Sugar crop feedstocks

Lignocellulose, which comprises the main construction material of plant biomass, accounts for up to 90% of all biomass and is formed in amounts of approximately 1.5 trillion tons per year [12]. Consequently, lignocellulose is much more abundant than available amounts of vegetable oils, starch, and sugar crops. In addition to the high abundance of lignocellulose, it is inedible, and its utilization as feedstock for production of biofuels and chemicals could drastically reduce challenges of food versus fuel production. 

Feedstock Options. Ethanol may be produced via fermentation (with yeast) of 6-carbon or 12-carbon sugars from a number of carbohydrate sources including sugar crops, starch crops, or lignocellulosic materials. 

Producing methanol from biomass or coal costs about twice as much as producing it from natural gas. This encourages the use of nonrenewable petrochemical sources over biomass or coal. Considering the full production cycle, methanol from biomass emits less carbon dioxide than ethanol from biomass. This is because short rotation forestry, the feedstocks of methanol, requires the use of less fertilizer and diesel tractor fuel than the agricultural starch and sugar crops which are the feedstocks of ethanol. 

Feed Preparation Ethanol can be produced from a wide range of feedstock. These include sugar-based (cane and beet molasses, cane juice), starch-based (corn, wheat, cassava, rice, barley) and cellulosic (crop residues, sugarcane bagasse, wood, municipal solid wastes) materials. Indian distilleries almost exclusively use sugarcane molasses. Overall, nearly 61% of the world ethanol production is from sugar crops (Berg, 2004). 

Sugar beet presents low-water, low-quality soil requirements, and less fertilizer than other sugar crops. Residues from sugar beet-based ethanol production, pulp and bagasse, may be used for the production of cellulosic ethanol. A European demonstration plant in Fresno County (Califomia, US) operates with whole beet as feedstock, delivering 75 million liters of bioethanol per year, accounting for a 71 % saving in CO2 emissions (Platform, 2015). 

In bioprocesses, the feedstocks required to grow the catalysts and produce the chemical renewable are generally renewable resources, such as sugar from crops. Conversely, purely feedstocks chemical synthesis relies largely on non-renewable resources such as oil, coal and natural gas. It follows that as non-renewable resources dwindle, it is likely that biotechnology will become increasingly important to the chemical industry. 

The bulkier biomass crops such as wood waste, switchgrass, miscan-thus or other cellulosic feedstocks have less sugar than corn or sugar cane, so it requires more biomass volume to yield the same quantity of ethanol that corn or sugar can produce. 

Both in the USA and the EU, the introduction of renewable fuels standards is likely to increase considerably the consumption of bioethanol. Lignocelluloses from agricultural and forest industry residues and/or the carbohydrate fraction of municipal solid waste (MSW) will be the future source of biomass, but starch-rich sources such as corn grain (the major raw material for ethanol in USA) and sugar cane (in Brazil) are currently used. Although land devoted to fuel could reduce land available for food production, this is at present not a serious problem, but could become progressively more important with increasing use of bioethanol. For this reason, it is important to utilize other crops that could be cultivated in unused land (an important social factor to preserve rural populations) and, especially, start to use cellulose-based feedstocks and waste materials as raw material. 

While this reaction is substantially exothermic (6), it provides an intriguing approach to the production of fuels from renewable resources, as the required acids (including acetic acid, butyric acid, and a variety of other simple aliphatic carboxylic acids) can be produced in abundant yields by the enzymatic fermentation of simple sugars which are, in turn, available from the microbiological hydrolysis of cellulosic biomass materials ( ] ) These considerations have led us to suggest the concept of a "tandem" photoelectrolysis system, in which a solar photoelectrolysis device for the production of fuels via the photo-Kolbe reaction might derive its acid-rich aqueous feedstock from a biomass conversion plant for the hydrolysis and fermentation of crop wastes or other cellulosic materials (4). 

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