Biodegradable plastics are plastics that decompose by the action of living organisms, usually bacteria.
Two basic classes of biodegradable plastics exist: Bioplastics, whose components come from renewable raw materials, and plastics made from petrochemicals containing biodegradable additives that enhance biodegradation.
Video Biodegradable plastic
Example
- While aromatic polyesters are almost completely resistant to microbial attack, most aliphatic polyesters are biodegradable because of their hydrolyzed ester bonds:
- Naturally Produced: Polihydroxyalkanoate (PHAs) such as poly-3-hydroxybutyrate (PHB), polyhydroxivalerate (PHV) and polyhydroxyhexanoate (PHH);
- Renewable Resources: Polylactic acid (PLA);
- Synthetic: Polybutylene succinate (PBS), polycaprolactone (PCL)...
- Polyanhydrida
- Polyvinyl alcohol
- Most derivatives of starch
- Cellulose ester such as cellulose acetate and nitrocellulose and its derivatives (celluloid).
- Polyethylene terephthalate
- Biodegradable plastic enhanced with additives.
Maps Biodegradable plastic
Controversy
Many people are confused "biodegradable" with "compostable". "Biodegradable" broadly means that an object can biologically decompose, while "compostable" usually determines that such a process will produce compost, or humus. Many plastic manufacturers throughout Canada and the US have released products indicated as compost. The waste management infrastructure currently recycles regular plastic waste, incinerates it, or places it in landfills. Mixing biodegradable plastics into an ordinary waste infrastructure pose some danger to the environment. However this claim is debatable, if the manufacturer is at least in accordance with the current American Standard definition for Testing and Materials, as it applies to plastics:
"It is capable of performing biological decomposition on the compost site in such a way that the material is not visually distinguished and decomposed into carbon dioxide, water, inorganic compounds and biomass at levels consistent with known compost material." (ASTM D 6002)
There is a big difference between this definition and what is expected from backyard composting operations. With the inclusion of "inorganic compounds", the above definition makes it possible that the final product may not be humus, organic matter. The only standard definition criteria for ASTM do outline is that compostable plastics should be "indistinguishable" at the same level as something that has been defined as compostable under traditional definitions.
Withdrawal ASTM D 6002
In January 2011, ASTM drew the ASTM D 6002 standard, which many plastic manufacturers have been referring to to gain credibility in labeling their products as compost. The description drawn is as follows:
"This guide includes recommended criteria, procedures, and a general approach to establishing compostable plastics that can be degraded environments."
By 2014, ASTM has not replaced this standard.
Advantages and disadvantages
Under appropriate conditions, some biodegradable plastics can be degraded to the point where microorganisms can fully metabolize them into carbon dioxide (and water). For example, starch-based bioplastics produced from sustainable farming methods can be almost carbon neutral.
It is suspected that a biodegradable plastic bag can release metal, and may take a lot of time to degrade under certain circumstances and OBD (oxo-biodegradable) plastic can produce small pieces of plastic that do not continue to decrease at a meaningful level regardless of the environment. The response of the Oxo-Biodegradable Plastic Association (www.biodeg.org) is that OBD plastic does not contain metal. They contain metal salts, which are not prohibited by law and are in fact necessary as trace elements in the human diet. Oxo-biodegradation of polymer materials has been studied in depth at the Technical Research Institute of Sweden and the Swedish University of Agricultural Sciences. The report reviewed by co-workers showed 91% biodegradation in the soil environment within 24 months, when tested in accordance with ISO 17556.
Environmental benefits
There is much debate about total carbon, fossil fuels and water use in the manufacture of bioplastics from natural ingredients and whether they have a negative impact on human food supplies. To make 1 kg (2.2 bp) of polylactic acid, the most commercially available commercial compost, 2.65 kg (5.8 lb) of corn is required. Since 270 million tons of plastics are made annually, replacing conventional plastics with polylactic acid derived from corn will eliminate 715.5 million tons of world food supply, at a time when global warming is reducing tropical agricultural productivity. "Although US corn is a highly productive crop, with typical yields of between 140 and 160 bushels per acre, deliveries produced from food by the corn system are much lower.Crops are currently primarily used for biofuels (about 40 percent of US corn is used for ethanol) and as animal feed (about 36 percent of US corn, plus distillate seeds left over from ethanol production, fed to livestock, pigs and chickens).Most of the remainder is exported Only a small fraction of the national maize crop is directly used for food for Americans, mostly for high fructose corn syrup. "
Traditional plastics made from non-renewable fossil fuels lock most of the carbon in plastic instead of burning in plastic processing. Carbon is permanently trapped inside a plastic grille, and is rarely recycled, if one neglects to insert diesel, pesticides, and fertilizers used to grow food into plastic.
There are concerns that other greenhouse gases, methane, may be released when biodegradable materials, including plastics that are completely biodegradable, are degraded in anaerobic landfill environments. The production of methane from 594 managed landfill environments is captured and used for energy, some of these burning landfills are through a process called combustion to reduce the release of methane to the environment. In the US, most of the currently dumped material is dumped into landfills where they capture methane biogas for use in clean and inexpensive energy. Burning non-biodegradable plastic will release carbon dioxide as well. Disposing of non-biodegradable plastic made from natural ingredients in an anaerobic environment (landfill) will produce a plastic that is resistant for hundreds of years.
Bacteria have developed the ability to degrade plastics. Although not a solution to the disposal problem, it is possible that bacteria have developed the ability to consume hydrocarbons. In 2008, a 16-year-old boy reportedly isolated two bacteria that consumed plastic.
Environmental issues and benefits
According to EPA's 2010 report, 12.4%, or 31 million tonnes, of all municipal solid waste (MSW) are plastics. 8.2% of it, or 2.55 million tonnes, was rediscovered. That's much lower than the average percentage of recovery of 34.1%.
Most of the reasons for this disappointing plastic recycling purpose are that conventional plastics are often mixed with organic waste (food scraps, wet paper, and liquids), which leads to accumulation of waste in landfills and natural habitats. Current use is also difficult and impractical to recycle underlying polymers without expensive cleaning and sanitation procedures.
On the other hand, this mixed organic composting (food waste, yard decoration, and non-recyclable wet paper) is a potential strategy for recovering large amounts of waste and dramatically improving community recycling goals. Remaining recyclable food and wastewater comprises 50 million tons of municipal solid waste. Biodegradable plastics can replace non-degradable plastics in this waste stream, making city composting a significant tool for diverting large amounts of irreparable waste from landfills.
The merged plastic combines the usefulness of plastic (lightweight, durable, relatively low cost) with the ability to fully and fully compost within the industrial composting facility. Rather than worrying about recycling the relatively small amount of plastic mixtures, proponents argue that certified biodegradable plastics can be readily mixed with other organic wastes, allowing for composting of a much larger portion of irreversible solid wastes. Commercial composting for all organic blends then becomes commercially viable and economically sustainable. More municipalities can divert significant amounts of waste from burdened landfill because the entire waste stream can now decompose and therefore is easier to process. This removal from the use of landfills can help to alleviate the problem of plastic pollution.
The use of biodegradable plastics, therefore, is seen as enabling a complete recovery of the large amount of municipal waste sold (through composting aerobics) which until now has not been recoverable in any way other than filling the soil or incineration.
Energy costs for production
Various researchers have conducted extensive life-cycle assessments of biodegradable polymers to determine whether these materials are more energy-efficient than polymers made by conventional fossil-based fuels. Research conducted by Gerngross, et al. estimates that the fossil fuel energy required to produce one kilogram of polyhydroxyalkanoate (PHA) is 50.4 MJ/kg, which coincides with other estimates by Akiyama, et al.. , which estimates the value between 50-59 MJ/kg. This information does not take into account the energy of raw materials, which can be obtained from non-fossil fuel-based methods. Polylactide (PLA) is estimated to have a fossil fuel energy cost of 54-56.7 from two sources, but recent developments in PLo's commercial production by NatureWorks have eliminated some fossil-based energy dependence by replacing it with wind and biomass power. strategy-driven. They reportedly made a kilogram of PLA with only 27.2 MJ of fossil fuel energy and anticipated that this amount would drop to 16.6 MJ/kg at the next generation plant. In contrast, polypropylene and high-density polyethylene require 85.9 and 73.7 MJ/kg, respectively, but these values ​​include energy embedded from raw materials as they are based on fossil fuels.
Gerngross reported 2.65 kg of the total energy equivalent fossil energy (FFE) needed to produce one kilogram of PHA, while polyethylene requires only 2.2 kg of FFE. Gerngross considers that the decision to move forward with biodegradable polymer alternatives will need to consider community priorities related to energy, the environment, and economic costs.
Furthermore, it is important to be aware of the youth of alternative technologies. The technology to produce PHA, for example, is still in current development, and energy consumption can be further reduced by eliminating fermentation steps, or by utilizing food waste as raw materials. The use of alternative crops other than corn, such as sugar cane from Brazil, is expected to reduce energy demand. For example, the manufacture of a fermented PHA in Brazil enjoys a favorable energy consumption scheme in which bagasse is used as a source of renewable energy.
Many biodegradable polymers derived from renewable resources (ie starch-based, PHA, PLA) also compete with food production, since the main raw material is corn. For the US to meet the current output of plastic production with BPs, it will require 1.62 square meters per kilogram produced. While this space requirement can be feasible, it is always important to consider how large the impact of large-scale production is on food prices and the opportunity cost of using land in this mode compared to alternatives.
Rule
United States
In terms of the definition of industry standards ASTM, the United States Trade Commission and the US EPA set the standards for biodegradability. ASTM International defines methods for testing biodegradable plastics, both anaerobic and aerobic, as well as in the marine environment. The responsibility of a special subcommittee to oversee these standards falls on the Committee D20.96 on Eco-Friendly Plastics Products and Bio-based Products. The current ASTM standard is defined as a standard specification and standard test method. Standard specifications make pass or fail scenarios whereas standard test methods identify specific testing parameters to facilitate a specific time frame and biodegradable test toxicity on plastics.
Two testing methods are defined for anaerobic environments: (1) ASTM D5511-12 and (2) ASTM D5526 - 12 Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Condition Both of these tests were used for ISO DIS 15985 to determine biodegradation anaerobic from plastic materials.
See also
Further reading
- Biodegradable Plastics and Marine Litter
- Biological Destruction from Plastics: Challenges and Misconceptions
References
Source of the article : Wikipedia
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