Maize feedstocks

Outside of the use of cellulose for papermaking, starch is the most widely used plant-derived carbohydrate for non-food uses. Around 60 million tonnes of raw starch are produced per year for food and non-food uses. The US accounts for most of the world s production, utilising starch from maize, which accounts for over 80% of world production. The starch market in the US is driven by the large isoglucose sweetener market and now increasingly by the growing bioethanol market, which uses maize as a fermentation feedstock. Europe derives most of its starch from wheat and potatoes, which account for 8% and 5% of world starch production, respectively. The other main source of starch is cassava (tapioca), produced in South East Asia. Small amounts of oat, barley and rice are also exploited for starch production. Many edible beans are also rich in starches, but are not commonly exploited for non-food uses. 

Starch is the other carbohydrate-based feedstock. Approximately 10 Mt is produced annually from corn (maize), wheat and potato, out of a total agricultural production of 1.6 Gt a-1 carbohydrate equivalents. A minor fraction of starch is amylose, a linear a 1 ->4 polymer of glucose (Fig. 8.2b). The native structure of amylose is helical loose random coils are formed upon dissolution in water. The branched glucose polymer amylopectin is the major (approximately 75%) component of starch. 

Winterizing is not practiced so widely in hot countries and its application is restricted mainly to sunflower, maize, cotton, ohve, ricebran, and partially hydrogenated soybean oils. The feedstock of the winterizing plant is usually bleached oil, sometimes neutralized or deodorized oil. The winterizing process is conducted in four steps ... 

Straw and Other Crop Residues Crop residues are another source of renewable feedstock that do not find their way into milling processes, especially the residues which are already separated from the crop during or directly after harvesting. For most cereals and oil crops, this Hgnocellulosic biomass is called straw, for example, wheat straw, rice straw, or barley straw. The crop residues of maize are known as corn stover. 

Persson, T., Garcia y Garcia, A., Paz, J., Jones, J., Hoogenboom, G. (2009). Maize ethanol feedstock production and net energy value as affected by climate variability and crop management practices. Agncittora/Syrfemj, 100, 11—21. 

Othors. Triacylglycerols (triglycerides) (10) (70-72) make up a large part of the storage lipids in animal and plant cells. They are now receiving renewed attention as a candidate feedstock for the production of polymer resins. When liquid at room temperature they are called oils. Commercially important oils are produced from the seeds of soybeans, com (maize), cotton, sunflowers, flax (linseed), rape, castor beans, tung, palms, peanuts, olives, almonds, coconuts, and canola. Over 7.3 million metric tons of vegetable oils are produced in the United States each year, mainly from soybean, flax, and rapeseed. Soy oil alone accounts for 80% of the seed oils produced in the United States. Soy oil contains about 55% linoleic acid (11), 22% oleic acid (12) and 10% palmitic acid (13). 

Lactic acid used in the preparation of PLA is derived from annually renewable resources. Cargill Dow uses sugar from maize as feedstock, due to its low cost and abundance, but it is envisaged to use local plant sources containing starch, or sugar, such as wheat, sugar beets or agricultural waste (Fig. 2.5). 

The reported strategy of DuPont is to derive 25% of its revenues from non-depletable resources by 2010. To this end it is reported to have switched production of a key polymer feedstock from a petrochemical to a maize-based process. In the case of Sorona (polytrimethylene terephthalate), the maize-based version is claimed to have environmental advantages over its petrochemical counterpart because the manufacturing process uses less energy, reduces emissions and employs renewable resources. 

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