Recycling Renewable resources

In addition to the solid waste problem, we can also expect that with expanding population or expanding demands of a static population, there will be societal pressure to reduce material usage over and above cost factors. These pressures could result in legislation to expand the environmental protection philosophy. For example, since plant materials are a renewable resource as well as readily recyclable, we may expect forced increases in paper-based packages. 

New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

The complete elimination of functional groups is often an undesirable side reaction in organic synthesis, but on the other hand it is a possibility for the recycling of environmentally harmful compounds, for example phenols and haloarenes such as polychlorinated dibenzodioxins (PCDDs or dioxins ). For example, aryl chlorides can be effectively dechlorinated with Pd(0) NPs in tetra-butylammonium salts with almost quantitative conversions also after 19 runs (entry H, Table 1.4) [96]. On the other hand, a C-0 bond cleavage reaction also seems suitable for the fragmentation of sugar-based biomass such as cellulose or cello-biose in that way, sugar monomers and bioalcohol can be derived from renewable resources (entry F, Table 1.4) [164]. 

The increased importance of renewable resources for raw materials and recyclability or biodegradability of the material at the end of its useful life is demanding a shift from petroleum-based synthetics to agro-based materials in industrial applications. Increased social awareness of environmental problems posed by the non-degradable, non-recyclable content of their products is forcing manufacturers to enhance the biodegradable content, which in turn favors a switch to biomaterials [1]. 

In order to decrease human consumption of petroleum, chemists have investigated methods for producing polymers from renewable resources such as biomass. Nature Works polylactic acid (PLA) is a polymer of naturally occurring lactic acid (LA), and LA can be produced from the fermentation of corn. The goal is to eventually manufacture this polymer from waste biomass. Another advantage of PLA is that, unlike most synthetic polymers which litter the landscape and pack landfills, it is biodegradable. PLA can also be easily recycled by conversion back into LA. It can replace many petroleum-based polymers in products such as carpets, bags, cups, and textile fibers. 

As for other recyclable heterogeneous catalysts, zeolites and related materials can also contribute to the development of environmentally friendly processes in the synthesis of bulk and fine chemicals. The concept of a biomass refinery, capable of separating, modifying and exploiting the numerous constituents of renewable resources, is gaining worldwide acceptance today with a very broad outlook. This chapter has attempted to show that this particular area of carbohydrate chemistry is in itself very rich, both in already acquired knowledge and potential future developments. 

Biodegradable materials are created specifically with recyclability or disposal in mind. Recycling techniques for post-consumer biodegradable plastic products have two important features, which distinguish them from conventional polymers their biodegradability or compostability and the use of renewable resources in their manufacture. 

These calculations show that if renewable resources such as lignins are to find use as substitutes for phenol in wood adhesives, the cost differential between these materials must be maximized to attract investment capital. Clearly, the pulp lignins already being produced are likely to be the lowest cost renewable resource available for this purpose. Those generated in the kraft process are already recycled for their fuel value in the recovery furnace and are not easily accessible. There is only one U.S. company selling kraft lignin, and its lowest bulk price is 40 cents a pound (3). 

In some cases, green reactions are based on feedstocks derived from renewable resources that produce highly pure compounds. Another green option is the use of supercritical fluids that are more benign substances (e.g., water, carbon dioxide, and light nonhalogenated hydrocarbons) such fluids can be used as solvents for separations or as media for reactions, and can be easily recovered from the product mixture and recycled. We can also include here the use of ionic systems of nonvolatile salts that are molten at ambient temperature, and that act as solvents or even have a dual role (as catalysts and solvents), without the risk of unwanted vapors. These ionic solvents replace the more hazardous, volatile, and expensive organic solvents used traditionally. 

F. S., Ultrasound characterization of coronary artery wall in vitro using temperature-dependent wave speed, IEEE Trans Ultrason. Ferroelectr. Ereq. Control 50,1474-1485, 2003 Bhardwaj, R Mohanty, A.K., Drzal, L.T. et al.. Renewable resource-based composites from recycled cellulose liber and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) bioplastic. Biomacromolecules 7, 2044-2051, 2006. 

LCI information is collected as a cross-section of all processes as though they are in steady state. The useful life of many products will be measured in the decades. The actual recycling of disposed products may look very different in the future than currently. It would be rational to predict higher recycling of many products in the future, but this opens the analysis to speculation in contrast to a systematic evaluation of current performance. Similarly, for renewable resources there may... 

Renewable resomces are inevitably of great importance in the years to come. There is a never-ending search for better hving conditions for human beings. The more resource materials can be recycled, the richer we will be. Bioconversion of hgnocellulosics, natural and man-made, is an important hnk in that cycle. Extensive use of renewable resources will also slow down continued deterioration of the environment. 

The numerator is the sum of emergy of the non-renewable resources used (AT) and the wastes (both treated and untreated) that is disposed off (Wtw and Wuw). The denominator is the sum of emergy of the renewable feed used (R), the treated and untreated waste recycled within the plant (Wtrn and Wurr" respectively) and the untreated waste obtained from a neighboring plant (Yuw). 

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