User:Polymersrock/draft article
Ia. In the introduction section, I will discuss generally what biodegradable additives are, why they are important, and their role in reducing the amount of plastic waste. A few of the review articles will be useful for this general information section and to highlight the importance of biodegradable plastics and additives to enhance the biodegradability of plastics.[1][2]
Biodegradable additives are additives that enhance the biodegradation of polymers by allowing microorganisms to utilize the carbon within the polymer chain itself.
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, polypropylene, polystyrene or polyethylene terephthalate.
Mechanism of biodegradation
This section will discuss the various mechanisms of biodegradation and microbic degradation. There are a few common mechanisms that are cited throughout the literature: anaerobic, aerobic, direct, indirect.
Aerobic
Anaerobic
Direct
Indirect
**The below information is from the original article:
A simple chemical equation of the process is:
C6H12O6 → 3CO2 + 3CH4
Interpretation of this process is as follows - In most cases, plastic is made up of hydrophobic polymers. Chains must be broken down into constituent parts for the energy potential to be used by microorganisms. These constituent parts, or monomers, are readily available to other bacteria. The process of breaking these chains and dissolving the smaller molecules into solution is called hydrolysis. Therefore, hydrolysis of these high-molecular-weight polymeric components is the necessary first step in anaerobic biodegradation. Through hydrolysis, the complex organic molecules are broken down into simple sugars, amino acids, and fatty acids.
Acetate and hydrogen produced in the first stages can be used directly by methanogens. Other molecules, such as volatile fatty acids (VFAs) with a chain length greater than that of acetate must first be catabolised into compounds that can be directly used by methanogens.
The biological process of acidogenesis results in further breakdown of the remaining components by acidogenic (fermentative) bacteria. Here, VFAs are created, along with ammonia, carbon dioxide, and hydrogen sulfide, as well as other byproducts. The process of acidogenesis is similar to the way milk sours.
The third stage of anaerobic digestion is acetogenesis. Simple molecules created through the acidogenesis phase are further digested by Acetogens to produce largely acetic acid, as well as carbon dioxide and hydrogen.
The terminal stage of anaerobic biodegradation is the biological process of methanogenesis. Here, methanogens use the intermediate products of the preceding stages and convert them into methane, carbon dioxide, and water. These components make up the majority of the biogas emitted. Methanogenesis is sensitive to both high and low pHs and occurs between pH 6.5 and pH 8. The remaining, indigestible material the microbes cannot use and any dead bacterial remains constitute the digestate.[3]
Types of biodegradable Additives
Starch
Experiments have been done on the feasibility of using starch as a biodegradable additive.[4]
Bioaugmentation
Experiments have been done on bioaugmentation - the addition of certain microbial strains to plastics - and its role in increasing biodegradability.[5]
Testing methods of biodegradable additives
The below information is what is included in the current article:
ASTM D5511-12 testing is for the "Anerobic Biodegradation of Plastic Materials in a High Solids Environment Under High-Solids Anaerobic-Digestion Conditions"[6]
ASTM D5526-12 testing is for the "Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions"[7]
ASTM D5210-07 testing is for the "Standard Test Method for Determining the Anaerobic Biodegradation of Plastic Materials in the Presence of Municipal Sewage Sludge"[8]
I propose changing the heading to "Testing of biodegradable additives." These are the headings of the proposed sub-sections (there will likely be more):
Testing methods
This section will include certain tests for crystallinity, morphology, etc.
Testing environments/conditions
Soil Burial
source[4]
Compost[5]
Laboratories performing ASTM testing methods
Will likely remove this section.
- Eden Research Labs
- Respirtek
- NE Laboratories
- NSF
References
- ^ Tokiwa, Yutaka; Calabia, Buenaventurada; Ugwu, Charles; Aiba, Seiichi (2009-08-26). "Biodegradability of Plastics". International Journal of Molecular Sciences. 10 (9): 3722–3742. doi:10.3390/ijms10093722. ISSN 1422-0067.
{{cite journal}}
: CS1 maint: unflagged free DOI (link) - ^ Ahmed, Temoor; Shahid, Muhammad; Azeem, Farrukh; Rasul, Ijaz; Shah, Asad Ali; Noman, Muhammad; Hameed, Amir; Manzoor, Natasha; Manzoor, Irfan (2018-3). "Biodegradation of plastics: current scenario and future prospects for environmental safety". Environmental Science and Pollution Research. 25 (8): 7287–7298. doi:10.1007/s11356-018-1234-9. ISSN 0944-1344.
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: Check date values in:|date=
(help) - ^ "Biodegradable Plastic by Additives". BioSphere Biodegradable Plastic. Retrieved 2012-08-30.
- ^ a b Santonja-Blasco, L.; Contat-Rodrigo, L.; Moriana-Torró, R.; Ribes-Greus, A. (2007-11-15). "Thermal characterization of polyethylene blends with a biodegradable masterbatch subjected to thermo-oxidative treatment and subsequent soil burial test". Journal of Applied Polymer Science. 106 (4): 2218–2230. doi:10.1002/app.26667.
- ^ a b Castro-Aguirre, E.; Auras, R.; Selke, S.; Rubino, M.; Marsh, T. (2018-8). "Enhancing the biodegradation rate of poly(lactic acid) films and PLA bio-nanocomposites in simulated composting through bioaugmentation". Polymer Degradation and Stability. 154: 46–54. doi:10.1016/j.polymdegradstab.2018.05.017.
{{cite journal}}
: Check date values in:|date=
(help) - ^ "ASTM D5511-12". ASTM International. Retrieved 2012-06-30.
- ^ "ASTM D5526-12". ASTM International. Retrieved 2012-06-30.
- ^ "ASTM D5210-07". ASTM International. Retrieved 2012-06-30.