteristics are similar to those of the petroplastic polypropylene. 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 produces transparent film at a melting point higher than 130 degrees Celsius, and is biodegradable without residue.

Polyhydroxyalkanoates (PHA)[edit]

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 (PA 11)[edit]

PA 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 (PA 410), derived 70% from castor oil, under the trade name EcoPaXX, commercialized by DSM.[15] PA 410 is a high-performance polyamide that combines the benefits of a high melting point (approx. 250°C), low moisture absorption and excellent resistance to various chemical substances.

Bio-derived polyethylene[edit]

The basic building block (monomer) of polyethylene is ethylene. This is just one small chemical step 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. It can also considerably reduce greenhouse gas emissions. Brazilian chemicals group Braskem claims that using its route from sugar cane ethanol to produce one tonne of polyethylene captures (removes from the environment) 2.5 tonnes of carbon dioxide while the traditional petrochemical route results in emissions of close to 3.5 tonnes.

Braskem plans to introduce commercial quantities of its first bio-derived high density polyethylene, used in a packaging such as bottles and tubs, in 2010 and has developed a technology to produce bio-derived butene, required to make the linear low density polyethylene types used in film production.[16]

Genetically modified bioplastics[edit]

Genetic modification (GM) is also a challenge for the bioplastics industry. None of the currently available bioplastics – which can be considered first generation products – require the use of GM crops, although GM corn is the standard feedstock.

Looking further ahead, some of the second generation bioplastics manufacturing technologies under development employ the "plant factory" model, using genetically modified crops or genetically modified bacteria to optimise efficiency.

Environmental impact[edit]

Confectionery packaging made of PLA-blend bio-flex
Bottles made from cellulose acetate biograde
Drinking straws made of PLA-blend bio-flex
Jar made of PLA-blend bio-flex, a bioplastic

The environmental impact of bioplastics is often debated, as there are many different metrics for "greeness" (e.g. water use, energy use, deforestation, biodegredation etc) and tradeoffs often exist.[17] The debate is also complicated by the fact that many different types of bioplastics exist, each with different environmental strengths and weaknesses, so not all bioplastics can be treated as equal.

The production and use of bioplastics is sometimes regarded as a more sustainable activity when compared with plastic production from petroleum (petroplastic), because it relies less on fossil fuel as a carbon source and also introduces fewer, net-new greenhouse emissions if it biodegrades. They significantly reduce hazardous waste caused by oil-derived plastics, which remain solid for hundreds of years, and open a new era in packing technology and industry.[18]

However, manufacturing of bioplastic materials is often still reliant upon petroleum as an energy and materials source. This comes in the form of energy required to power farm machinery and irrigate growing crops, to produce fertilisers and pesticides, to transport crops and crop products to processing plants, to process raw materials, and ultimately to produce the bioplastic, although renewable energy can be used to obtain petroleum independence.

Italian bioplastic manufacturer Novamont[19] states in its own environmental audit[20] that producing one kilogram of its starch-based product uses 500 g of petroleum and consumes almost 80% of the energy required to produce a traditional polyethylene polymer. Environmental data from NatureWorks,[21][22] the only commercial manufacturer of PLA (polylactic acid) bioplastic, says that making its plastic material delivers a fossil fuel saving of between 25 and 68 per cent compared with polyethylene, in part due to its purchasing of renewable energy certificates for its manufacturing plant.

A detailed study examining the process of manufacturing a number of common packaging items in several traditional plastics and polylactic acid carried out by Franklin Associates and published by the Athena Institute shows the bioplastic to be less environmentally damaging for some products, but more environmentally damaging for others.[23] This study however does not consider the end-of-life of the products, thus ignores the possible methane emissions that can occur in landfill due to biodegradable plastics.

While production of most bioplastics results in reduced carbon dioxide emissions compared to traditional alternatives, there are some real concerns that the creation of a global bioeconomy could contribute to an accelerated rate of deforestation if not managed effectively. There are associated concerns over the impact on water supply and soil erosion.

Other studies showed that bioplastics represent a 42% reduction in carbon footprint.[24]

On the other hand, bioplastic can be made from agricultural byproducts[18] and also from used plastic bottles and other containers using microorganisms.[25]

On October 21, 2010, a group of scientists reported that corn-based plastic ranked higher in environmental defects than the main products it replaces, such as HDPE, LDPE and PP. In the study, corn-based plastics created more acidification, carcinogens, ecotoxicity, eutrophication, ozone depletion, respiratory effects and smog than the synthetic-based plastics they replaced.[26]. However the study also concluded that biopolymers trumped the other plastics for biodegradability, low toxicity, and use of renewable resources.

The American Carbon Registry has also released reports of nitrous oxide caused from corn growing which is 310 times more potent than CO2. Pesticides are also used in growing corn-based plastic.[27]

Bioplastics and biodegradation[edit]

Packaging air pillow made of PLA-blend bio-flex

The terminology used in the bioplastics sector is sometimes misleading. Most in the industry use the term bioplastic to mean a plastic produced from a biological source. All (bio- and petroleum-based) plastics are technically biodegradable, meaning they can be degraded by microbes under suitable conditions. However many degrade at such slow rates as to be considered non-biodegradable. Some petrochemical-based plastics are considered biodegradable, and may be used as an additive to improve the performance of many commercial bioplastics.[28] Non-biodegradable bioplastics are referred to as durable. The degree of biodegradation varies with temperature, polymer stability, and available oxygen content. Consequently, most bioplastics will only degrade in the tightly controlled conditions of industrial composting units. In compost piles or simply in the soil/water, most bioplastics will not degrade (e.g. PH), starch-based bioplastics will, however.[29] The European standard, EN13432, defines how quickly and to what extent a plastic must be degraded under industrial composting conditions for it to be called compostable. This is published by the International Organization for Standardization ISO and is recognized in many countries, including all of Europe, Japan and the US. However, it is designed only for the aggressive conditions of industrial composting units at or above 140F. There is no standard applicable to home composting conditions.

The term "biodegradable plastic" has also been used by producers of specially modified petrochemical-based plastics which appear to biodegrade.[30] Biodegradable plastic bag manufacturers that have misrepresented their product's biodegradability may now face legal action in the US state of California for the misleading use of the terms biodegradable or compostable.[31] Traditional plastics such as polyethylene are degraded by ultra-violet (UV) light and oxygen. To prevent this, process manufacturers add stabilising chemicals. However with the addition of a degradation initiator to the plastic, it is possible to achieve a controlled UV/oxidation disintegration process. This type of plastic may be referred to as degradable plastic or oxy-degradable plastic or photodegradable plastic because the process is not initiated by microbial action. While some degradable plastics manufacturers argue that degraded plastic residue will be attacked by microbes, these degradable materials do not meet the requirements of the EN13432 commercial composting standard. The bioplastics industry has widely criticized oxo-biodegradable plastics, which the industry association says do not meet its requirements. Oxo-biodegradable plastics – known as "oxos" – are conventional petroleum-based products with some additives that initiate degradation. The ASTM standard used by oxo producers is just a guideline. It requires only 60% biodegradation, P-Life is an oxo plastic claiming biodegradability in soil at a temperature of 23 degrees Celsius reaches 66% after 545 days. Dr Baltus of the National Innovation Agency, has said that there is no proven evidence that bio-organisms are really able to consume and biodegrade oxo plastics.

Recycling[edit]

There are also concerns that bioplastics will damage existing recycling projects. Packaging such as HDPE milk bottles and PET water and soft drinks bottles is easily identified and hence setting up a recycling infrastructure has been quite successful in many parts of the world, although only 27% of all plastics actually get recycled.[32] However, plastics like PET do not mix with PLA, yielding unusable recycled PET if consumers fail to distinguish the two in their sorting. The problem could be overcome by ensuring distinctive bottle types or by investing in suitable sorting technology. However, the first route is unreliable, and the second costly.

Market[edit]

Tea bags made of polylactide (PLA), (peppermint tea)
Prism pencil sharpener 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.[33] In contrast, global consumption of all flexible packaging is estimated at around 12.3 million tonnes.[34]

COPA (Committee of Agricultural Organisation in the European Union) and COGEGA (General Committee for the Agricultural Cooperation in the European Union) have made an assessment of the potential of bioplastics in different sectors of the European economy:

Catering products: 450,000 tonnes per year
Organic waste bags: 100,000 tonnes per year
Biodegradable mulch foils: 130,000 tonnes per year
Biodegradable foils for diapers 80,000 tonnes per year
Diapers, 100% biodegradable: 240,000 tonnes per year
Foil packaging: 400,000 tonnes per year
Vegetable packaging: 400,000 tonnes per year
Tyre components: 200,000 tonnes per year
Total: 2,000,000 tonnes per year

In the years 2000 to 2008, worldwide consumption of biodegradable plastics based on starch, sugar, and cellulose – so far the three most important raw materials – has increased by 600%.[35] The NNFCC predicted global annual capacity would grow more than six-fold to 2.1 million tonnes by 2013.[33] BCC Research forecasts the global market for biodegradable polymers to grow at a compound average growth rate of more than 17 percent through 2012. Even so, bioplastics will encompass a small niche of the overall plastic market, which is forecast to reach 500 billion pounds (220 million tonnes) globally by 2010.[36]

Cost[edit]

At one time bioplastics were too expensive for consideration as a replacement for petroleum-based plastics. The lower temperatures needed to process bioplastics and the more stable supply of biomass combined with the increasing cost of crude oil make bioplastics' prices [37] more competitive with regular plastics.

Research and development[edit]

Bioplastics Development Center - University of Massachusetts Lowell
A pen made with bioplastics (Polylactide, PLA)
  • In the early 1950s, amylomaize (>50% amylose content corn) was successfully bred and commercial bioplastics applications started to be explored.
  • In 2004, NEC developed a flame retardant plastic, polylactic acid, without using toxic chemicals such as halogens and phosphorus compounds.[38]
  • In 2005, Fujitsu became one of the first technology companies to make personal computer cases from bioplastics, which are featured in their FMV-BIBLO NB80K line. Later, the French company Ashelvea (also listed on EU Energy Star registered partners), launched its fully recyclable PC with biodegradable plastic case "Evolutis", reported in "People Inspiring Philips", a series of 3 mini-documentaries to inspire Philips employees with some examples from the civil society.[39][40]
  • In 2007 Braskem of Brazil announced it had developed a route to manufacture high density polyethylene (HDPE) using ethylene derived from sugar cane.
  • In 2008, a University of Warwick team created a soap-free emulsion polymerization process which makes colloid particles of polymer dispersed in water, and in a one step process adds nanometre sized silica-based particles to the mix. The newly developed technology might be most applicable to multi-layered biodegradable packaging, which could gain more robustness and water barrier characteristics through the addition of a nano-particle coating.[41]

Testing procedures[edit]

A bioplastic shampoo bottle made of PLA-blend bio-flex

Industrial compostability – EN 13432, ASTM D6400[edit]

The EN 13432 industrial standard is arguably the most international in scope and compliance with this standard is required to claim that a product is compostable in the European marketplace. In summary, it requires biodegradation of 90% of the materials in a lab within 90 days. The ASTM 6400 standard is the regulatory framework for the United States and sets a less stringent threshold of 60% biodegradation within 180 days, unless it is a homopolymer, then it would need to be 90%, again within industrial composting conditions, where the facility is at or above 140F. Municipal compost facilities do not see above 130F.[citation needed]

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[edit]

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."[42]

This definition drew much criticism for the fact that, contrary to the way the word is traditionally defined, it completely divorces the process of "composting" from the necessaity of it leading to humus/compost as the end product. Indeed, the only criteria this standard does describe is that a compostable plastic must look to be going away as fast as something else we have already established to be compostable under the traditional definition.

Withdrawal of ASTM D 6002[edit]

In January 2011, the ASTM withdrew standard ASTM D 6002, which is what 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."[43]

The ASTM has yet to replace this standard.

Biobased – ASTM D6866[edit]

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 (solid or liquid) can be measured with an accelerator mass spectrometer.[44][45]

There is an important difference between biodegradability and biobased content. A bioplastic such as high density polyethylene (HDPE)[46] can be 100% biobased (i.e. contain 100% renewable carbon), 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[edit]

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.

Legal implications[edit]

In 2012 the Attorney General of Vermont sued a BPI certified product claiming "compostable plastic" for false claims, these claims were made under the pretense that industrial compost facilities existed by BPI, through further examination these industrial compost facilities were nowhere to be found.[47]

See also[edit]

References[edit]

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  2. ^ Hong Chua1, Peter H. F. Yu, and Chee K. Ma (March 1999). "Accumulation of biopolymers in activated sludge biomass". Applied Biochemistry and Biotechnology (Humana Press Inc.) 78: 389–399. doi:10.1385/ABAB:78:1-3:389. ISSN 0273-2289. Retrieved 2009-11-24. 
  3. ^ Chen, G. , & Patel, M. (2012). Plastics derived from biological sources: Present and future: P technical and environmental review. Chemical Reviews, 112(4), 2082-2099.
  4. ^ "Terminology for biorelated polymers and applications (IUPAC Recommendations 2012)". Pure and Applied Chemistry 84 (2): 377–410. 2012. doi:10.1351/PAC-REC-10-12-04. 
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External links[edit]