Biodegradable bags are bags that are capable of being decomposed by bacteria or other living organisms. [1]
Each year approximately 500 billion to 1 trillion plastic bags are used worldwide. [2]
In typical parlance, the word biodegradable is distinct in meaning from compostable. While biodegradable simply means an object is capable of being decomposed by bacteria or other living organisms, "compostable" in the plastic industry is defined as able to decompose in aerobic environments that are maintained under specific controlled temperature and humidity conditions. Compostable means 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. (ref: ASTM International D 6002)
The inclusion of "inorganic materials" precludes the end product from being considered as compost, or humus, which is purely organic material[ opinion ]. Indeed, under the ASTM definition, the only criterion needed for a plastic to be called compostable is that it has to appear to go away at the same rate as something else that one already knows is compostable under the traditional definition[ citation needed ].
Plastic bags can be made "oxo-biodegradable" by being manufactured from a normal plastic polymer (i.e. polyethylene) or polypropylene incorporating an additive which causes degradation and then biodegradation of the polymer (polyethylene) due to oxidation.
The trade association for the oxo-biodegradable plastics industry is the Oxo-biodegradable Plastics Association, which will certify products tested according to ASTM D6954 or (starting 1 January 2010) UAE 5009:2009
The trade associations for the compostable plastics industry are the Biodegradable Products Institute, "European Bioplastics", and SPIBioplastics Council. Money is certified as compostable for industrial composting conditions in the United States if they comply with ASTM D6400, and in Europe with the EN13432.
Most bags that are manufactured from plastic are made from corn-based materials, like polylactic acid blends. Biodegradable plastic bags are nowadays as strong and reliable as traditional (mostly polyethylene)-bags. Many bags are also made from paper, organic materials like Manila hemp, or polycaprolactone. [2] [3] [4]
"The public looks at biodegradable as something magical," even though the term is broadly used, according to Ramani Narayan, a chemical engineer at Michigan State University in East Lansing, and science consultant to the Biodegradable Plastics Institute. "This is the most used and abused and misused word in our dictionary right now. In the Great Pacific garbage patch, biodegradable plastics break up into small pieces that can more easily enter the food chain by being consumed." [5]
In-plant scrap can often be recycled but post-consumer sorting and recycling is difficult. Bio-based polymers will contaminate the recycling of other more common polymers. While oxo-biodegradable plastic manufacturers claim that their bags are recyclable, many plastic film recyclers will not accept them, as there have been no long-term studies on the viability of recycled-content products with these additives. Further, the Biodegradable Plastics Institute (BPI) says that the formulation of additives in oxo films varies greatly, which introduces even more variability in the recycling process. [6] SPI Resin identification code 7 is applicable.
Since many of these plastics require access to sunlight, oxygen, or lengthy periods of time to achieve degradation or biodegradation, the U.S. Federal Trade Commission's Guides for the Use of Environmental Marketing Claims, commonly called the "green guide", [7] require proper marking of these products to show their performance limits.
The Federal Trade Commission provides an example:
Example 1: A trash bag is marketed as "degradable," with no qualification or other disclosure. The marketer relies on soil burial tests to show that the product will decompose in the presence of water and oxygen. The trash bags are customarily disposed of in incineration facilities or at sanitary landfills that are managed in a way that inhibits degradation by minimizing moisture and oxygen. Degradation will be irrelevant for those trash bags that are incinerated and, for those disposed of in landfills, the marketer does not possess adequate substantiation that the bags will degrade in a reasonably short period of time in a landfill. The claim is therefore deceptive.
Since there are no pass-fail tests for "biodegradable" plastic bags, manufacturers must print on the product the environmental requirements for biodegradation to take place, time frame and end results in order to be within US Trade Requirements.
In 2007, the State of California essentially made the term "biodegradable bags" illegal, [8] unless such terms are "substantiated by competent and reliable evidence to prevent deceiving or misleading consumers about environmental impact of degradable, compostable, and biodegradable plastic bags, food service ware, and packaging."
In 2010, an Australian manufacturer of plastic bags who made unsubstantiated or unqualified claims about biodegradability was fined by the Australian Competition & Consumer Commission, which is the Australian equivalent of the U.S. Federal Trade Commission. [9]
In recent years, the Biodegradable Products Institute and related companies have claimed products compost in available compost facilities at 60 °C (140 °F). The Vermont attorney general found these claims to be misleading and sued compostable plastic companies for false claims. [10]
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 biodegradation occurs under a specific set of circumstances.
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition. Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. The rate of this degradation varies significantly; biodegradation can take decades, whereas some industrial processes can completely decompose a polymer in hours.
Plastic shopping bags, carrier bags, or plastic grocery bags are a type of plastic bag used as shopping bags and made from various kinds of plastic. In use by consumers worldwide since the 1960s, these bags are sometimes called single-use bags, referring to carrying items from a store to a home. However, it is rare for bags to be worn out after single use and in the past some retailers incentivised customers to reuse 'single use' bags by offering loyalty points to those doing so. Even after they are no longer used for shopping, reuse for storage or trash is common, and modern plastic shopping bags are increasingly recyclable or compostable. In recent decades, numerous countries have introduced legislation restricting the provision of plastic bags, in a bid to reduce littering and plastic pollution.
A plastic bag, poly bag, or pouch is a type of container made of thin, flexible, plastic film, nonwoven fabric, or plastic textile. Plastic bags are used for containing and transporting goods such as foods, produce, powders, ice, magazines, chemicals, and waste. It is a common form of packaging.
A bin bag, rubbish bag, garbage bag, bin liner, trash bag or refuse sack is a disposable bag used to contain solid waste. Such bags are useful to line the insides of waste containers to prevent the insides of the receptacle from becoming coated in waste material. Most bags today are made out of plastic, and are typically black, white, or green in color.
Plastic recycling is the processing of plastic waste into other products. Recycling can reduce dependence on landfill, conserve resources and protect the environment from plastic pollution and greenhouse gas emissions. Recycling rates lag those of other recoverable materials, such as aluminium, glass and paper. Through 2015, the world produced some 6.3 billion tonnes of plastic waste, only 9% of which has been recycled, and only ~1% has been recycled more than once. Additionally, 12% was incinerated and the remaining 79% sent to landfill or to the environment including the ocean.
Polylactic acid, also known as poly(lactic acid) or polylactide (PLA), is a thermoplastic polyester with backbone formula (C
3H
4O
2)
n or [–C(CH
3)HC(=O)O–]
n, formally obtained by condensation of lactic acid C(CH
3)(OH)HCOOH with loss of water. It can also be prepared by ring-opening polymerization of lactide [–C(CH
3)HC(=O)O–]
2, the cyclic dimer of the basic repeating unit.
Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc. Some bioplastics are obtained by processing directly from natural biopolymers including polysaccharides and proteins, while others are chemically synthesised from sugar derivatives and lipids from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as fossil-fuel plastics are derived from petroleum or natural gas.
Polyethylene or polythene film biodegrades naturally, albeit over a long period of time. Methods are available to make it more degradable under certain conditions of sunlight, moisture, oxygen, and composting and enhancement of biodegradation by reducing the hydrophobic polymer and increasing hydrophilic properties.
Biodegradable plastics are plastics that can be decomposed by the action of living organisms, usually microbes, into water, carbon dioxide, and biomass. Biodegradable plastics are commonly produced with renewable raw materials, micro-organisms, petrochemicals, or combinations of all three.
PBAT is a biodegradable random copolymer, specifically a copolyester of adipic acid, 1,4-butanediol and terephthalic acid. PBAT is produced by many different manufacturers and may be known by the brand names ecoflex, Wango,Ecoworld, Eastar Bio, and Origo-Bi. It is also called poly(butylene adipate-co-terephthalate) and sometimes polybutyrate-adipate-terephthalate or even just "polybutyrate". It is generally marketed as a fully biodegradable alternative to low-density polyethylene, having many similar properties including flexibility and resilience, allowing it to be used for many similar uses such as plastic bags and wraps. It is depicted as a block co-polymer here due to the common synthetic method of first synthesizing two copolymer blocks and then combining them. However, it is important to note that the actual structure of the polymer is a random co-polymer of the blocks shown.
Commodity plastics or commodity polymers are plastics produced in high volumes for applications where exceptional material properties are not needed. In contrast to engineering plastics, commodity plastics tend to be inexpensive to produce and exhibit relatively weak mechanical properties. Some examples of commodity plastics are polyethylene, polypropylene, polystyrene, polyvinyl chloride, and poly(methyl methacrylate) .Globally, the most widely used thermoplastics include both polypropylene and polyethylene. Products made from commodity plastics include disposable plates, disposable cups, photographic and magnetic tape, clothing, reusable bags, medical trays, and seeding trays.
In polymer chemistry photo-oxidation is the degradation of a polymer surface due to the combined action of light and oxygen. It is the most significant factor in the weathering of plastics. Photo-oxidation causes the polymer chains to break, resulting in the material becoming increasingly brittle. This leads to mechanical failure and, at an advanced stage, the formation of microplastics. In textiles the process is called phototendering.
Oxo-biodegradation is a process of plastic degradation utilizing oxidation to reduce the molecular weight of plastic, rendering the material accessible to bacterial and fungal decomposition. To change the Molecular structure in order to break down under sunlight, the plastic can be broken down and eaten by microorganisms. Oxo-biodegradable plastics- composed of polymers such as polyethylene (PE) or polypropylene (PP) -contain a prodegradant catalyst, typically a salt of manganese or iron.
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 adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemicals like natural gas or petroleum; however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.
Biodegradable additives are additives that enhance the biodegradation of polymers by allowing microorganisms to utilize the carbon within the polymer chain as a source of energy. Biodegradable additives attract microorganisms to the polymer through quorum sensing after biofilm creation on the plastic product. Additives are generally in masterbatch formation that use carrier resins such as polyethylene (PE), polypropylene (PP), polystyrene (PS) or polyethylene terephthalate (PET).
Biodegradable athletic footwear is athletic footwear that uses biodegradable materials with the ability to compost at the end-of-life phase. Such materials include natural biodegradable polymers, synthetic biodegradable polymers, and biodegradable blends. The use of biodegradable materials is a long-term solution to landfill pollution that can significantly help protect the natural environment by replacing the synthetic, non-biodegradable polymers found in athletic footwear.
The economics of plastics processing is determined by the type of process. Plastics can be processed with the following methods: machining, compression molding, transfer molding, injection molding, extrusion, rotational molding, blow molding, thermoforming, casting, forging, and foam molding. Processing methods are selected based on equipment cost, production rate, tooling cost, and build volume. High equipment and tooling cost methods are typically used for large production volumes whereas low - medium equipment cost and tooling cost methods are used for low production volumes. Compression molding, transfer molding, injection molding, forging, and foam molding have high equipment and tooling cost. Lower cost processes are machining, extruding, rotational molding, blow molding, thermoforming, and casting. A summary of each process and its cost is displayed in figure 1.
Plastic-coated paper is a coated or laminated composite material made of paper or paperboard with a plastic layer or treatment on a surface. This type of coated paper is most used in the food and drink packaging industry.
Polymateria Ltd is a British technology company developing biodegradable plastic alternatives. In 2020, the privately owned company was the first to achieve certified biodegradation of the most commonly-littered forms of plastic packaging in real-world conditions, in less than a year without creating microplastics.
