Starch renewable resources

Polysaccharides are macromolecules which make up a large part of the bulk of the vegetable kingdom. Cellulose and starch are, respectively, the first and second most abundant organic compounds in plants. The former is present in leaves and grasses the latter in fruits, stems, and roots. Because of their abundance in nature and because of contemporary interest in renewable resources, there is a great deal of interest in these compounds. Both cellulose and starch are hydrolyzed by acids to D-glucose, the repeat unit in both polymer chains. 

A rather impressive Hst of materials and products are made from renewable resources. For example, per capita consumption of wood is twice that of all metals combined. The ceUulosic fibers, rayon and cellulose acetate, are among the oldest and stiU relatively popular textile fibers and plastics. Soy and other oilseeds, including the cereals, are refined into important commodities such as starch, protein, oil, and their derivatives. The naval stores, turpentine, pine oil, and resin, are stiU important although their sources are changing from the traditional gum and pine stumps to tall oil recovered from pulping. 

Special mention must be made of poly(lactic acid), a biodegradable/bio-resorbable polyester, obtained from renewable resources through fermentation of com starch sugar. This polymer can compete with conventional thermoplastics such as PET for conventional textile fibers or engineering plastics applications. Hie first Dow-Cargill PLA manufacturing facility is scheduled to produce up to 140,000 tons of Nature Works PLA per year beginning in 200245 at an estimated price close to that of other thermoplastic resins U.S. l/kg.46 Other plants are planned to be built in the near future.45... 

Starch and cellulose are potentially important renewable resources for chemical production. Glucose (a component of starch) is relatively easy to obtain from plant material and is used to synthesize existing chemicals. While this is so, the production of such renewable materials, a full fife-cycle assessment of the requirements for their production suggest that much fossil-soiuced energy and material would stiU be employed in the growing, harvesting and processing of biomass. 

All of these factors mean that production of PHA in plants will likely be more expensive than starch. However, considering that starch costs about 0.25 US /kg, even tripling the production cost of PHA compared to starch would make PHA in plants at least five times cheaper than PHA obtained from bacterial fermentation and most likely the cheapest biodegradable plastic made from renewable resources. 

This kind of plastic is usually made from petroleum, or oil (but polymers are beginning to be made from renewable resources like starch). 

The condition that the biodegradable enabling polyester forms the coherent phase [12] limits the amount of starch and, with this, the amount of renewable resources of pure Ecoflex /starch blends that can be used for the finished film products (typically <50%). An increase in the content of renewable resources can only be achieved by applying (partly) bio-based enabling polyesters (see Sect. 4.1.2 for details of a special grade of Ecoflex - Ecoflex FS). 

The biodegradable polymer available in the market today in largest amounts is PEA. PEA is a melt-processible thermoplastic polymer based completely on renewable resources. The manufacture of PEA includes one fermentation step followed by several chemical transformations. The typical annually renewable raw material source is com starch, which is broken down to unrefined dextrose. This sugar is then subjected to a fermentative transformation to lactic acid (LA). Direct polycondensation of LA is possible, but usually LA is first chemically converted to lactide, a cyclic dimer of LA, via a PLA prepolymer. Finally, after purification, lactide is subjected to a ring-opening polymerization to yield PLA [13-17]. 

Succinic acid is commonly produced in microbes because it exists as a part of the TCA cycle, one of the ordinary metabolic pathways for production of energy. Several groups in the world are developing this production system to produce cheaper succinic acid from renewable resources like starch, glucose, cellulose and so on. If succinic acid could be produced from cheap carbon sources and the price were competitive with the petroleum-base product, many C4 chemicals could be expected as derivatives. 1,4-Butanediol is the typical one, which has a huge market. 

The use of biosolvents, that is, solvents produced from renewable resources (starch and cellulose26), so that the use of fossil resources can be avoided... 

Shogren RL (1998) Starch properties and material applications. In Kaplan DL (ed) Biopolymers from renewable resources. Springer, Berlin Heidelberg New York, p 30... 

Starch is the most readily available and abundant pure carbohydrate. As a continuously renewable resource it has provided a source of energy for human beings and organisms from bacteria to mammalia. The first utilization of modified starch may even precede the discovery of fire. The same may be assumed for the enzymic transformation of starch into alcohol. 

Doi, S., J.H. Clark, D.J. Macquarrie and K. Milkowski, New Materials Based on Renewable Resources Chemically Modified Expanded Corn Starches as Catalysts for Liquid Phase Organic Reactions, Chemical Communications, 2632-2633 (2002). 

Interest in detergent products derived from renewable resources and with better biodegradability has driven evaluation of oxidized sugars and starches as builders or co-builders in detergents.113 Builders and co-builders complex calcium and magnesium ions in hard water to prevent sealing or deposits due to precipitation of insoluble carbonate salts. In current powder detergents, the builders are usually zeolites used in combination with polycarboxylate polymers derived from synthetic acrylic-maleic acid copolymers.114... 

Starch has been considered an attractive raw material for polymer applications for almost 200 years. Kirchoff s discovery in 1811 that treatment of starch with an acid yields a sweet substance was an unexpected result of the search for a low-cost substitute for natural rubber.1 Considerable research in the development of starch-based polymer materials has been stimulated by the facts that starch is produced from wide variety of sources, is an annually renewable resource and is inherently biodegradable. 

Polylactic acid (PLA) is a biodegradable polymer derived from lactic acid. It is a highly versatile material and is made from 100% renewable resources like corn, sugar beet, wheat and other starch-rich products. Polylactic acid exhibits many properties that are equivalent to or better than many petroleum-based plastics, which makes it suitable for a variety of applications. 

The starting material for polylactic acid is starch from a renewable resource such as corn. Corn is milled, which separates starch from the raw material. Unrefined dextrose is then processed from the starch. Dextrose is turned into lactic acid using fermentation, similar to that used by beer and wine producers. 

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