Carbon dioxide biodegradation process

Rayon is unique among the mass produced man-made fibers because it is the only one to use a natural polymer (cellulose) directly. Polyesters, nylons, polyolefins, and acryflcs all come indirectly from vegetation they come from the polymerization of monomers obtained from reserves of fossil fuels, which in turn were formed by the incomplete biodegradation of vegetation that grew millions of years ago. The extraction of these nonrenewable reserves and the resulting return to the atmosphere of the carbon dioxide from which they were made is one of the most important environmental issues of current times. CeUulosic fibers therefore have much to recommend them provided that the processes used to make them have minimal environmental impact. 

Biological. In activated sludge, <0.1% degraded (mineralized) to carbon dioxide after 5 d (Lreitag et ah, 1985). When 1,4-dichlorobenzene was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum, significant biodegradation with gradual acclimation was followed by a deadaptive process in subsequent subcultures. At a concentration of 5 mg/L, 55, 61, 34, and 16% losses were observed after 7, 14, 21, and 28-d incubation periods, respectively. At a concentration of 10 mg/L, only 37, 54, 29, and 0% losses were observed after 7, 14, 21, and 28-d incubation periods, respectively (Tabak et ah, 1981). 

Carbon dioxide is a widely available, inexpensive, and renewable resource. Hence, its utilization as a source of chemical carbon or as a solvent in chemical synthesis can lead to less of an impact on the environment than alternative processes. The preparation of aliphatic polycarbonates via the coupling of epoxides or oxetanes with CO2 illustrates processes where carbon dioxide can serve in both capacities, i.e., as a monomer and as a solvent. The reactions represented in (1) and (2) are two of the most well-studied instances of using carbon dioxide in chemical synthesis of polymeric materials, and represent environmentally benign routes to these biodegradable polymers. We and others have comprehensively reviewed this important area of chemistry fairly recently. Nevertheless, because of the intense interest and activity in this discipline, regular updates are warranted. 

Li XH, Meng YZ, Zhu Q, Xu Y, Tjong SC (2003) Melt processable and biodegradable aliphatic polycarbonate derived from carbon dioxide and propylene oxide. J Appl Polym Sci 89 3301-3308... 

It should be pointed out that the raw materials for VAM and its related polymers (i.e. ethylene and acetic acid) are produced from fossil resources, mainly crude oil. It is possible to completely substitute the feedstock for these raw materials and switch to ethanol, which can be produced from renewable resources like sugar cane, com, or preferably straw and other non-food parts of plants. Having that in mind, the whole production of PVAc, that nowadays is based on traditional fossil resources, could be switched to a renewable, sustainable and C02-neutral production process based on bioethanol, as shown in Fig. 3. If the vinyl acetate circle can be closed by the important steps of biodegradation or hydrolysis and biodegradation of vinyl ester-based polymers back to carbon dioxide, then a tmly sustainable material circle can be established. 

The BAT system operates based on principles of aerobic cometabolism. In cometabohsm, enzymes that the microbes produce in the process of consuming one particular compound (e.g., phenol) have the collateral effect of transforming another compound that normally resists biodegradation (e.g., chlorinated ethenes, especially lesser chlorinated ethenes such as dichloroethene or vinyl chloride). The BAT system operates under these principles by sorbing the chlorinated compounds from a vapor stream onto powdered activated carbon (PAC) where they are cometabolically transformed into a combination of end products, including new biomass, carbon dioxide, inorganic salts, and various acids. 

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