BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE AND/OR ...BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE...

BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE AND/OR BIODEGRADABLE ALTERNATIVES TO PETROPLASTICS

1. Introduction

‘‘Plastics’’ were introduced approximately 100 years ago, and today are one of the most used and most versatile materials. Yet society is fundamentally ambivalent toward plastics, due to their environmental implications, so interest in bioplastics has sparked.

According to the petrochemical market information provider ICIS, ‘‘The emergence of bio-feedstocks and bio-based commodity polymers production, in tandem with increasing oil prices, rising consumer consciousness and improving economics, has ushered in a new and exciting era of bioplastics commercialization. However, factors such as economic viability, product quality and scale of operation will still play important roles in determining a bioplastic’s place on the commercialization spectrum’’ (1).

The annual production of synthetic polymers (‘‘plastics’’), most of which are derived from petrochemicals, exceeds 300 million tons (2), having replaced traditional materials such as wood, stone, horn, ceramics, glass, leather, steel, concrete, and others. They are multitalented, durable, cost effective, easy to process, impervious to water, and have enabled applications that were not possible before the materials’ availability.

Plastics, which consist of polymers and additives, are defined by their set of properties such as hardness, density, thermal insulation, electrical isolation, and primarily their resistance to heat, organic solvents, oxidation, and microorganisms. There are hundreds of different plastics; even within one type, various grades exist (eg, low viscosity polypropylene (PP) for injection molding, high viscosity PP for extrusion, and mineral-filled grades).

Applications for polymeric materials are virtually endless; they are used as construction and building material, for packaging, appliances, toys, and furniture, in cars, as colloids in paints, and in medical applications, to name but a few. Plastics can be shaped into films, fibers, tubes, plates, and objects such as bottles or boxes. They are sometimes the best available technology. Many plastic products are intended for a short-term use, and others have long-term applications (eg, plastic pipes, which are designed for lifetimes in excess of 100 yr).

On the other hand, there is a growing debate about crude oil depletion and price volatility, and environmental concerns with plastics are becoming more serious. Approximately half of all synthetic polymers end up in short-lived products, which are partly thermally recycled (burnt), but to some extent end up on landfills or, worse, in the oceans, where large plastic objects are washed ashore, sink or float (eg, the ‘‘North Pacific Garbage Patch,’’ which has continental dimensions), and get fragmented to ‘‘microplastics’’ (particles between a few mm and <5 mm) that harm and kill various organisms, finally ending up on our plates. It is estimated that globally some 900 billion plastic bags (shopping bags, waste bags, etc) are produced each year, with a typical average useful life of only a few minutes and a significant fraction of them ending up as litter in the environment (3), having wasted energy, spoiling the scene, and seriously harming wildlife.

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Kirk-Othmer Encyclopedia of Chemical Technology. Copyright # 2015 John Wiley & Sons, Inc. All rights reserved. DOI: 10.1002/0471238961.koe00006

http://dx.doi.org/10.1002/0471238961.koe00006

2 BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE

It is estimated that since the 1950s, approximately 1 billion tons of plastics have been discarded and some of that material might persist for centuries or even significantly longer, as it is demonstrated by the persistence of natural materials such as amber (4).

One of the biggest advantages of plastics, their durability, is likewise one of their biggest problems: The rate of degradation (biodegradation) does not match their intended service life, and buildup in the environment occurs.

Recycling of waste plastics, in principle, a meaningful approach, can follow different routes:

1. Reuse of the product (eg, a bag). 2. Material recycling (collection, sorting, and reprocessing). 3. Feedstock recycling (depolymerization to capture the monomers). 4. Thermal recycling (use of the energy content in waste incineration, steel

works, or cement kilns).

Recycling plastics is not always feasible, and it can have a negative eco- balance due to the efforts for collecting, sorting, and processing them. In most cases, they need to be washed, and waste grinding and processing are energy consuming. The recycling rate of plastics differs from country to country; there are also differences in the plastics concerned. In the United States, the recycling rate for polyethylene terephthalate (PET) packaging (bottles) was 31.2% in 2013 (5). PET has the highest value of commodity plastics and is used mainly for drinking bottles; hence, efforts are made to collect it. Recycled plastics go through different processing steps such as sorting and melt filtration. They can often only be used in lower grade products, typically not with direct food contact or high performance applications. A ‘‘usage cascade’’ can be created, ending in thermal recycling (combustion: incineration or pyrolysis).

To summarize, the extensive use of plastics has become a problem in many aspects. Therefore, growing interest in ‘‘bioplastics’’ is observed (for reuse and recycling of bioplastics, an unsolved issue, see Reference 6 and Section 9).

The term ‘‘bioplastics’’ stands for ‘‘biobased polymers.’’ According to IUPAC, a bioplastic is derived from ‘‘biomass or . . . monomers derived from the biomass and which, at some stage in its processing into finished products, can be shaped by flow’’ (7).

In the area of bioplastics, several terms are used vaguely, ambiguously, or wrongly. Hence, some important definitions are provided as follows (see also Reference 7).

Plastics (plastic materials) in general are a huge range of organic solids that are malleable (pliable, moldable). Malleability is a material’s ability to deform under compressive stress. Plastics usually consist of organic polymers with high molecular weight and other substances (fillers, colors, and additives). They are typically synthetically produced. The term ‘‘natural plastics’’ is sometimes used in the industry for unfilled and uncolored plastics, as opposed to compounds.

BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE 3

Often, the expression bioplastics is used to make a distinction from polymers derived from fossil resources (monomers). The term is, to some extent, misleading,


--

as the prefix ‘‘bio’’ suggests that any polymer derived from biomass is environment-friendly.

Biobased polymers are neither necessarily biocompatible nor biodegradable. According to industry association European Bioplastics, bioplastics are

‘‘polymers that are biobased, biodegradable, or both’’ (8). So the industry has adopted a rather large definition. An alternative expression could be ‘‘technical biopolymers.’’

In case polymers are obtained from agro-resources such as polysaccharides (eg, starch) (9), one can talk about ‘‘agro-polymers.’’

‘‘Biomaterials’’ denote materials that are exploited in contact with living tissues, organisms, or microorganisms. Hence, ‘‘polymeric biomaterials’’ are used in applications such as medicine (catheters, bone cements, and contact lenses) (10). Many of them are conventionally produced polymers. Implantable biomaterials are PET, PP, PEEK (polyetheretherketone), UHMWPE (ultrahigh molecular weight polyethylene), and PTFE (polytetrafluoroethylene) (11,12), on the one hand, and (bio-)resorbable polymersPGA (polyglycolide), PLA (polylactide), PCL (polycaprolactone), and PGS (poly(glycerol sebacate)), on the other hand (12,13).

Generally, a polymer is a substance composed of macromolecules. A macromolecule is a very large molecule commonly made by polymerization

of smaller subunits. In biochemistry, the term is applied to the main biopolymers such as nucleic acids (eg, DNA), proteins, and carbohydrates (natural polymers), plus other large, nonpolymeric molecules such as lipids and polyphenols. Natural polymers (‘‘biopolymers’’) can be organic or inorganic (14), the latter having a skeleton devoid of carbon (15). Examples for the former include cellulose, starch, latex, and chitin; examples for the latter include polyphosphazenes, polysilicates, polysiloxanes, polysilanes, polysilazanes, polygermanes, and polysulfides. In between, one can find so-called hybrid polymers, ie, polymers containing inorganic and organic components such as polydimethylsiloxane (silicone rubber: --[O--Si (CH3)2]n ).

Synthetic polymers (artificial polymers) are man-made polymers. They are built from monomers by polymerization, polycondensation, or polyaddition. Most synthetic polymers have significantly simpler and more random (stochastic) structures than natural ones. They show a molecular mass distribution, which does not exist in biopolymers (polydispersity vs monodispersity). They are substances that are not produced by nature (xenobiotics). Due to their high molecular weight, they are not mobile. From a practical processing point of view, synthetic polymers can be classified into the four main categories: thermoplastics (thermo- softening plastics), thermosets (duromers), elastomers, and synthetic fibers. The most common synthetic polymers are

• polyethylene (PE: PE-HD and PE-LD, with HD being high density and LD

being low density); • polypropylene; • acrylonitrile–butadiene–styrene (ABS); • polyethylene terephthalate;


• polycarbonate (PC);


Fig. 1. Typical applications of polymers. The sizes of the bubbles show the relative importance. PS-E ¼ expanded PS; ASA ¼ acrylonitrile–styrene–acrylate; SAN ¼ styrene– acrylonitrile; other eng. ¼ other engineering plastics. (Source: Reference 2.)

• polyvinyl chloride (PVC); • polystyrene (PS); • polyamides (PAs, eg, Nylon 6 and Nylon 66); • Teflon (polytetrafluoroethylene); • polyurethane (PU, PUR); • poly(methyl methacrylate) (PMMA, acrylic).

They are nonbiodegradable. Note: Technically, all conventional plastics are degradable. However, due to their slow breakdown, they are considered practi- cally non(bio)degradable.

Typical applications of polymers are shown in Figure 1. Semi-synthetic polymers are chemically treated polymers of natural origin.

An example is rubber. It is made from latex, the ‘‘milk’’ of Hevea brasiliensis (rubberwood), by vulcanizing it (cross-linking the polymer chains to a certain extent) using sulfur or S2Cl2. Another example is cellulose. Cellulose can be modified in two different ways:

• It can be dissolved and precipitated again in a different physical shape, eg, to

produce viscose silk (rayon), using CS2. • It can be chemically modified, using the three remaining OH groups of the

glucose monomers, eg, to cellulose acetate (CA) with acetic acid, cellulose


methyl ethers with methanol, and cellulose nitrate with nitric acid.


-- -- --

-- -- ---- --

-- --

Table 1. Typical Bonds in Polymers

Type of bond Natural examples Synthetic examples carbon–carbon ( C C ) polyolefins (eg, rubber) polyolefins (eg, polyethylene,

polypropylene) ester ( O C O ) nucleic acids (eg, DNA, RNA) polyesters (eg, Diolen, a

polyester fiber) amide (--C----O--NH--) polypeptides (eg, wool, silk,

ether ( O ) polysaccharides (eg, starch,

cellulose)

Modified from Ref. 16. POM ¼ polyoxymethylene.

polyamides (eg, Nylon, a polyamide)

special plastics (eg, DuPont’s Delrin, a POM)

Thus, a ‘‘synthetic biopolymer’’ refers to a man-made biopolymer that is

prepared using abiotic chemical routes. Table 1 shows the bonds in polymers. Two common processing technologies for the economically important ther-

moplastics are extrusion (continuous process, yielding, eg, window profiles or pipes) and injection molding (batch process, yielding, eg, dishes and cups).

Polymers (‘‘plastics’’) can be blended (17) and further processed to compounds and composite materials with different properties. Examples include flame-retardant or colored polypropylene, talc-filled polypropylene (eg, for reduced thermal expansion in bumpers), NFRPs (natural fiber-reinforced plastics), and WPCs (wood plastic composites or wood polymer composites, ie, wood fibers in a polymer such as PE or PVC). NFRPs are used in automobiles, construction and furniture, and industrial and consumer products. Applications of WPCs are deckings, railings, window and door frames, and furniture; the main market is currently in the United States. For composites and nanocomposites based on cellulose, see, eg, Reference 18.

2. Motivation for and Types of Bioplastics

After food and textiles, the ‘‘organic trend’’ is continuing to spread into materials; bioplastics have come en vogue and receive extensive media attention, although current production volumes are only on the order of 1% of annual plastics manufacturing.

Increasing oil prices, rising consumer consciousness and environmental awareness, improving feedstock and process economics, better product quality, and scale of operation have helped ‘‘revive’’ bioplastics (see Section 5).

Other factors that motivate R&D in bioplastics are as follows:

• Rural development: added value and jobs (bioplastics feedstock is typically grown in rural areas, where farmers can benefit).

• Interesting new properties or mix of properties (degradability, haptics, weight, etc).

• Feedstock diversification (less dependence on crude oil, which is finite).

enzymes)


Growth rates of bioplastics in excess of 20–30% have been witnessed for several years and several materials. These are expected to continue. There is a

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BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE

- - - - - - - þþþ

Table 2. Bioplastics Intermaterial Substitution Opportunities

Polyolefins Other polymers

PHA þ þ þþ þþ þþ - - þþ

other polyesters þþ þþ þþþ þþþ þþ þ þþ þþ

þþþ þþ þþþ - - - - -

Source: Chemical Market Resources, Inc. (20). LDPE, HDPE: low-, high-density PE; PUR: polyurethane; PLA: polylactic acid; PHA: polyhydroxyalkanoates; substitution potential: (þþþ) high, (þþ) medium, (þ) low, and (-) not foreseen.

substitution potential of up to 90% of the total consumption of plastics by biobased polymers (19). This concerns standard polymers such as PE, PP, PVC, and PET, as well as high performance polymers such as PAs (see Table 2).

Bioplastics have two aspects: ‘‘green’’ educt and/or ‘‘green’’ product (where ‘‘green’’ stands for ‘‘sustainable’’):

• Use of a ‘‘green’’ feedstock for the production of conventional polymers (so-

called drop-in polymers): renewability. • Synthesis of ‘‘green’’ polymers: biodegradability.

This is illustrated in Figure 2. As Figure 2 shows, a material that is either renewable or biodegradable qualifies as biopolymer. There are also ‘‘partly biobased’’ biodegradable and nonbiodegradable biopolymers, if, for instance, only one blending partner or only part of the feedstock is derived from renewable resources (see Table 3).

The content of biobased carbon can be determined by radiocarbon analysis according to ISO 16620 and ASTM D6866-05 (22,23). The measurement has a high accuracy. In this context, one can also talk about ‘‘hybrid’’ plastics (not to be confused with those plastics that contain inorganic and organic components).

As can be seen from Figure 2 and Table 3, bioplastics can be renewable and/or degradable. They can contribute to sustainability (24) at ‘‘the cradle,’’ at ‘‘the grave,’’ or both. The box in the bottom left of Figure 2 is ‘‘conventional plastics,’’ whereas the other three boxes can be considered biobased polymers. The distinction, due to the two dimensions, is somewhat blurred, since many plastics on the market contain bioplastics to a certain extent in blends with conventional polymers.

Degradable bioplastics are intended for short-lived, disposable products. Biobased durable plastics are to replace conventionally produced plastic goods.

A bioplastic material can also fulfill both criteria. Polylactic acid, thermoplastic starches (TPS), and polyhydroxyalkanoates (PHAs) are based on natural/ renewable feedstock and exhibit biodegradation under various conditions. Prod- ucts such as biobased polyamides and biopolyethylene are fabricated from bio- derived feedstocks but are not degradable. On the other hand, polybutylene

biobased-PE

LDPE LLDPE HDPE PP PS PVC PUR PET starch polymers PLA

þþ þþ þþ þþ þ - þþ -


terephthalate (PBT) and polybutylene succinate (PBS) are typically manufactured from petrochemical feedstocks but are biodegradable.

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Fig. 2. Types of bioplastics, both biodegradable and nonbiodegradable, and examples. (Reprinted with permission from Reference 21. # 2013, Elsevier.)

Table 3. Biodegradable vs Biobased Polymers

Biodegradable Nonbiodegradable biobased CA, CAB, CAP, CN, PHB, PHBV,

PLA, starch, chitosan partially biobased PBS, PBAT, PLA blends, starch

blends fossil fuel-based PBS, PBSA, PBSL, PBST, PCL,

PGA, PTMAT, PVOH

PE (LDPE), PA 11, PA 12, PET, PTT

PBT, PET, PTT, PVC, SBR, ABS, PU, epoxy resin

PE (LDPE, HDPE), PP, PS, PVC, ABS, PBT, PET, PS, PA 6, PA 6.6, PU, epoxy resin, synthetic rubber

Source: Ref. 6. Abbreviations: ABS, acrylonitrile–butadiene–styrene; CA, cellulose acetate; CAB, cellulose acetate butyrate; CAP, cellulose acetate propionate; CN, cellulose nitrate; HDPE, high density polyethylene; LDPE, low density polyethylene; PA 6, polyamide 6; PA 6.6, polyamide 6.6; PA 11, aminoundecanoic acid-derived polyamide; PA 12, laurolactam-derived polyamide; PBAT, poly (butylene adipate-co-terephthalate); PBS, polybutylene succinate; PBSA, poly(butylene succinate-co- adipate); PBSL, poly(butylene succinate-co-lactide); PBST, poly(butylene succinate-co-terephthalate); PBT, polybutylene terephthalate; PCL, poly(e-caprolactone); PE, polyethylene; PET, polyethylene terephthalate; PGA, polyglycolide; PHB, polyhydroxybutyrate; PHBV, poly(3- hydroxybutyrate-co-3-hydroxyvalerate); PLA, polylactide; PP, polypropylene; PS, polystyrene;


PTMAT, poly(methylene adipate-co-terephthalate); PTT, polytrimethylene terephthalate; PVOH, polyvinyl alcohol; PVC, polyvinyl chloride; PU, polyurethane; SBR, styrene–butadiene rubber.

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Bioplastics can reduce carbon dioxide emissions by 30–70% compared with conventional plastics (19).

‘‘Green chemistry’’ (or sustainable chemistry) can be understood as the design of chemical products and processes that reduce or eliminate the use or generation of substances that are hazardous to humans, animals, plants, and the environment, where energy efficiency should be high and the waste target is zero; as a consequence, costs should also be low. A ‘‘green polymer’’ is one that conforms to the concept of green chemistry. Note, however, that a green polymer does not necessarily mean ‘‘environment-friendly polymer’’ or ‘‘biobased polymer.’’

So the motivation for bioplastics is sustainability. The principle for sustainability is simply explained: Whatever man needs for survival and well-being directly and indirectly comes from our natural environment. Sustainable action is one that maintains conditions under which humans and nature coexist harmoni- ously and where social, economic, and environmental requirements of present and future generations are met.

3. Sustainability of Plastics and Bioplastics

A discussion of sustainability of plastics has to consider two main aspects: life cycle assessment (LCA) and ecotoxicity. LCA, also referred to as eco-balance and cradle-to-grave analysis, is the investigation and valuation of the environmental impacts of a given product or service over its entire existence (input, life, and output), considering raw material sourcing, production process, packaging, distribution, usage, and waste management including transport (25). For details, see, eg, the standards ISO 14040 and ISO 14044.

Ecotoxicity subsumes the consequence of adverse effects caused by a substance on the environment and on living organisms. The environment encom- passes water, air, and soil. When only living organisms such as animals, plants, and microorganisms are affected, the term ‘‘toxicity’’ should be used.

Pure plastics generally show low toxicity due to their insolubility in water and since they are biochemically inert (because of a large molecular weight). Plastic products, in contrast, contain a variety of additives, some of which can be toxic (eg, phthalates as plasticizers). Also, residues of toxic monomers can still

exist in the product (eg, vinyl chloride, the precursor of PVC, a human carcinogen), or it can release such monomers or oligomers upon excessive heating (eg, PTFE).

Toxic substances can further be produced during incineration, particularly when it is carried out in an uncontrolled way (at low temperatures, dioxins, PAHs (polycyclic aromatic hydrocarbons), and other noxious fumes can be formed).

An increasing presence of microplastics was found in the marine food chain. Microplastics (debris <5 mm) can occur in the environment as primary or secondary microplastics (26). Primary microplastics are those manufactured for a specific purpose, eg, for cosmetic products. Secondary microplastics are those produced through environmental fragmentation of larger-sized products. Their typical abundance was reviewed in Reference 26 (see Table 4).

In a recent study of microplastics in bivalves cultured for human consump-


tion, it was found that the two species investigated contained on average 0.36 and 0.47 particles/g, which exposes the European shell fish consumer to an estimated

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Table 4. Spatial Distribution and Abundance of Microplastics from Selected References

Location Maximum concentration observed, particles/km2

Italy, Lake Garda 1,108,000,000 Portugal, beach 218,000,000 northwestern Mediterranean Sea 1,000,000 USA, Laurentian Great Lakes 466,000 waters around Australia 839

Modified with permission from Ref. 26. # 2015, Elsevier.

11,000 microplastic particles per year (27). For images of microplastics ingested by various animals, see, eg, the Swiss exhibition ‘‘Plastics Garbage Project’’ (28).

3.1. Environmental Aspects of Plastics. Major environmental aspects of plastics include raw material consumption, energy use (29), and

pollution. Before the ban of CFCs (chlorofluorocarbons), the production of foamed polystyrene (expanded polystyrene (EPS) and extruded polystyrene (XPS)) has contributed to the destruction of the ozone layer. The production of plastics is a

rather energy-intensive process (29,30). Recycling of plastics is mostly impeded by the lack of efficient sorting techniques. Apart from combustion, pyrolysis into

hydrocarbon fuels is feasible, but not yet carried out on an industrial level. As for the effect of plastics on climate change (31), there is a mixed contribution;

petroplastics that are burnt (‘‘thermal recycling’’ into electricity and heat at waste-to-energy plants) release CO2 into the atmosphere. In long-term applica-

tions and on landfills (which is increasingly banned, though), they become carbon sinks. Over their useful life, lightweight plastics can help reduce transportation emissions, eg, when used in cars instead of heavier materials, or when being deployed as packaging material as opposed to glass or metal. For instance, it was estimated that packaging beverages in PET bottles rather than glass bottles or metal cans will save 52% of transportation energy (32). According to industry association Plastics Europe, 5% less weight in a car translates on average into fuel savings of 3%. Life cycle assessments are necessary to find the net contribution.

Plastics are generally perceived less environment-friendly than other materials such as paper, concrete, steel, and aluminum, partly due to lobbying activities (33,34).

3.2. Plastics: Pros and Cons. Plastics and bioplastics in particular do have several advantages. Table 5 provides a list of major pros and cons.

An environmental preference spectrum for plastics, exemplarily worked out for the healthcare industry, is shown in Figure 3.

One can see from Figure 3 that bioplastics are assessed as most preferential from an environmental point of view. The sustainability enhancement of bioplastics over conventional petrochemical-based plastics is depicted in Table 6.

Main sustainability drivers are energy savings and greenhouse gas emission cuts, apart from biodegradability and compostability. The environmental and occupational health and safety hazards of biobased plastics are discussed in Table 7.

The environmental impacts of biobased plastics are discussed in Table 8.


Table 9 presents a comparison of a bioplastic (polyhydroxybutyrate (PHB)) with a conventional commodity polymer (PP) in 10 categories (see also Table 8).


Table 5. Pros and Cons of Petrobased and Biobased Plastics

Pros Cons conventional

plastics

bioplastics (compared with conventional plastics)

• low cost • good and excellent technical

properties • easy processability • can save energy and resources

compared with other materials, depending on application

• thermal recycling possible (cascade use)

• (partly) biodegradable • (partly) based on natural

feedstock, hence reducing the emission of GHG and the dependence on crude oil

• interesting properties • generally, standard

manufacturing processes and plants can be used for biobased feedstock, and standard processing machines can be used for biobased plastics

• based on petrochemicals • difficult to recycle • mostly not biodegradable • uncontrolled combustion can

release toxic substances • ecotoxicity, particularly

microplastics in the marine environment

• partly toxic raw materials and additives

• costly • (partly) use of genetically

modified organisms • use of land, fertilizers, and

pesticides for crops, potential food competition

• narrow processing window (lower melting temperature)

• brittleness • thermal degradation

• positive image among consumers

‘‘CML 2 Baseline 2000 V2.03’’ mentioned in Table 9 is a database that contains characterization factors for life cycle impact assessment (LCIA). It is available at the University of Leiden (37).

It is found in this study that, in all of the life cycle categories, PHB is superior to PP. Energy requirements are slightly lower than those for polyolefin production. PE impacts are lower than PHB values in acidification and eutrophication (36).


Fig. 3. Environmental preference spectrum for the healthcare industry. (Reprinted with permission from Reference 35. # 2012, Elsevier.)


Table 6. Sustainability Improvements of Biobased Plastics Relative to Petroleum-Based Plastics (PBP)

Bioplastic Sustainability improvement polyhydroxyalkanoates highly biodegradable polylactic acid production uses 30–50% less fossil energy and

generates 50–70% less CO2 emissions than PBP; competitive use of water with the best performing PBP, recyclable, compostable at temperatures above 600C

thermoplastic starch production requires 68% less energy than its PBP counterpart; lower CO2 emissions than PBP; biodegradable and compostable

biourethanes production requires 23% less energy and 36% less GGH, compared with PBP

cellulose and lignin the biological degradation of lignin is lower than cellulose, compostable

polytrimethylene terephthalate production requires 26–50% less energy and 44% lower GHG than its PBP counterpart; no chemicals additives are used; biodegradable; potentially recyclable

Corn zein and soy protein biodegradable and compostable

Source: Ref. 35. GMOs: genetically modified organisms; GHG: greenhouse gases.

Table 7. Environmental and Occupational Health and Safety Hazards of Biobased Plastics

Bioplastic Environmental hazards Occupational health and safety hazards polyhydroxyalkanoates feedstock is grown using

methods of industrial agricultural production, including GMOs; data on energy requirements are controversial

polylactic acid feedstock is grown using

methods of industrial agricultural production, including GMOs; 1-octanol is ecotoxic and organic tin can build up in living organisms

thermoplastic starch feedstock is grown using methods of industrial agricultural production, including GMOs

biourethanes (BURs) feedstock is grown using methods of industrial agricultural production, including GMOs

cellulose and lignin the process has relatively high

energy and water

requirements; emissions of


exposure to pesticides; physical extraction of PHAs uses pyridine, methanol, hexane, or diethyl ether; chemical digestion uses sodium hypochlorite, methanol, and diethyl ether

exposure to pesticides, sulfuric acid, tin octoate, 1-octanol, and urea; finely pulverized starch can cause powerful explosions

exposure to pesticides, glycerol, and urea; finely

pulverized starch can cause powerful explosions exposure to pesticides, toluene diisocyanate (TDI),

methylene diphenyl isocyanate (MDI), tin derivatives

exposure to elevated temperature and pressure; exposure to disulfide, sodium

(continued)


Table 7. (Continued)

Bioplastic Environmental hazards Occupational health and safety hazards

polytrimethylene terephthalate

corn zein and soy protein

nanobiocomposites (cellulose and lignin)

pollutants to air and water during kraft process need to be addressed

feedstock is grown using methods of industrial agricultural production, including GMOs; only 37% (by weight) from renewably sourced material GMOs are used in fermentation of glucose to bio-PDO

feedstock is grown using methods of industrial agricultural production, including GMOs

the process has relatively high

energy and water requirements; emissions of pollutants to air and water during kraft process need to be addressed; potential toxicity issues of nanoparticles regarding incineration, composting, or recycling are unknown

hydroxide, volatile toxic, flammable, and malodorous emissions of sulfur; exposure to propionic, acetic, sulfuric, and nitric acids

exposure to pesticides, terephthalic acid, dimethyl terephthalate, and methanol; finely pulverized starch can cause powerful explosions

exposure to pesticides, alcohol or volatile solvents, alkaline and acid substances, and formaldehyde or glutaraldehyde

exposure to elevated temperature and pressure; exposure to disulfide, sodium hydroxide, isocyanates, volatile toxic, flammable, and malodorous emissions of sulfur, as well as to nanoparticles

Reprinted with permission from Ref. 35. # 2012, Elsevier. GMOs: genetically modified organisms; GHG: greenhouse gases.

4. Degradation of Plastics

Biodegradable plastics had a difficult start, as marketing claims exceeded performance. ‘‘The U.S. biodegradables industry fumbled at the beginning by intro- ducing starch filled (6–15%) polyolefins as true biodegradable materials. These at best were only biodisintegradable and not completely biodegradable. Data showed that only the surface starch biodegraded, leaving behind a recalcitrant polyethylene material.’’ (38). This situation questioned the entire biodegradable plastics industry, and has kept consumers and regulators confused for the under- standing of biodegradability and compostability. There are currently 23 active standards for testing the biodegradability or biobased content of plastics according to ASTM protocols (39). One has to discern between degradability in general and biodegradability in specific. Biodegradability is the capability of being degraded by biological activity (note that the in vitro activity of enzymes cannot be considered as biological activity). Degradation is the lowering of the molar masses of macromolecules that form the substances by chain scissions. All biodegradable


polymers are degradable polymers, but not necessarily vice versa (note that


Q1 Table 8. Environmental Impacts of Bioplastics

Production stage Environmental impacts feedstock new demand for biomass inputs can expand uses of

land, fossil fuels, chemical inputs, and water feedstock choices can reinforce existing problems

associated with corn and sugarcane; converting forests or glasslands to expand agricultural production can offset the CO2 sequestered by plants before harvest (Searchinger et al., 2008)

manufacturing and processing bioconversion is energy intensive (Gallezot, 2010) bioconversion may require the use of potentially

toxic petroleum-based solvents (Ahman and Dorgan, 2007) bioconversion produces significant water effluent needing treatment (Ahman and Dorgan, 2007)

bioconversion consumes water resources for fermentation, cooling, and heating

end-of-life fate compostable bioplastics may contaminate recycled plastic streams unless they are properly separated and managed (Song et al., 2009)

compostable plastics require high temperatures to decompose in a landfill and special industrial equipment to be composted (Song et al., 2009)

unless a landfill is managed well and kept dry, degrading bioplastics will release methane gas

life cycle assessments significant reductions of energy consumption and GHG emissions are possible (McKone et al., 20111; Akiyama et al., 2003); conversely, PHAs and PHBs have higher GHG emissions because of fossil fuel use for fertilizer production, agricultural production, corn wet milling, fermentation, polymer purification, and other production processes (Kurdikar et al., 2001)

Reprinted with permission from Ref. 24. # 2013, Elsevier.

Table 9. Comparison of a Bioplastic (PHB) with a Conventional Commodity Polymer (PP)

Impact category Unit PHB PP abiotic depletion kg Sbeq 21.8 41.4 global warming (GWP100) kg CO2eq 1960 3530 ozone layer depletion (ODP) kg CFC-11eq 0.00017 0.000862 human toxicity kg 1,4-DBeq 857 1870 fresh water aquatic ecotoxicity kg 1,4-DBeq 106 234 marine aquatic ecotoxicity kg 1,4-DBeq 1,290,000 1,850,000 terrestrial ecotoxicity kg 1,4-DBeq 8.98 44 photochemical oxidation kg C2H2 0.78 1.7 acidification kg SO2eq 24.9 48.8 eutrophication kg PO4

3-eq 5.19 5.84

Source: Ref. 36. LCIA of polymer production for 1000 kg of polymer product—CML 2 Baseline 2000


V2.03. Key: Underlined bold values are the lowest values in each category. Values in bold print are within 50% of the lowest value in each category.


!

compounds can contain nondegradable additives, and copolymers nondegradable moieties). Biomineralization is a process generally concomitant to biodegradation, biofragmentation, and bioerosion. Specific modes are ‘‘hydrodegradation’’ or hydrolysis (by the action of water), photodegradation (by visible or ultraviolet light), oxidative degradation (by the action of oxygen) or photooxidative degradation (by the combined action of light and oxygen), thermal degradation (by the action of heat), thermochemical degradation (by the combined effect of heat and chemical agents), and thermooxidative degradation (by the combined action of heat and oxygen). One can distinguish between physical and chemical degradation. Biodegradation is cell mediated (eg, bacteria). Enzymatic degradation is a result from the action of enzymes.

An environmentally degradable polymer is a polymer that can be degraded by the action of the environment, through, for example, air, light, heat, or microorganisms.

Depolymerization can be caused by the enzyme depolymerase. This term is to be used when monomers are recovered ( feedstock recycling).

Deterioration, which can stem from physical and/or chemical influences, is the deleterious alteration of a plastic material in quality.

Erosion is a degradation process that occurs at the surface and progresses from there into the bulk.

Fragmentation is the breakdown of a polymeric material into particles irrespective of the mechanism and the size of fragments.

Mineralization is the process through which an organic substance is converted into inorganic substances (CO2, H2O, and other inorganics).

Composting is the decomposition of organic wastes by fermentation. It can be performed industrially under aerobic or anaerobic conditions.

Biodegradable plastics must undergo degradation resulting from the action of naturally occurring microorganisms such as bacteria.

Compostable plastics must further meet the following two requirements:

• They must biodegrade at a rate comparable to common compostable organic materials.

• They must disintegrate fully and leave no large fragments or toxic residue.

In short, a biodegradable plastic cannot be called compostable if it breaks down too slowly, or if it leaves toxic residue or distinguishable fragments. In general, an increase in the hydrophobic character, the macromolecular weight, the crystallinity, or the size of spherulites decreases biodegradability (40). The higher the amount of natural polymers such as polysaccharides in blends, the faster the degradation progresses. Such blends are, however, not completely degraded; the bulk material will be rendered into minute particles of conventional polymer, which are no longer visible to the naked eye like litter, but are still present. An example is mulch film made from PE with starch as filler. Such materials are generally no longer used (41).

Ideally, plastics are mineralized, ie, broken down and converted to water and carbon dioxide after their use, which is mostly time limited. When a mineraliza-


tion product is CH4, which has a high greenhouse warming potential (31), the environmental impact is significantly aggravated.


Table 10. Biodegradable Polymers

Biodegradable polymers from renewable resources polylactide polyhydroxyalkanoates, eg, poly(3-

hydroxybutyrate) thermoplastic starch cellulose chitosan proteins

Biodegradable polymers from petroleum sources

aliphatic polyesters and copolyesters (eg, polybutylene succinate and poly(butylene succinate-co-adipate))

aromatic copolyesters (eg, poly(butylene adipate-co-terephthalate))

poly(3-caprolactone) polyesteramides polyvinyl alcohol

Source: Ref. 45. For details on compostability of plastics, see Ref. 45.

Degradation can occur by physical, chemical, and biological means. However, plastics were initially selected for their resistance to degradation in the environment (bioresistant polymers). They withstand attack by microorganisms. Their biostability is associated with the following problems:

• Littering (visible contamination). • Release of water-soluble and water-dispersed macromolecular compounds

and additives contained in the plastic products.

Some modes of degradation require that the plastic be exposed at the surface (UV light, O2), whereas other modes are only effective under special conditions of, eg, industrial composting systems. There are also additives for polymers intended to enhance their degradability (42,43).

For instance, BASF has been on the market for a decade with a compostable bioplastic made from fossil sources (Ecoflex) and one made from renewable sources (Ecovio). An overview of commercial compostable bioplastics is given, eg, in the UL database (44).

Table 10 lists several biodegradable polymers from renewable and petrochemical resources.

For details on compostability of plastics, see Reference 45. 5. History of Bioplastics

Natural plastic materials (chewing gum, shellac) have been used for thousands of years. In ancient times, natural plant gum was deployed to join pieces of wood in house building, and natural plant gum was applied as a waterproof coating to boats (46). Natural rubber came to the attention of Christopher Columbus in 1495, when he had landed on the island of Haiti and saw people playing with an elastic ball. Starch has been used for centuries as glue for paper and wood and as gum for


the textile industry (47).


The first plastics in the modern sense were produced in the end of 19th and beginning of 20th century. Celluloid and cellophane were the first ones, and they were biobased.

Natural rubber was originally derived from latex, a milky colloidal suspen- sion found in special trees. Its first use was cloth waterproofed with unvulcanized latex from Brazilian rubber trees.

In 1839, Charles Goodyear discovered vulcanization of natural rubber materials with sulfur for improving elasticity and durability. He also invented Ebonite (1852), a very hard rubber.

The first man-made plastic was Parkesine (1856), which was obtained from cellulose treated with nitric acid. Bakelite, the first fully synthetic thermoset, was invented in 1907. The material, polyoxybenzylmethylenglycolanhydride, is obtained in an elimination reaction of phenol with formaldehyde. Another early bioplastic, casein, was produced from milk proteins and lye. Casein, a family of related phosphoproteins, is still used today for paints, glues, and in cheesemaking. Galalith (invented around 1897) is a synthetic plastic material manufactured from casein and formaldehyde. Galalith was used for buttons around 1930.

In 1941, Henry Ford presented the ‘‘soybean car,’’ a plastic-bodied car shown at Dearborn Days, an annual community festival. It was 1000 lb lighter than a steel car; probably, the composition was ‘‘soybean fiber in a phenolic resin with formaldehyde used in the impregnation’’ (48).

Mass production of ‘‘conventional’’ petrochemical mass polymers such as PE, PP, PVC, PET, and PVC started around 1940–1950. Cheap crude oil has made possible the mass production of these petrochemical polymers, and bioplastics virtually disappeared (compare the case of fuels, where biobased fuels that were initially used for combustion were replaced by petrol and diesel).

Modern bioplastics started emerging in the 1980s, when people wanted to reduce the volume of waste in landfills. They hoped that degradable plastics discarded into landfills would take up less space once decomposed. This concept, however, failed, because landfills are sealed and oxygen, water, and sunlight are hardly available to break down the material.

Another concept that helped revive the interest in bioplastics was to reduce the use of petrochemicals for plastics production, as the price of crude oil became unstable and started to rise (see oil crises of the 1970s). The first biopolymers were blends of starch with conventional polymers, so that a certain biodegradability and use of natural feedstock were partly achieved.

Packaging, an area where plastic products have a short useful life, is currently one of the biggest markets for biopolymers, such as biodegradable plastic bags, compostable waste collection bags, and biodegradable or compostable food packaging.

Cheap oil and performance issues have retarded progress in biopolymers, despite growing customer concern about the environment.

In 2005, the chemical company Dow decided to pull out of bioplastics ‘‘due to slow sector maturation’’ after having invested an estimated $750 million (49). In 2012, bioplastics company Metabolix reduced its production capacity of PHA from 50,000 to 10,000 ton/yr (1), as sales volumes were too low at that time. Other


manufacturers have been successful in mass producing bioplastics, eg, Brazil’s Braskem (biobased PE made from sugarcane) or US NatureWorks (PLA).


6. Bioplastics by Genetic Engineering

Genetically modified organisms (GMOs) are extensively used in biotechnology. For instance, 80% of the >255 million tons of soybeans harvested annually are genetically modified (50). Genetically engineered plants (51) and bacteria (52) also show a good potential for bioplastics. Table 11 depicts several ‘‘phytofactories’’ for biopolymers.

Transgenic means that the organism has received an exogenous gene, a so- called transgene, so that it exhibits and transmits to its offspring new properties.

Apart from bacteria, also (transgenic) plants can be used to produce biopolymers such as PHA (53) (see Fig. 4).

7. Description of Important Bioplastics

At present, the biggest market share among biodegradable bioplastics is held by TPS and blends made thereof, accounting for approximately 60% of consumption (54). Next in line is PLA with approximately 20% market share, followed by CA with 15% market share. Other bioplastics such as PHAs are at a market share below 5%, at present. It is assumed that PLA is growing fastest (54).

Figure 5 shows an overview of biodegradable plastics in four families. An extensive list of bioplastics is provided in Reference 6.

Biobased polyethylene is the most common nondegradable biopolymer. Below, important biobased plastics are described. First, drop-in replacements (PE, PP, PVC, and PC) will be discussed, followed by biodegradable biopolymers. Note that also blends containing biobased plastics are manufactured. Drop-in bioplastics are chemically identical to their petrochemical counterparts, but they are at least partially derived from biomass. Generally, one can see a trend toward the replacement of conventional petroplastics by these drop-in solutions, with biodegradable bioplastics receiving comparatively less attention (55). Statistics from European Bioplastics show that durables accounted for almost 40% of bioplastics in 2011, up from around 12% in 2010 (19). This trend is in line with improving properties of bioplastic formulations.

7.1. Biobased PE. PE is one of the most widely used commodity thermoplastics, eg, for packaging (plastic bags, plastic films, geomembranes, and con- tainers including bottles). Variants are HDPE, LLDPE, and LDPE (high density PE, linear low density PE, and low density PE, respectively). The monomer, ethylene, is commonly made from crude oil (via cracking), natural gas, or shale gas (from NGLs (natural gas liquids) (56) or methane after dimerization (57)). Bio- based PE was first commercialized by Brazilian company Braskem utilizing local sugarcane-derived ethanol/ethylene as feedstock. In September 2010, Braskem started commercial production of biobased HDPE with a capacity of 200,000 ton/ yr. The material’s composition and performance are comparable to those of petroleum-based PE. According to ICIS (1), the ‘‘green PE’’ has a price premium of around 15–20%, which is possible in selected markets and covers the higher cost of production compared with petrochemical-based plastics. Another bio-PE plant


was built in Brazil by Dow Chemical and Mitsui. That plant has a capacity of 350,000 ton/yr with main target markets in flexible packaging, hygiene, and

Table 11. Novel Biopolymers Produced in Transgenic Plants

Polymer Native production host Structure Plant metabolite used for

Properties/applications synthesis PHAs bacteria; produced as a

carbon and energy storage polymer under nutrient limiting growth conditions (55)

• homopolymers and copolymers of polymerized hydroxy acids

• PHB most common target in plants

depends on polymer composition

• PHB: acetyl-CoA or acetoacetyl-CoA

• PHAMCL: fatty acids • PHBV: acetyl-CoA and

threonine

• depends on polymer composition

• applications in plastics, chemicals, and feed supplements

spider silk spiders; produced for webs and wrapping of prey

elastin mammals; extracellular matrix protein providing mechanical integrity to tissues

fibrous proteins with repetitive sequences possessing many nonpolar and hydrophobic amino acids

fibrous proteins with repetitive amino acid sequences

amino acids • multiple types of protein silk fibers exist that possess different properties (41,56)

• good elasticity and tensile strength

• clothing, textiles, medical uses

amino acids • tissue engineering, gels, fibers, scaffolds (57); soluble derivatives of elastin (ie, tropoelastin and elastin peptides(ELPs)) have more useful properties and thus broader applications (57)

• fusion of ELPs to other proteins can increase protein production (44)

collagen animals; protein found in connective tissue

fibrous proteins amino acids medical applications including tissue engineering, surgical implants, and drug delivery (58)

cyanophycin cyanobacteria and other photosynthetic and nonphotosynthetic bacteria; produced as

nitrogen stor

age

compound


nonribosomally produced amino acid polymer of aspartic acid backbone and arginine side groups

aspartic acid and arginine

• production of polyaspartate, a polymer with applications in superadsorbents, after chemical hydrolysis of arginine

• precursor for the production of chemicals (2)

Source: Ref. 53. PHB, poly[(R)-3-hydroxybutyrate]; PHAMCL, medium chain length PHA; PHBV, copolymer of (R)-3-hydroxybutyrate and (R)-3- hydroxyvalerate.

18


Fig. 4. Metabolic engineering of high yielding biomass and oilseed crops for the copro- duction of PHB and lignocellulosic biomass or seed oil. Large-scale production of PHB in plants has the potential to provide a renewable cheap source of polymeric material that can be used for the production of plastics, chemicals, and feed supplements with lignocellulosic or seed oil coproducts that can be used to produce energy. Transmission electron micro- graphs from thin sections of switchgrass leaf tissue and Camelina mature seeds are shown in the insets and illustrate the accumulation of PHB in the form of granules in a bundle sheath leaf chloroplast (switchgrass, top inset) and a seed plastid (Camelina, bottom inset), respectively. (Reprinted with permission from Reference 53. # 2015, Elsevier.)

Fig. 5. Different families of biodegradable polymers and their raw materials. (Source: Reference 41.)


medical applications. Since the project covers the entire value chain from growing sugarcane to producing the biopolymer (1), it is competitive to conventional polymer production.

7.2. Biobased PP. Polypropylene, the second most common commodity plastic, can likewise be made from renewably sourced feedstock. Propylene is accessible from methane via ethylene dimerization followed by metathesis (58). Braskem has announced plans to build a 30,000–50,000 ton/yr biobased PP production plant (1). A major market for biobased PP is the automotive industry, as approximately 50% of plastic in cars is PP. For details, see, eg, Reference 59.

7.3. Biobased PET. The third most common thermoplastic is PET. It is a thermoplastic polymer resin of the polyester family. It is mainly used for synthetic fibers (then called ‘‘polyester’’) and for packaging, primarily bottles. The monomer ethylene terephthalate (bis(2-hydroxyethyl) terephthalate) can be synthesized by esterification between terephthalic acid and ethylene glycol, or by transesterification between dimethyl terephthalate with ethylene glycol. Polymerization is done through a polycondensation reaction of the monomers, carried out immedi- ately after esterification/transesterification. Biobased PET can contain renewable monoethylene glycol (MEG), produced, eg, from sugarcane-derived ethylene, as being promoted by Coca Cola under the name Plantbottle (60,61). Its competitor Pepsi has announced a 100% renewable PET material (62). Scale-up to commercial production has been a hurdle so far (1) to replace conventional PET by a fully biobased alternative. Plantbottle PET is produced from terephthalic acid (70% by mass) and ethylene glycol (30% by mass), the latter coming from renewable ethanol. The formulation is also termed Bio-PET 30. An alternative to PET is the bioplastic polyethylene furanoate (PEF), which is expected to become commercially available as of 2016 (63). The bacteria Nocardia can degrade PET with its esterase enzyme (64).

7.4. Biobased PVC. PVC has been envisaged as one of the least environment-friendly synthetic polymers, setting free HCl and supporting dioxin forma- tion in combustion. On top, soft PVC contains plasticizers with special environmental challenges, eg, phthalates, so the material’s reputation is not so high. Company Solvay from Belgium has announced the production of 60,000 ton/ yr of biobased ethylene for the production of PVC (1). Also, efforts are underway to create biobased plasticizers for the replacement of phthalates. There are over 300 known plasticizers, with 50–100 being used commercially (65).

7.5. Biobased PC. Polycarbonates are situated between commodity plastics and engineering plastics, as they exhibit an interesting combination of temperature resistance, impact resistance, and optical properties. Conventional polycarbonate is made from toxic monomers, bisphenol A (BPA), and phosgene (COCl2).

An alternative polycarbonate can partly be made from isosorbide (derived from glucose: hydrogenation of glucose gives sorbitol, and isosorbide is obtained by double dehydration of sorbitol): Companies Mitsubishi and Roquette have announced pilot plants for making isosorbide and incorporating it into PC (66). Manufacturing PC from isosorbide and a diaryl carbonate removes the need to use phosgene and bisphenol A in the process (1). The biobased PC is seen as still far


from commercialization (1). In Reference 67, the potential of a derivative of cashew nutshell liquid (CNSL) as an alternative to BPA is discussed.


--

7.6. Biobased PU. Polyurethanes (PU, RPUR, and BUR) are thermo- setting polymers commonly formed by reacting a di- or polyisocyanate with a polyol. Applications are rigid foams. The polyols can be obtained from plant oil to make a biobased PU. Natural oil polyols (NOPs, biopolyols) (68) are derived from vegetable oils. Castor oil is suited best, as it consists mainly of ricinoleic acid, which has hydroxyl groups. Other vegetable oils such as canola oil, peanut oil, or soybean oil need to be treated to introduce OH groups, mainly by double bond oxidation.

7.7. Cellulose Acetate. Cellulose esters are another important group of bioplastics. The most common cellulose esters comprise CA, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB). They are thermoplastic materials produced through esterification of cellulose (45). Applications are synthetic fibers, cigarette filters, and formerly photography film.

7.8. Polylactic Acid. Polylactic acid or polylactate is obtained from the monomer lactic acid, which is produced from the microorganism-catalyzed fermentation of sugar or starch. It is similar in properties to PET and has FDA approval for food contact. Common raw materials are corn starch, sugarcane, and tapioca (starch extracted from cassava root). Chemically, PLA is not a polyacid (polyelectrolyte), but rather a polyester. Companies active in the field are, eg, NatureWorks, Purac, and Teijin (1). PLA is used for yogurt cups, where it replaces polystyrene. Due to inferior material properties (heat resistance, impact resistance, and low glass transition temperature), PLA is often blended with conventional petroplastics. Costs of PLA have improved over the last decade and are expected to go down further as capacity is added, eg, by NatureWorks (140,000 ton/yr) and Purac (750,000 ton/yr) (1). NatureWorks’ Ingeo is manufactured in a two-step process that starts with fermenting the dextrose derived from hydrolysis of corn starch. The product of the dextrose fermentation, lactic acid, is further treated to create the intermediary monomer lactide (the cyclic diester of lactic acid), which is then polymerized through opening polymerization (39).

Polylactic acid and its copolymers can also be obtained from engineered Escherichia coli (69).

Composite materials of PLA, eg, with woven bamboo fabric, have been reported (70).

PLA is subject to abiotic degradation (ie, simple hydrolysis of the ester bonds without requiring the presence of enzymes). It is also biocompatible.

Monomer stereochemistry (D- and L-lactic acid) can be controlled to impart targeted utility in the final polymers (71), by the relative contents of both homopolymers (D, L) and copolymers. Polymerization of a racemic mixture of L- and D-lactides usually yields poly-DL-lactide (PDLLA), which is amorphous.

Recycling of PLA, eg, to repolymerizable oligomer (72), is challenging. PLA has a strong potential for future use, spearheading bioplastics proliferation, since it is comparatively cheap and available on the market.

PLA contamination in PET recycling is a topic of concern. The biodegradation of a PLA cup over 2 months is shown in Figure 6.

Thermoreversible cross-linked PLA (TCP) for rewritable shape memory is


described in Reference 48. For details on PLA, see References 46 and [74]74–76 for applications.


Fig. 6. Biodegradation of a disposable cup made from PLA. Time sequence: 1, 15, and 30 days (top); 45 and 58 days (bottom). (Source: Reference 73.)

7.9. Polyhydroxyalkanoates. PHAs (77–82) are a wide group of biopolymers, but mostly refer to poly(3-hydroxybutyrate) and its copolymer PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)); see Figure 7 for the general structures.

These polyoxoesters are produced by bacteria from sugar or lipids through polyhydroxy fatty acids from anaerobic digestion. PHAs are an intracellular (energy storage) product of the bacteria (see Fig. 8).

Approximately 250 different bacteria were found to produce PHA. The bioplastics are then harvested through the destruction of the bacteria and are


Fig. 7. The general structure of polyhydroxyalkanoates. (Source: Reference 83.)


Fig. 8. Transmission electron microscope images: microbial cells containing native PHB granules (a), cells with damaged walls in acid pretreatment (b), PHB granules with attached residual cell mass (c), and purified PHB granules (d) (Source: Reference 84.)

separated from the microbial cell matter (centrifugation/filtration and PHA extraction using solvents such as chloroform).

PHAs have good barrier properties and, since they are biodegradable (85), are attractive for biomedical uses (1,39). PHA can also meet ASTM D7081, which is the standard specification for marine degradability (39).

The main attributes of PHAs are as follows:

• Fully biodegradable in soil, water, and compost. • Good printability. • Good resistance to grease and oils. • Can withstand boiling water (HDT >1200C).

Most commercial products are injection molding grades. PHAs are sold, eg, by company Metabolix. Issues that limit commercialization of PHA are their brittleness, a narrow processing window, a slow crystallization rate, and sensi- tivity to thermal degradation (1). Similar to PLA, material shortcomings can partly be overcome by blending with additives and other polymers. PHB is similar in properties to PP (see Table 12).

For a comparison of PHB and PP, see also Reference 36. The production rate of PHB-forming bacteria varies depending on substrates

and process conditions (see Table 13).


- -

Table 12. Physical Properties of Various PHAs and PP

P(HB-HN) Property PHB 3 mol% 14 mol% 25 mol% Polypropylene melting point, 0C 175 169 150 137 176 glass transition temperature (0C) 15 – – 1 10 crystalline, % 80 – – 40 70 Young’s modulus 3.5 2.9 1.5 0.7 1.7 tensile strength, MPa 40 38 35 30 34.5 elongation to break, % 6 – – – 400 impact strength, V/m 50 60 120 400 45

Source: Ref. 83.

Table 13. PHB Production by Bacillus sp. with Different Carbon Sources

Carbon source Dry cell weight, g/L PHB, g/L % PHB, w/w dextrose 12.58 5.02 39.90 xylose 13.408 5.02 37.44 sucrose 9.316 4.97 53.35 rhamnose 9.402 5.01 53.28 mannitol 9.942 5.00 50.29 maltose 8.636 4.88 56.51 lactose 8.502 5.06 59.52 mannose 9.114 4.97 54.53 galactose 15.494 4.92 31.75 starch 17.312 5.05 29.17 raffinose 8.37 5.07 60.57

Source: Ref. 86.

Agro and food wastes can also be used for PHA production, eg, rice husk, wheat bran, mango peel, potato peel, bagasse, and straw (87).

PHAs degrade fastest in anaerobic sewage and slowest in seawater. The degrading microbes colonize the polymer surface and secrete PHA depolymerases. Reactions are as follows:

PHA ! CO2 þ H2O ðaerobicallyÞ PHA ! CO2 þ H2O þ CH4 ðanaerobicallyÞ

Reactive extrusion can be used for grafting functional groups onto the PHA backbone by a solvent-free process.

For details on PHB, see References 88–96. 7.10. Polybutylene Succinate. Polybutylene succinate, sometimes

written as polytetramethylene succinate, is a thermoplastic, biodegradable aliphatic polyester with properties that are comparable to polypropylene. It is made from succinic acid and 1,4-butanediol (BDO). Companies active in the field are, eg, BioAmber, Reverdia, Myriant, and Purac (1).


7.11. Polyvinyl Alcohol. Polyvinyl alcohol (PVOH, PVA) is a biodegradable water-soluble polymer (97).


-- -- -- -- --

7.12. Biobased Polyethylene oxide. Polyethylene glycol (PEG) is a polyether compound with the formula H--(O--CH2--CH2)n--OH. It is soluble in

PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on molecular mass. All are oligomers of the monomer ethylene oxide. Generally, PEG is used for oligomers and polymers with a molecular mass below 20,000 g/mol and PEO for polymers with a molecular mass above 20,000 g/mol. The expression POE is used for a polymer of any molecular mass. PEG has numerous applications in industry and medicine.

7.13. Biobased Polyamide. Polyamides are macromolecules with repeating units linked by amide bonds. They occur naturally and artificially. Examples of the former are proteins, such as wool and silk. Synthetic polyamides are often used in textiles and the transportation industry. Two common PAs are the homopolymers PA 6 ([N--H--(CH2)5--CO]n made from e-caprolactam) and PA 66 ([NH (CH2)6 NH CO (CH2)4 CO]n made from hexamethylenediamine and adipic acid).

Rilsan is a commercially available biobased polyamide (PA 11) made from castor oil (sebacic acid).

7.14. Chitosan. Chitosan is a form of chitin, one of the most abundant organic material on Earth. Chitin is a tough polysaccharide found, eg, in the shells of shrimp and other crustaceans. The development of chitosan-based bioplastics is still in the beginning (98–100).

7.15. Thermoplastic Starch. Starch is the major carbohydrate energy storage product of plants. The group of polysaccharides is the most abundant biopolymer group on Earth. Starch is also cheap. It can even be sourced from wastes such as defatted cashew nut shells (101).

Concerning biopolymers, there are several options. First, starch can be converted into chemicals such as ethanol and organic acids, from which synthetic polymers can be made. Second, it can be used as filler in plastics. Third, modification of the starch, eg, by grafting, is possible.

The first attempts to use starch in bioplastics were made in the 1970s (41). Sorbitol and glycerol can be used to plasticize the starch into a plastic.

When blending starch with thermoplastic polymers (petro-derived or biobased), thermoplastic starch, which is biodegradable (biodisintegrable), is obtained. It was invented in 1988 (EP 0397819). One of the largest thermoplastic starch producers is Novamont with its product MaterBi, which has been on the market for two decades (39).

Apart from films, bags, and small appliances such as ballpoint pens and cutlery, expanded packages (foams) can be made from TPS, where properties are comparable to EPS and XPS foam (41) (see Fig. 9).

TPS is, eg, marketed as Plastarch Material (PSM) made from corn starch. For details on TPS, see References 41, 47, 103, and 104.

7.16. Cellophane. Cellophane is a thin, transparent sheet made of regenerated cellulose, a glucose polymer. The cellulose from, eg, wood, cotton, or hemp is dissolved in alkali and CS2 to produce viscose, from which a fiber (rayon) or a film (cellophane) can be made in a bath of sulfuric acid and sodium

water.


sulfate. It was invented around 1930 and amply used; however, due to the use of CS2 in manufacturing, its importance declined, although the material itself is


Fig. 9. Extruded starch foam. (Reprinted with permission from Reference 102. # 2015, Elsevier.)

biodegradable. Cellophane is used for food packaging and also to wrap cigars, as it allows them to ‘‘breathe’’ (the material is permeable to moisture). Note that the term ‘‘cellophane’’ has become genericized, so it is often used informally to refer plastic film products of other materials, too.

7.17. Polyesteramides. Polyesteramides (PEAs) are bioabsorbable. They can also be made from renewable resources. For details, see Reference 105.

7.18. Alginate. Alginate (alginic acid, algin) is a polysaccharide acquired from the cell walls of brown algae. Alginate has been exploited for a long time as a polyelectrolyte material (99). It can absorb 200–300 times its own weight in water. Alginates can be used for films and coatings (106), particularly of edible products.

7.19. Polycaprolactone. PCL is a biodegradable polyester. It has a very low melting point of around 600C. The most common use of polycaprolactone is in the manufacture of speciality polyurethanes. Biomedical applications include surgical suture.

Its physical properties make it a very tough, polyamide-like plastic that melts to a consistency like putty at only 600C. This makes PCL attractive for the hobbyist market and for rapid prototyping (softening can be achieved by immer- sion in hot water).

7.20. Polytrimethylene Terephthalate. Polytrimethylene terephthalate (PTT) is a new type of polyester. It has been applied to carpet and textile fibers, monofilaments, films, nonwoven fabrics, and in the engineering thermoplastics area (107). PTT is made from 1,3-propanediol (PDO), which can be obtained via several renewable routes, eg, by aerobic fermentation from glycerol or glucose. The bioprocess of PDO production was found to consume 40% less energy and to cut greenhouse gas emissions by 20% compared with petroleum-based propanediol (107). PTT is sold by DuPont as Sorona.

7.21. Polyglycolic Acid. Polyglycolic acid or polyglycolide is a bio-


degradable, thermoplastic polymer. It constitutes the simplest linear, aliphatic


polyester. The glycolic acid is derived from glucose, eg, from sugar beets, and glycolic acid is polymerized by polycondensation or ring-opening polymerization. PGA is a tough fiber-forming polymer. PGA and its copolymers, eg, (poly(lactic-co- glycolic acid) with lactic acid and poly(glycolide-co-caprolactone) with caprolactone, are used for the manufacture of absorbable sutures.

7.22. Poly(butylene adipate-co-terephthalate). Poly(butylene adipate-co-terephthalate) (PBAT) is a copolyester of adipic acid, 1,4-butanediol, and dimethyl terephthalate. It is marketed as biodegradable alternative to PE, eg, by BASF under the name Ecoflex and, blended with polylactic acid, as Ecovio.

7.23. Other Bioplastics. There are significantly more bioplastics under investigation or even available on the market, such as a lignin-based thermoplast (Arboform) (108) or gluten-based ones (9,109). They cannot be covered within the scope of this article. For soy protein plastic (SPP) and sugar beet pulp (SBP) plastics and composites, see Reference 110. For further bioplastics, see References 6, 111, and 112.

8. Biobased Additives

As mentioned earlier, plastics are composed of polymers and additives, which enhance performance. Additives can be organic or inorganic. Examples include mineral fillers, UV stabilizers, color pigments, flame retardants, processing aids, and plasticizers.

Several additives are problematic, eg, toxic compounds, heavy metals, and leaching/migrating additives. Conventionally produced organic additives can also be replaced by renewable ones.

Examples are as follows:

• Biobased lubricants. • Glucose esters as biobased PVC plasticizers (113). • Renewable air release additives (114). • Renewable dimethyl succinate (DMS) as solvent and as a raw material for

pigments and UV stabilizers (115).

Industry initiatives are reported in References 116 and 117. For more information on biobased additives, see, eg, Reference 118. Biobased

fibers (eg, hemp) and fillers (eg, rubberwood flour) for composite materials are out of the scope of this article.

9. Recycling of Bioplastics

The generic options for bioplastics disposal are shown in Figure 10.

Recycling can be achieved by physical, biological, and chemical means. Physical recycling can be considered an established technology.


Fig. 10. Options for disposal of bioplastics. (Source: Reference 6.)

The recycling industry has created a recycling code system from 1 to 7 for plastics. The higher the number, the more difficult it is to deploy the material profitably in useful post-consumer applications (see Fig. 11).

Figure 12 shows the four modes of biological treatment. Chemical treatment can encompass hydrolysis/solvolysis, hydrothermal

depolymerization, and enzymatic depolymerization. Thermal alternatives are incineration and pyrolysis. The former captures

the chemical energy, eg, for district heating from waste incineration plants, while the latter aims at recycling the monomers. A variant is dry-heat depolymerization.

Waste treatment of bioplastics has been an active field of research; see Figure 13 for the frequency of patent applications. Most of these patents are filed in Japan and the United States.

Fig. 11. Resin identification codes (RICs) for physical recycling. Bioplastics all fall under 7.


Fig. 12. The four types of biological waste treatment for biopolymers: aerobic and anaerobic. Abbreviations: PBAT, poly(butylene adipate-co-terephthalate); PCL, poly(e-caprolactone); PHA, polyhydroxyalkanoate; PLA, polylactide. (Source: Reference 6.)

Fig. 13. Patent applications on biopolymers and their waste treatment worldwide during the period January 1, 1990 through August 31, 2012. (Source: Reference 6.)

10. Labeling and Certification

Bioplastic products on the market today are found in many conventional applications alongside ‘‘standard’’ plastics, eg, bottles, cutlery, packaging goods


(bags), carpets, textiles, plates, and films. They are (partly) made from a variety of feedstocks including sugarcane, corn, rice, potatoes, cellulose, bagasse, and


Fig. 14. Competing terminology: ‘‘100% COMPOSTABLE BAG,’’ ‘‘100% COMPOSTABLE,’’ ‘‘100% BIODEGRADABLE,’’ and ‘‘BIODEGRADABLE PLASTIC.’’ (Source: Reference 39.)

others. Bioplastics are not readily distinguishable from regular plastics. Corpo- rations are making efforts to appear eco-friendly and green. Bioplastics (ie, biodegradable plastics and compostable plastics) have to be tested to validate claims (119).

Ambiguous and competing terminology is used in marketing; see Figure 14 as an example.

In the United States, the Federal Trade Commission controls environmental claims in the U.S. Code of Federal Regulations (CFR) Section 16, Part 260 (16 CFR 260)—Guides for the Use of Environmental Marketing Claims. Similar provisions exist in other countries.

Clear labeling and certification can help distinguish between conventional and biobased plastics. Labels to indicate a certain product quality are well established on the consumer market, eg, for organic food, energy efficiency, and fair trade.

Independent and internationally respected labels provide transparent and accurate information for customers, and they help maintain a good reputation of the bioplastics industry. Ideally, labels are linked to a recognized standard.

Currently, several (voluntary) certification systems exist worldwide with regard to compostability, eg, DIN CERTCO, VincS otte and European Bioplastics (Europe), BPI (USA), JBPA (Japan), and ABA (Australia). These systems are all based on the same international standards (EN 13432, ASTM D6400, and ISO


17088) with similar requirements, but nevertheless show some minor and some- Q2 times. In the United States, the percentage of biobased ingredients required for a


Fig. 15. Compostability logos used in different countries. (Source: References 122 and 123.)

product to be referred to as biobased is defined by the USDA (United States Department of Agriculture) on a product-by-product basis (120). ILSR (Institute for Local Self-Reliance) has recommended that a minimum of 50% biobased content for products to be considered biobased (120).

The organic carbon in a product can be assessed according to CEN/TS 16137 and ASTM D6866. Sometimes, biobased mass content is also used.

In the United States, the U.S. Composting Council worked with the Bio- degradable Products Institute (BPI) (121) to establish a labeling program to certify compostable products.

Certification can concern compostability and/or a renewable feedstock base. Commonly used logos for compostability are shown in Figure 15.

ASTM D6400 and EN 13432 demand ‘‘84 days disintegration; 180 days mineralization.’’ Additional requirements include limits for the content of heavy metals, ecotoxicity analysis, and the level of compost quality, which is determined by a plant growth test.

Strategies for the promotion of biodegradability and the suppression of biodegradability are discussed in Reference 6. The lifetime of bioplastics can be extended by cross-linking, blending, additivation, coatings, surface modification, and the removal of impurities. Ideally, the lifetime of bioplastics is tailored to the specific application.

11. Current Applications of Bioplastics

The use of bioplastics is as diverse as that of conventional plastics.

Below, several prominent applications of bioplastics are highlighted. For images, see, eg, Reference 122. Due to the ample usage options, this compilation cannot be complete.

Out of scope of this article are particularly biopolymers in controlled-release delivery systems (124) and tissue engineering. Lignosulfonates, humic acids, waxes, plant oils, xanthane, and proteins (eg, collagen, gelatin, keratin, wool,


and silk) are also not covered, as they are biopolymers of technical use, but not plastics.


Fig. 16. Markets for bioplastics (2012 data). (Source: Reference 8.)

Poultry feathers, which contain over 90% keratin, and of which >4 billion pounds are generated in the U.S. poultry industry each year alone, have been envisioned for bioplastics production (125), as fiber filler. As shown in Figure 16, the main applications for bioplastics are seen in packaging, the automotive industry, and agriculture.

11.1. Packaging. In the plastics industry today, there is no larger market segment than packaging, which consumes approximately 100 millions tons of materials per year. In Western Europe, 50% of all goods are packaged in plastics.

11.2. Mulching Film. The purpose of a mulching film, a polymer film, is to cover seeded areas in order to protect the growing plants from weeds and low temperatures, and to preserve humidity. Such films act as local greenhouses. Traditional mulching films made from black PE had to be collected and discarded. Biodegradable mulching films will decompose. They have environmental advantages of photodegradable polyethylene films that are only fragmented and not totally degradable.

11.3. Microbeads in Cosmetics. Plastic waste that ends up in the oceans is fragmented into small particles called ‘‘microplastics.’’ Fish and birds that take it for food eat these particles and inflict damage. Apart from containing and releasing toxic products, microplastics were found to act as concentrators for toxins (126) and persistent organic pollutants (POPs) (127). The microplastics become enriched in the food chain and end up on humans’ plates (126). Also, small polyester fibers from washing operations end in the environment. On top, several cosmetics such as facial scrubs, toothpastes, and shower gels deliberately contain microbeads of plastics. These microexfoliants serve the purpose of peeling. They


are too small to be filtered by sewage treatment plants. Biodegradable alternatives are, eg, alginate, chitosan, and gelatin microbeads (128).


11.4. Automotive Industry. The automotive industry is taking initiatives toward sustainability, including attempts to utilize bioplastics. Due to the large number of vehicles manufactured, the impact can be big. According to Renault, more than 500 different plastic parts are typically deployed in an average European car, eg, for bumper, fender, instrument panels, trims, headlamp, air intake manifold, fuel tanks, etc, and several plastics are used (PP, PA, HDPE, ABS, PC, POM, PBT, etc)

Examples of bioplastics in cars are as follows. Toyota claims to have been the first car manufacturer to use sugarcane-

based PET in vehicle liners and some interior surfaces. The company aims to have 20% of all plastic components in its vehicles made of bioplastics by 2015 (129). Fiat has used castor oil-derived polyamides and soybean-derived polyurethanes for car parts (129).

Seventy-five percent of Ford vehicles produced annually contain soybean- based foam in headrests (129)

Mazda Motors Corp. claims a plant-derived content above 80% in interior fittings in one model, plus a 100% plant-derived biofabric for seat covers (129).

For details, see Reference 130. 12. Challenges with Bioplastics

Brand owners seek solutions for a ‘‘green,’’ ‘‘eco-friendly’’ image, speaking about corporate social responsibility (CSR), and consumers are looking for sustainable— yet cost-effective—products. The development and widespread acceptance and proliferation of bioplastics have to face several challenges. Today, bioplastics can be considered to be in their infancy, yet there is significant potential. In the near term, blending with polyolefins and other petrobased plastics is a viable approach to start using them, contributing to sustainability, while concurrently working to improve performance and costs (17).

Bioplastics are commonly, without questioning, promoted as a ‘‘green’’ alternative to regular plastics; however, matters are more complex. A case-by- case life cycle assessment has to show whether their impact on the environment is really superior to that of conventional plastics. The following aspects have to be considered:

Composting: Often, bioplastics can only be composted in industrial, high

temperature composting facilities, which is generally positive; however, it limits the use of, eg, bioplastic bags for home composting, and bioplastic litter will still be visible.

Recycling: Bioplastics are generally not accepted for recycling with standard plastics, so mixed collections pose a problem. For instance, a small fraction of PHB in PET can render the recycled material useless for high value applications. Dedicated infrastructure for bioplastics collection will be necessary, which is not in place yet. While single use of neither petroplastics nor bioplastics is desired, concern over contamination of recycling streams is a


major barrier in bioplastics acceptance. For details on bioplastics recycling, see, eg, Reference 6 and the next section.


Fig. 17. Cost split for a mid-sized PLA plant. (Source: Reference 131.)

Performance: The density of bioplastics is generally higher than that of polyolefins (1.2–1.3 g/cm3 vs 0.9 g/cm3). Used in cars, bioplastics mean more weight, resulting in higher fuel consumption, for instance.

Costs: Generally, bioplastics are more expensive than petrobased plastics. Figure 17 shows the typical contribution to production costs for PLA manufacturing from raw materials (>3/4), investments, utilities, and labor.

Also for bioplastics, economies of scale apply, so pilot plants cannot compete with established, large petroplastics plants, and new commercial bioplastics plants are typically smaller than petrochemical ones.

Material and processing knowledge: Companies that manufacture plastic

goods from resins have less knowledge on the processing of bioplastics than with conventional plastics, so they are hesitating to switch, particularly since some bioplastics are more difficult to process (they require lower temperatures, or putting it another way, damage to the material is incurred more easily).

Sustainability of the feedstock: In case the feedstock is derived from food or grown of valuable cropland, food prices might increase due to competition. Land use change can have an adverse effect on climate change; see also the discussion about first-generation biofuels (aspects are large-scale monocrop- ping and the destruction of rainforests). Here, non-food feedstock, eg, cellulose or algae, could pose a solution. In case of lignocellulose (wood), two schemes that certify sustainability production are FSC and PEFC.

Other concerns: These include the lack of adequate labeling/certification (see also above), and, for instance, nanocomposites (20), which are used in some bioplastics (although they are deployed in conventional plastics, too). Some researchers investigate genetically modified organisms (plants and bacteria) for bioplastics production, eg, feedstock (glucose, ethanol) or plastics (PHB),


which also face acceptance concerns in the public.


Fig. 18. Market size for bioplastics. (a) Biobased vs biodegradable materials. (b) Split by material. (Source: Reference 8.)

13. Market Size of Bioplastics

Figure 18, showing data for 2012, estimates the global market size for bioplastics to amount to 1.4 million ton/yr, which is roughly 0.5% of the total current market for (new) plastics.

One-third of global bioplastics is manufactured in South America (2) (see Fig. 19). Figure 19 also shows a projection for bioplastics market size in 2017. One can see that the nonbiodegradable bioplastics will strongly increase, whereas biodegradable plastics will see only moderate growth (see also Section 14).


Fig. 19. Global bioplastics production (2012 data) by region (a) and type (b). (Source: European Bioplastics/University of Applied Sciences and Arts, Hanover (8).)


14. Market Outlook for Bioplastics

The growth in bioplastics is driven by the expansion in demand. One can observe a shift from compostable (biodegradable) to durable bioplastics, away from single-use applications such as disposable bags or plastic cutlery toward more valuable, high performance goods such as automotive parts and household appliances. This trend is coupled with an increase in biopolymer products’ performance (132).

The production capacity of 3.5 million tons in 2011—one-third of which was utilized—is expected to triple to nearly 12 million tons by 2020 (132). With an estimated total polymer production of roughly 400 million tons in 2020, the biobased share would then have increased from 1.5% in 2011 to 3% in 2020. The highest growth is expected in drop-in biopolymers. Biobased PET should reach a production capacity of about 5 million tons by the year 2020, using bioethanol from sugarcane, followed by biobased polyolefins such as PE and PP from the same feedstock. PLA and PHA are expected to at least quadruple the capacity between 2011 and 2020. Most investment in new biobased polymer capacities is estimated to happen in Asia and South America because of better access to feedstock. Europe’s share in bioplastics will decrease from 20 to 14% and North America’s share from 15 to 13%, whereas in Asia it will increase from 52 to 55% and in South America’s from 13 to 18%. This means that each region of the world will see an increase in bioplastics use (132).

15. Conclusions

The proliferation and use of bioplastics should not be determined by their relative costs, but by their performance instead. Specific advantages for target applications need to be worked out. Bioplastics are not generally more environmentally sound than conventional plastics. They can be based on renewable feedstock, biodegradable, or both. Bioplastics currently only constitute approximately 1% of global plastics production; however, a huge potential is seen. Drop-in bioplastics have identical properties to their petrochemical counterparts, which has acceler- ated their commercialization. ‘‘Green’’ PE and PET are already on the market, as are PLA and starch blends. With consumer consciousness and sustainability becoming new market drivers, the push to bring more bioplastics to commercialization has become stronger, improving properties and performance, and reducing production cost (1).

By finding suitable monomers from renewable feedstock, a cost-effective swap toward bioplastics is feasible, because no entirely new polymerization plant has to be built, but only the upstream infrastructure is amended, eg, by a fermentation unit or a catalytic cracker. The concept of a biorefinery (133) also fits well into bioplastics, several high value products can be obtained from a given feedstock/raw material mix, and integration brings costs down.


¼

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MAXIMILIAN LACKNER Vienna University of Technology, Vienna, Austria

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rv

Keywords/Abstract

Dear Author,

Keywords and abstracts will not be included in the print version of your article but only in the online version. The abstract and keywords are included in the print version only for your review.

Abstract:

Bioplastics are biobased polymers with two sustainability concepts: biodegradability and renewability. On the one hand, bioplastics that biodegrade to CO2 and H2O in the environment can be produced, eg, avoiding litter and damage to marine organisms. On the other hand, renewable feedstocks instead of petroleum can be used, for instance, corn, sugarcane, and algae, reducing dependence on crude oil and reducing the impact on the climate. Currently, bioplastics have a market share of 1%, yet they experience annual growth rates in excess of 20–30%. This article highlights some key aspects associated with bioplastics, the performance of which can be tailored to meet that of petrochemical polymers or to offer new properties, eg, by blending and additivation. Important bioplastics are TPS (thermoplastic starch), PLA (polylactic acid), PHAs (polyhydroxyalkanoates), and bio-PE, bio-PP, and bio-PET, which contain at least some renewable carbon.

Keywords: Bioplastics; biobased polymers; sustainability; biodegradability; compostability.

Author Query

1. Please include the references cited in Table 8 in the reference list or else delete them from the table body.

2. The intended meaning of the text ‘‘but nevertheless show some minor and sometimes’’ is not clear. Please check.

3. Please provide the name(s) of the assignee(s) in Reference 43.

BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE AND/OR ...BIOPLASTICS: BIOBASED PLASTICS AS RENEWABLE...

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