Bioplastics are
plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
materials produced from renewable
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
sources, such as
vegetable fats and oils
Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...
,
corn starch
Corn starch, maize starch, or cornflour (British English) is the starch derived from corn (maize) grain. The starch is obtained from the endosperm of the kernel. Corn starch is a common food ingredient, often used to thicken sauces or sou ...
,
straw
Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has a number ...
,
woodchips
Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste.
Woodchips may be used as a biomass solid fuel and are raw material ...
,
sawdust
Sawdust (or wood dust) is a by-product or waste product of woodworking operations such as sawing, sanding, milling, planing, and routing. It is composed of small chippings of wood. These operations can be performed by woodworking machinery, ...
, recycled
food waste
Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...
, etc. Some bioplastics are obtained by processing directly from
natural biopolymers including
polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
s (e.g.
starch
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
,
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
,
chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked Glucosamine, D-glucosamine (deacetylated unit) and N-Acetylglucosamine, ''N''-acetyl-D-glucosamine (acetylated unit). It is made by treating the chitin shell ...
and
alginate
Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. With metals such as sodium and calcium, its salts are known as alginates. Its colou ...
) and
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s (e.g.
soy protein
Soy protein is a protein that is isolated from soybean. It is made from soybean meal that has been dehulled and defatted. Dehulled and defatted soybeans are processed into three kinds of high protein commercial products: soy flour, concentrates, ...
,
gluten
Gluten is a structural protein naturally found in certain cereal grains. Although "gluten" often only refers to wheat proteins, in medical literature it refers to the combination of prolamin and glutelin proteins naturally occurring in all grain ...
and
gelatin
Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
), while others are chemically synthesised from
sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...
derivatives (e.g.
lactic acid
Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natu ...
) and
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
s (oils and fats) from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as
fossil-fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ma ...
plastics (also called petro-based polymers) are derived from
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
or
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
.
One advantage of bioplastics is their independence from
fossil fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...
as a raw material, which is a finite and globally unevenly distributed resource linked to
petroleum politics
Petroleum politics have been an increasingly important aspect of diplomacy since the rise of the petroleum industry in the Middle East in the early 20th century. As competition continues for a vital resource, the strategic calculations of major a ...
and
environmental impacts
Environmental issues are effects of human activity on the biophysical environment, most often of which are harmful effects that cause environmental degradation. Environmental protection is the practice of protecting the natural environment on t ...
.
Life cycle analysis
Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a commercial product, process, or service. For instance, in the case of ...
studies show that some bioplastics can be made with a lower
carbon footprint
A carbon footprint is the total greenhouse gas (GHG) emissions caused by an individual, event, organization, service, place or product, expressed as carbon dioxide equivalent (CO2e). Greenhouse gases, including the carbon-containing gases carbo ...
than their fossil counterparts, for example when
biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
is used as raw material and also for energy production. However, other bioplastics' processes are less efficient and result in a higher carbon footprint than fossil plastics.
The distinction between non-fossil-based (bio)plastic and fossil-based plastic is of limited relevance since materials such as petroleum are themselves merely ''fossilized'' biomass. As such, whether any kind of plastic is degradable or non-degradable (durable) depends on its molecular structure, not on whether or not the biomass constituting the raw material is fossilized. Both durable bioplastics, such as
Bio-PET
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, ...
or
biopolyethylene (bio-based analogs of fossil-based
polyethylene terephthalate
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...
and
polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
), and degradable bioplastics, such as
polylactic acid
Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula or , formally obtained by condensation of lactic acid with loss of water (hence its name). It can also be prepared by rin ...
,
polybutylene succinate, or
polyhydroxyalkanoates
Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids. When produced by bacteria they serve as both a source of energy and as a carbon store. More ...
, exist. Bioplastics must be recycled similar to fossil-based plastics to avoid plastic pollution; "drop-in" bioplastics (such as biopolyethylene) fit into existing recycling streams.
Biodegradability
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
may offer an end-of-life pathway in certain applications, such as agricultural mulch, but the concept of biodegradation is not as straightforward as many believe. Susceptibility to biodegradation is highly dependent on the chemical backbone structure of the polymer, and different bioplastics have different structures, thus it cannot be assumed that bioplastic in the environment will readily disintegrate. Conversely, biodegradable plastics can also be synthesized from fossil fuels.
As of 2018, bioplastics represented approximately 2% of the global plastics output (>380 million tons). With continued research on bioplastics, investment in bioplastic companies and rising scrutiny on fossil-based plastics, bioplastics are becoming more dominant in some markets, while the output of fossil plastics also steadily increases.
Proposed applications
Few commercial applications exist for bioplastics. Cost and performance remain problematic. Typical is the example of Italy, where biodegradable plastic bags are compulsory for shoppers since 2011 with the introduction of a specific law. Beyond structural materials, electroactive bioplastics are being developed that promise to
carry electric current.
Bioplastics are used for disposable items, such as
packaging
Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a co ...
, crockery, cutlery, pots, bowls, and straws.
File:BiodegradablePlasticUtensils1.jpg, Biodegradable plastic utensils
File:Bio-K Abfallbeutel Kompostbeutel CG.jpg, Plastics packaging made from bioplastics and other biodegradable
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
plastics
File:Flower Wrapping made of PLA-Blend Bio-Flex.jpg, Flower wrapping made of PLA-blend bio-flex
Biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
s are available as coatings for paper rather than the more common petrochemical coatings.
Bioplastics called drop-in bioplastics are chemically identical to their fossil-fuel counterparts but made from renewable resources. Examples include
bio-PE
Biopolyethylene (also known as renewable polyethylene) is polyethylene made out of ethanol, which becomes ethylene after a dehydration process. It can be made from various feedstocks including sugar cane, sugar beet, and wheat grain.
The fina ...
,
bio-PET
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, ...
,
bio-propylene,
bio-PP
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.
Polypropylene
belongs to the group of polyolefins and is ...
, and biobased nylons.
[Drop in bioplastics](_blank)
/ref> Drop-in bioplastics are easy to implement technically, as existing infrastructure can be used. A dedicated bio-based pathway allows to produce products that can not be obtained through traditional chemical reactions and can create products which have unique and superior properties, compared to fossil-based alternatives.
Types
Polysaccharide-based bioplastics
Starch-based plastics
Thermoplastic
A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.
Most thermoplastics have a high molecular weight. The polymer chains associate ...
starch represents the most widely used bioplastic, constituting about 50 percent of the bioplastics market. Simple starch bioplastic film can be made at home by gelatinizing starch and solution casting. Pure starch is able to absorb humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.
Humidity depe ...
, and is thus a suitable material for the production of drug capsules by the pharmaceutical sector. However, pure starch-based bioplastic is brittle. Plasticizer
A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture.
Plasticiz ...
such as glycerol
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
, glycol, and sorbitol
Sorbitol (), less commonly known as glucitol (), is a sugar alcohol with a sweet taste which the human body metabolizes slowly. It can be obtained by reduction of glucose, which changes the converted aldehyde group (−CHO) to a primary alcohol g ...
can also be added so that the starch can also be processed thermo-plastically. The characteristics of the resulting bioplastic (also called "thermoplastic starch") can be tailored to specific needs by adjusting the amounts of these additives. Conventional polymer processing techniques can be used to process starch into bioplastic, such as extrusion, injection molding, compression molding and solution casting. The properties of starch bioplastic is largely influenced by amylose
Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch, making up approximately 20–30%. Because of its tightly packed helical structure, amylose ...
/amylopectin Amylopectin is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Plants store starch within specialized organelles called amylopl ...
ratio. Generally, high-amylose starch results in superior mechanical properties. However, high-amylose starch has less processability because of its higher gelatinization temperature and higher melt viscosity.
Starch-based bioplastics are often blended with biodegradable polyesters to produce starch/polylactic acid, starch/polycaprolactone
Polycaprolactone (PCL) is a biodegradable polyester with a low melting point of around 60 °C and a glass transition temperature of about −60 °C. The most common use of polycaprolactone is in the production of speciality polyure ...
or starch/Ecoflex (polybutylene adipate-co-terephthalate produced by BASF) blends. These blends are used for industrial applications and are also compostable. Other producers, such as Roquette, have developed other starch/polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...
blends. These blends are not biodegradable, but have a lower carbon footprint than petroleum-based plastics used for the same applications.
Starch is cheap, abundant, and renewable.
Starch-based films (mostly used for packaging purposes) are made mainly from starch blended with thermoplastic polyesters to form biodegradable and compostable products. These films are seen specifically in consumer goods packaging of magazine wrappings and bubble films. In food packaging, these films are seen as bakery or fruit and vegetable bags. Composting bags with this films are used in selective collecting of organic waste. Further, starch-based films can be used as a paper.
Starch-based nanocomposites have been widely studied, showing improved mechanical properties, thermal stability, moisture resistance, and gas barrier properties.
Cellulose-based plastics
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...
bioplastics are mainly the cellulose esters (including cellulose acetate
In biochemistry, cellulose acetate refers to any acetate ester of cellulose, usually cellulose diacetate. It was first prepared in 1865. A bioplastic, cellulose acetate is used as a film base in photography, as a component in some coatings, and ...
and nitrocellulose
Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and ...
) and their derivatives, including celluloid
Celluloids are a class of materials produced by mixing nitrocellulose and camphor, often with added dyes and other agents. Once much more common for its use as photographic film before the advent of safer methods, celluloid's common contemporar ...
.
Cellulose can become thermoplastic when extensively modified. An example of this is cellulose acetate, which is expensive and therefore rarely used for packaging. However, cellulosic fibers added to starches can improve mechanical properties, permeability to gas, and water resistance due to being less hydrophilic than starch.
A group at Shanghai University was able to construct a novel green plastic based on cellulose through a method called hot pressing.
Other polysaccharide-based plastics
Other polysaccharides such as chitosan
Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked Glucosamine, D-glucosamine (deacetylated unit) and N-Acetylglucosamine, ''N''-acetyl-D-glucosamine (acetylated unit). It is made by treating the chitin shell ...
and alginate
Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. With metals such as sodium and calcium, its salts are known as alginates. Its colou ...
can also be processed into plastic forms. Chitosan is dissolvable in mild acidic conditions and thus can be easily processed into films by solution casting. Chitosan has an excellent film forming ability. Besides, chitosan, mixed with a limited amount of acid, can also be thermomechanically processed into a plasticised form using an internal batch mixer and compression molder. This high-viscosity condition during thermomechanical processing allows chitosan to be easily blended with plasticizers, nanoparticles, or other biopolymers. Under solution conditions, the production of blended materials based on chitosan, which is positively charged, with other negatively charged biopolymers such as carboxymethyl cellulose, alginate and proteins is challenging as the electrostatic interaction between the two biopolymers will usually lead to coacervates Coacervate ( or ) is an aqueous phase rich in macromolecules such as synthetic polymers, proteins or nucleic acids. It forms through liquid-liquid phase separation (LLPS), leading to a dense phase in thermodynamic equilibrium with a dilute phase. Th ...
. However, bulk chitosan blends can be produced by high-viscosity thermomechanical processing, which may also display much better mechanical properties and hydrolytic stability. Alginate (usually sodium alginate or calcium alginate) is dissolvable in water so alginate solutions can be cast into films. Blended with limited amounts of water and plasticizers, alginate can also be thermomechanically processed into plasticised films. Plasticisers typically as glycerol can make the processed chitosan or alginate films flexible.
Chitosan is a studied biopolymer that can be used as a packaging alternative that increases shelf life and reduces the use of synthetic plastics. Chitosan is a polysaccharide that is obtained through the deacetylation of chitin, the second most abundant polysaccharide on Earth derived from the non-edible portions of marine invertebrates
Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evo ...
. The increased use of chitosan has the possibility to reduce food waste and the waste from food packaging. Chitosan is compiled of antimicrobial activities and film forming properties which make it biodegradable and deter growth of spoilage. In comparison to degrading synthetic plastics, that may take years, biopolymers such as chitosan can degrade in weeks. Antimicrobial packaging includes techniques such as modified atmospheric packaging that reduce activities of microbes and bacterial growth. Chitosan as an alternative promotes less food waste and less reliance on non-degradable plastic materials.
Protein-based plastics
Bioplastics can be made from proteins from different sources. For example, wheat gluten and casein show promising properties as a raw material for different biodegradable polymers.
Additionally, soy protein is being considered as another source of bioplastic. Soy proteins have been used in plastic production for over one hundred years. For example, body panels of an original Ford automobile were made of soy-based plastic.
There are difficulties with using soy protein-based plastics due to their water sensitivity and relatively high cost. Therefore, producing blends of soy protein with some already-available biodegradable polyesters improves the water sensitivity and cost.
Some aliphatic polyesters
The aliphatic
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, or ...
biopolyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...
s are mainly polyhydroxyalkanoates (PHAs) like the poly-3-hydroxybutyrate
Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type ...
(PHB), polyhydroxyvalerate (PHV) and polyhydroxyhexanoate (PHH).
Polylactic acid (PLA)
Polylactic acid
Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula or , formally obtained by condensation of lactic acid with loss of water (hence its name). It can also be prepared by rin ...
(PLA) is a transparent plastic
Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptabi ...
produced from maize
Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
or dextrose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
. Superficially, it is similar to conventional petrochemical-based mass plastics like PS. Its advantages are that it is derived from plants and it biodegrades readily. Unfortunately, it exhibits inferior impact strength, thermal robustness, and barrier properties (blocking air transport across the membrane). PLA and PLA blends generally come in the form of granulates PLA is used on a limited scale for the production of films, fibers, plastic containers, cups, and bottles.
PLA is also the most common type of plastic filament used for home fused deposition modeling
Fused filament fabrication (FFF), also known as fused deposition modeling (with the trademarked acronym FDM), or called ''filament freeform fabrication'', is a 3D printing process that uses a continuous filament of a thermoplastic material. Filam ...
.
Poly-3-hydroxybutyrate
The biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
poly-3-hydroxybutyrate (PHB) is a polyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...
produced by certain bacteria processing glucose, corn starch or wastewater. Its characteristics are similar to those of the petroplastic polypropylene
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.
Polypropylene
belongs to the group of polyolefins and ...
. PHB production is increasing. The South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
n sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...
industry, for example, has decided to expand PHB production to an industrial scale. PHB is distinguished primarily by its physical characteristics. It can be processed into a transparent film with a melting point higher than 130 degrees Celsius, and is biodegradable without residue.
Polyhydroxyalkanoates
Polyhydroxyalkanoates
Polyhydroxyalkanoates or PHAs are polyesters produced in nature by numerous microorganisms, including through bacterial fermentation of sugars or lipids. When produced by bacteria they serve as both a source of energy and as a carbon store. More ...
(PHA) are linear polyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...
s produced in nature by bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
l fermentation
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
of sugar
Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...
or lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
s. 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 monomer
In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
Mo ...
s 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 is a biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
derived from natural oil. It is also known under the tradename Rilsan B, commercialized by Arkema
Arkema S.A. is a publicly listed, multi-national manufacturer of specialty materials, headquartered in Colombes, near Paris, France. It has three specialty materials segments (or divisions); adhesives, advanced materials and coatings. A furthe ...
. 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
Castor oil is a vegetable oil pressed from castor beans.
It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its density is 0.961 g/cm3. It includes a mixture of triglycerides in which about ...
, under the trade name EcoPaXX, commercialized by DSM.
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
The basic building block (monomer
In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
Mo ...
) of polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
is ethylene. Ethylene is chemically similar to, and can be derived from ethanol, which can be produced by fermentation of agricultural feedstocks such as sugar cane or corn. Bio-derived polyethylene is chemically and physically identical to traditional polyethylene – it does not biodegrade but can be recycled. The Brazilian chemicals group Braskem
Braskem is a Brazilian petrochemical company headquartered in São Paulo. The company is the largest petrochemical company in Latin America and has become a major player in the international petrochemical market (8th largest resin producer worldw ...
claims that using its method of producing polyethylene from sugar cane ethanol captures (removes from the environment) 2.15 tonnes of per tonne of Green Polyethylene produced.
Genetically modified feedstocks
With GM corn being a common feedstock, it is unsurprising that some bioplastics are made from this.
Under the bioplastics manufacturing technologies there is the "plant factory" model, which uses genetically modified crops
Genetically modified crops (GM crops) are plants used in agriculture, the DNA of which has been modified using genetic engineering methods. Plant genomes can be engineered by physical methods or by use of ''Agrobacterium'' for the delivery of ...
or genetically modified bacteria
Genetically modified bacteria were the first organisms to be modified in the laboratory, due to their simple genetics. These organisms are now used for several purposes, and are particularly important in producing large amounts of pure human prot ...
to optimise efficiency.
Polyhydroxyurethanes
The condensation of polyamines and cyclic carbonates produces polyhydroxyurethanes. Unlike traditional cross-linked polyurethanes, cross-linked polyhydroxyurethanes are in principle amenable to recycling and reprocessing through dynamic transcarbamoylation reactions.
Lipid derived polymers
A number bioplastic classes have been synthesized from plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
and animal derived fats and oils. Polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethan ...
s, polyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...
s, epoxy resins
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
and a number of other types of polymers have been developed with comparable properties to crude oil based materials. The recent development of olefin metathesis
Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds. Because of the relative simplicity of olefin metathesis, it often create ...
has opened a wide variety of feedstocks to economical conversion into biomonomers and polymers. With the growing production of traditional vegetable oils as well as low cost microalgae derived oils, there is huge potential for growth in this area.
Environmental impact
Materials such as starch, cellulose, wood, sugar and biomass are used as a substitute for fossil fuel resources to produce bioplastics; this makes the production of bioplastics a more sustainable activity compared to conventional plastic production.[Gironi, F., and Vincenzo Piemonte. “Bioplastics and Petroleum-Based Plastics: Strengths and Weaknesses.” Energy Sources, Part A: Recovery, Utilization and Environmental Effects, vol. 33, no. 21, 2011, pp. 1949–59, doi:10.1080/15567030903436830.] The environmental impact of bioplastics is often debated, as there are many different metrics for "greenness" (e.g., water use, energy use, deforestation, biodegradation, etc.). Hence bioplastic environmental impacts are categorized into nonrenewable energy use, climate change, eutrophication
Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...
and acidification
Acidification may refer to:
* Ocean acidification, decrease in the pH of the Earth's oceans
* Freshwater acidification, atmospheric depositions and soil leaching of SOx and NOx
* Soil acidification, buildup of hydrogen cations, which reduces the ...
.[Weiss, Martin, et al. “A Review of the Environmental Impacts of Biobased Materials.” Journal of Industrial Ecology, vol. 16, no. SUPPL.1, 2012, doi:10.1111/j.1530-9290.2012.00468.x.] Bioplastic production significantly reduces greenhouse gas emissions
Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and lar ...
and decreases non-renewable energy consumption. Firms worldwide would also be able to increase the environmental sustainability of their products by using bioplastics
Although bioplastics save more nonrenewable energy than conventional plastics and emit less green house gasses compared to conventional plastics, bioplastics also have negative environmental impacts such as eutrophication and acidification. Bioplastics induce higher eutrophication potentials than conventional plastics. Biomass production during industrial farming practices causes nitrate and phosphate to filtrate into water bodies; this causes eutrophication, the process in which a body of water gains excessive richness of nutrients. Eutrophication is a threat to water resources around the world since it causes harmful algal blooms that create oxygen dead zones, killing aquatic animals. Bioplastics also increase acidification. The high increase in eutrophication and acidification caused by bioplastics is also caused by using chemical fertilizer in the cultivation of renewable raw materials to produce bioplastics.
Other environmental impacts of bioplastics include exerting lower human and terrestrial ecotoxicity
Ecotoxicity, the subject of study in the field of ecotoxicology (a portmanteau of ecology and toxicology), refers to the biological, chemical or physical stressors that affect ecosystems. Such stressors could occur in the natural environment at ...
and carcinogenic potentials compared to conventional plastics. However, bioplastics exert higher aquatic ecotoxicity than conventional materials. Bioplastics and other bio-based materials increase stratospheric ozone
Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
depletion compared to conventional plastics; this is a result of nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a ...
emissions during fertilizer application during industrial farming for biomass production. Artificial fertilizers increase nitrous oxide emissions especially when the crop does not need all the nitrogen. Minor environmental impacts of bioplastics include toxicity through using pesticides on the crops used to make bioplastics. Bioplastics also cause carbon dioxide emissions from harvesting vehicles. Other minor environmental impacts include high water consumption for biomass cultivation, soil erosion, soil carbon losses and loss of biodiversity
Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...
, and they are mainly are a result of land use associated with bioplastics. Land use for bioplastics production leads to lost carbon sequestration
Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land ...
and increases the carbon costs while diverting land from its existing uses
Although bioplastics are extremely advantageous because they reduce non-renewable consumption and GHG emissions, they also negatively affect the environment through land and water consumption, using pesticide and fertilizer, eutrophication and acidification; hence one's preference for either bioplastics or conventional plastics depends on what one considers the most important environmental impact.
Another issue with bioplastics, is that some bioplastics are made from the edible parts of crops.
This makes the bioplastics compete with food production because the crops that produce bioplastics can also be used to feed people. These bioplastics are called "1st generation feedstock bioplastics".
2nd generation feedstock bioplastics use non-food crops (cellulosic feedstock) or waste materials from 1st generation feedstock (e.g. waste vegetable oil). Third generation feedstock bioplastics use algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
as the feedstock.
Biodegradation of Bioplastics
Biodegradation of any plastic is a process that happens at solid/liquid interface whereby the enzymes in the liquid phase depolymerize the solid phase. Certain types of bioplastics as well as conventional plastics containing additives are able to biodegrade. Bioplastics are able to biodegrade in different environments hence they are more acceptable than conventional plastics.[Emadian, S. Mehdi, et al. “Biodegradation of Bioplastics in Natural Environments.” Waste Management, vol. 59, Elsevier Ltd, 2017, pp. 526–36, doi:10.1016/j.wasman.2016.10.006.] Biodegradability
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
of bioplastics occurs under various environmental conditions including soil, aquatic environments and compost. Both the structure and composition of biopolymer or bio-composite have an effect on the biodegradation process, hence changing the composition and structure might increase biodegradability. Soil and compost as environment conditions are more efficient in biodegradation due to their high microbial diversity. Composting not only biodegrades bioplastics efficiently but it also significantly reduces the emission of greenhouse gases. Biodegradability of bioplastics in compost environments can be upgraded by adding more soluble sugar and increasing temperature. Soil environments on the other hand have high diversity of microorganisms making it easier for biodegradation of bioplastics to occur. However, bioplastics in soil environments need higher temperatures and a longer time to biodegrade. Some bioplastics biodegrade more efficiently in water bodies and marine systems; however, this causes danger to marine ecosystems and freshwater. Hence it is accurate to conclude that biodegradation of bioplastics in water bodies which leads to the death of aquatic organisms and unhealthy water can be noted as one of the negative environmental impacts of bioplastics.
Industry and markets
While plastics based on organic materials were manufactured by chemical companies throughout the 20th century, the first company solely focused on bioplastics—Marlborough Biopolymers—was founded in 1983. However, Marlborough and other ventures that followed failed to find commercial success, with the first such company to secure long-term financial success being the Italian company Novamont, founded in 1989.
Bioplastics remain less than one percent of all plastics manufactured worldwide. Most bioplastics do not yet save more carbon emissions than are required to manufacture them. It is estimated that replacing 250 million tons of the plastic manufactured each year with bio-based plastics would require 100 million hectares of land, or 7 percent of the arable land on Earth. And when bioplastics reach the end of their life cycle, those designed to be compostable and marketed as biodegradable are often sent to landfills due to the lack of proper composting facilities or waste sorting, where they then release methane as they break down anaerobically.
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:
History and development of bioplastics
* 1925: Polyhydroxybutyrate
Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. The poly-3-hydroxybutyrate (P3HB) form of PHB is probably the most common type ...
was isolated and characterised by French microbiologist Maurice Lemoigne Maurice may refer to:
People
*Saint Maurice (died 287), Roman legionary and Christian martyr
*Maurice (emperor) or Flavius Mauricius Tiberius Augustus (539–602), Byzantine emperor
*Maurice (bishop of London) (died 1107), Lord Chancellor and Lo ...
* 1855: First (inferior) version of linoleum
Linoleum, sometimes shortened to lino, is a floor covering made from materials such as solidified linseed oil (linoxyn), Pine Resin, pine resin, ground Cork (material), cork dust, sawdust, and mineral fillers such as calcium carbonate, most com ...
produced
* 1862: At the Great London Exhibition, Alexander Parkes
Alexander Parkes (29 December 1813 29 June 1890) was a metallurgist and inventor from Birmingham, England. He created Parkesine, the first man-made plastic.
Biography
The son of a manufacturer of brass locks, Parkes was apprenticed to Messenger ...
displays Parkesine
Celluloids are a class of materials produced by mixing nitrocellulose and camphor, often with added dyes and other agents. Once much more common for its use as photographic film before the advent of safer methods, celluloid's common contemporar ...
, the first thermoplastic. Parkesine is made from nitrocellulose and had very good properties, but exhibits extreme flammability. (White 1998)
* 1897: Still produced today, Galalith is a milk-based bioplastic that was created by German chemists in 1897. Galalith is primarily found in buttons. (Thielen 2014)
* 1907: Leo Baekeland invented Bakelite
Polyoxybenzylmethylenglycolanhydride, better known as Bakelite ( ), is a thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde. The first plastic made from synthetic components, it was developed ...
, which received the National Historic Chemical Landmark for its non-conductivity and heat-resistant properties. It is used in radio and telephone casings, kitchenware, firearms and many more products. (Pathak, Sneha, Mathew 2014)
* 1912: Brandenberger invents Cellophane
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated w ...
out of wood, cotton, or hemp cellulose. (Thielen 2014)
* 1920s: Wallace Carothers finds Polylactic Acid (PLA) plastic. PLA is incredibly expensive to produce and is not mass-produced until 1989. (Whiteclouds 2018)
* 1926: Maurice Lemoigne invents polyhydroxybutyrate (PHB) which is the first bioplastic made from bacteria. (Thielen 2014)
* 1930s: The first bioplastic car was made from soy beans by Henry Ford. (Thielen 2014)
* 1940-1945: During World War II, an increase in plastic production is seen as it is used in many wartime materials. Due to government funding and oversight the United States production of plastics (in general, not just bioplastics) tripled during 1940-1945 (Rogers 2005). The 1942 U.S. government short film '' The Tree in a Test Tube'' illustrates the major role bioplastics played in the World War II victory effort and the American economy of the time.
* 1950s: Amylomaize (>50% amylose content corn) was successfully bred and commercial bioplastics applications started to be explored. (Liu, Moult, Long, 2009) A decline in bioplastic development is seen due to the cheap oil prices, however the development of synthetic plastics continues.
* 1970s: The environmental movement spurred more development in bioplastics. (Rogers 2005)
* 1983: The first bioplastics company, Marlborough Biopolymers, is started which uses a bacteria-based bioplastic called biopal. (Feder 1985)
* 1989: The further development of PLA is made by Dr. Patrick R. Gruber when he figures out how to create PLA from corn. (Whiteclouds 2018). The leading bioplastic company is created called Novamount. Novamount uses matter-bi, a bioplastic, in multiple different applications. (Novamount 2018)
* 1992: It is reported in Science that PHB can be produced by the plant Arabidopsis thaliana. (Poirier, Dennis, Klomparens, Nawrath, Somerville 1992)
* Late 1990s: The development of TP starch and BIOPLAST from research and production of the company BIOTEC lead to the BIOFLEX film. BIOFLEX film can be classified as blown film extrusion, flat film extrusion, and injection moulding lines. These three classifications have applications as follows: Blown films - sacks, bags, trash bags, mulch foils, hygiene products, diaper films, air bubble films, protective clothing, gloves, double rib bags, labels, barrier ribbons; Flat films - trays, flower pots, freezer products and packaging, cups, pharmaceutical packaging; Injection moulding - disposable cutlery, cans, containers, performed pieces, CD trays, cemetery articles, golf tees, toys, writing materials. (Lorcks 1998)
* 2001: Metabolix inc. purchases Monsanto's biopol business (originally Zeneca) which uses plants to produce bioplastics. (Barber and Fisher 2001)
* 2001: Nick Tucker uses elephant grass as a bioplastic base to make plastic car parts. (Tucker 2001)
* 2005: Cargill and Dow Chemicals is rebranded as NatureWorks and becomes the leading PLA producer. (Pennisi 2016)
* 2007: Metabolix inc. market tests its first 100% biodegradable plastic called Mirel, made from corn sugar fermentation and genetically engineered bacteria. (Digregorio 2009)
* 2012: A bioplastic is developed from seaweed proving to be one of the most environmentally friendly bioplastics based on research published in the journal of pharmacy research. (Rajendran, Puppala, Sneha, Angeeleena, Rajam 2012)
* 2013: A patent is put on bioplastic derived from blood and a crosslinking agent like sugars, proteins, etc. (iridoid derivatives, diimidates, diones, carbodiimides, acrylamides, dimethylsuberimidates, aldehydes, Factor XIII, dihomo bifunctional NHS esters, carbonyldiimide, glyoxyls, proanthocyanidin, reuterin). This invention can be applied by using the bioplastic as tissue, cartilage, tendons, ligaments, bones, and being used in stem cell delivery. (Campbell, Burgess, Weiss, Smith 2013)
* 2014: It is found in a study published in 2014 that bioplastics can be made from blending vegetable waste (parsley and spinach stems, the husks from cocoa, the hulls of rice, etc.) with TFA solutions of pure cellulose creates a bioplastic. (Bayer, Guzman-Puyol, Heredia-Guerrero, Ceseracciu, Pignatelli, Ruffilli, Cingolani, and Athanassiou 2014)
* 2016: An experiment finds that a car bumper that passes regulation can be made from nano-cellulose based bioplastic biomaterials using banana peels. (Hossain, Ibrahim, Aleissa 2016)
* 2017: A new proposal for bioplastics made from Lignocellulosics resources (dry plant matter). (Brodin, Malin, Vallejos, Opedal, Area, Chinga-Carrasco 2017)
* 2018: Many developments occur including Ikea starting industrial production of bioplastics furniture (Barret 2018), Project Effective focusing on replacing nylon with bio-nylon (Barret 2018), and the first packaging made from fruit (Barret 2018).
*2019: Five different types of Chitin nanomaterials were extracted and synthesized by the 'Korea Research Institute of Chemical Technology' to verify strong personality and antibacterial effects. When buried underground, 100% biodegradation was possible within six months.
*This is not a comprehensive list. These inventions show the versatility of bioplastics and important breakthroughs. New applications and bioplastics inventions continue to occur.
Testing procedures
Industrial compostability – EN 13432, ASTM D6400
The EN 13432 industrial standard must be met in order to claim that a plastic product is compostable in the European marketplace. In summary, it requires multiple tests and sets pass/fail criteria, including disintegration (physical and visual break down) of the finished item within 12 weeks, biodegradation (conversion of organic carbon into ) of polymeric ingredients within 180 days, plant toxicity and heavy metals. The ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
6400 standard is the regulatory framework for the United States and has similar requirements.
Many starch
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
-based plastics, PLA-based plastics and certain aliphatic
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, or ...
-aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
co-polyester
Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...
compounds, such as succinates and adipates
Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annually, ...
, have obtained these certificates. Additive-based bioplastics sold as photodegradable or Oxo Biodegradable do not comply with these standards in their current form.
Compostability – ASTM D6002
The ASTM D 6002 method for determining the compostability of a plastic defined the word ''compost
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...
able'' as follows:
that which is capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds and biomass at a rate consistent with known compostable materials.
This definition drew much criticism because, contrary to the way the word is traditionally defined, it completely divorces the process of "composting" from the necessity of it leading to humus
In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...
/compost as the end product. The only criterion this standard ''does'' describe is that a compostable plastic must look to be going away as fast as something else one has already established to be compostable under the ''traditional'' definition.
Withdrawal of ASTM D 6002
In January 2011, the ASTM withdrew standard ASTM D 6002, which had provided plastic manufacturers with the legal credibility to label a plastic as compostable
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...
. Its description is as follows:
This guide covered suggested criteria, procedures, and a general approach to establish the compostability of environmentally degradable plastics.
The ASTM has yet to replace this standard.
Biobased – ASTM D6866
The ASTM D6866 method has been developed to certify the biologically derived content of bioplastics. Cosmic rays colliding with the atmosphere mean that some of the carbon is the radioactive isotope carbon-14
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...
. CO2 from the atmosphere is used by plants in photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
, so new plant material will contain both carbon-14 and carbon-12
Carbon-12 (12C) is the most abundant of the two stable isotopes of carbon (carbon-13 being the other), amounting to 98.93% of element carbon on Earth; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-12 i ...
. Under the right conditions, and over geological timescales, the remains of living organisms can be transformed into fossil fuels
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. 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
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
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
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...
.
There is an important difference between biodegradability
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
and biobased content. A bioplastic such as high-density polyethylene (HDPE) 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
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
– ASTM D5511-02 and ASTM D5526
The ASTM D5511-12 and ASTM D5526-12 are testing methods that comply with international standards such as the ISO DIS 15985 for the biodegradability
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
of plastic.
See also
* Alkane
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...
* Biofuel
Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...
* Biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
* BioSphere Plastic
BioSphere Plastic is a manufacturer of biodegradable additives. The company states that their product enhances the biodegradation of synthetic polymers by addition of their technology. It has a capacity at or around 5,800 metric tons a year and ha ...
* Organisms breaking down plastic
* Celluloid
Celluloids are a class of materials produced by mixing nitrocellulose and camphor, often with added dyes and other agents. Once much more common for its use as photographic film before the advent of safer methods, celluloid's common contemporar ...
* Edible tableware
Edible tableware is tableware, such as plates, drinkware glasses, utensils and cutlery, that is edible. Edible tableware can be homemade and has also been mass-produced by some companies, and can be prepared using many various foods.
Overview
...
* Food vs. fuel
Food versus fuel is the dilemma regarding the risk of diverting farmland or crops for biofuels production to the detriment of the food supply. The biofuel and food price debate involves wide-ranging views, and is a long-standing, controversial ...
* Galalith
Galalith (Erinoid in the United Kingdom) is a synthetic plastic material manufactured by the interaction of casein and formaldehyde. The commercial name is derived from the Ancient Greek words (, "milk") and (, "stone"). It is odourless, inso ...
* Health concerns of certain non-biodegradable (fossil fuel-based) plastic food packaging
* Organic photovoltaics
An organic solar cell (OSC) or plastic solar cell is a type of photovoltaic that uses organic electronics, a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport t ...
* Sustainable packaging
References
Further reading
Plastics Without Petroleum History and Politics of 'Green' Plastics in the United States
''Plastics and the environment''
"The Social construction of Bakelite: Toward a theory of invention"
in ''The Social Construction of Technological Systems'', pp. 155–182
External links
Assessment of China's Market for Biodegradable Plastics
May 2017, GCiS China Strategic Research
{{Packaging
Biodegradable waste management
Polymer chemistry