Ethanol energy content

In the first years of gasohol use some starting and driveabiUty problems were reported (19). Not all vehicles experienced these problems, however, and better fuel economy was often indicated even though the energy content of the fuel was reduced. Gasohol was exempted from the federal excise tax amounting to a 0.16/L ( 0.60/gal) subsidy. Without this subsidy, ethanol would be too expensive for use even as a fuel additive. 

There has been a recent revival in interest in the use of ethanol-diesel fuel blends (E-diesel) in heavy-duty vehicles as a means to reduce petroleum dependency, increase renewable fuels use, and reduce vehicle emissions [27]. E-diesel blends containing 10-15% ethanol could be prepared via the use of additives. However, several fuel properties that are essential to the proper operation of a diesel engine are affected by the addition of ethanol to diesel fuel - in particular, blend stability, viscosity and lubricity, energy content and cetane number (increasing concentrations of ethanol in diesel lower the cetane number proportionately) [28]. Materials compatibility and corrosiveness are also important factors that need to be considered. 

In most tissues, this acetyl-CoA is oxidised via the Krebs cycle to provide ATP. One litre of table wine has an energy content of around 3000 kJ, so that in some individuals as much as 10% of the daily energy requirement can be provided by ethanol (see Table 2.3). 

The CASH process was developed by cooperation between Canada, the USA and Sweden. In this method, hydrolysis occurs in two steps with dilute sulfuric acid at a temperature around 200 °C (pressure 8-25 bar) and the fermentation of sugars by yeast to ethanol. It has been shown that by using SO2 and dilute sulfuric acid in two steps, this increases the sugar and ethanol yield, since the amount of inhibitors such as furfural is decreased. The process was developed for raw materials such as sawdust and other residues from trees. The ethanol yield is about 30% of the energy in the raw material and there are also by-products, with up to 40% of the energy content in solid form (lignin), which can be used as biofuel. 

The first law of thermodynamics allows us to rate foods in terms of their energy contents. These are really AH of combustion values. Thus, carbohydrates, fats, proteins, and ethanol yield approximately 4, 9, 4, and 7 kcal/g, respectively when combusted. A normally active person requires between 2000 and 2500 kcal/day in foodstuffs to function normally. Persons doing heavy work may require as much as 5000 kcal/day or more. 

Tl ie energy content of food carboliydrate and food protein is J7 kj/g, whereas that of food fat is 38 kj/g. The energy content of ethanol is 3 kJ/g. Though fairly accurate, these values are only generalizations. For example, consider the energies of different carbohydrates 17,2 kJ/g of starch, 16.6 kJ/g of sucrose, 15,9 kJ/g of glucose. 

The butanols and their methyl and ethyl ethers have several advantages as oxygenates over methanol and ethanol in gasoline blends. Their energy contents are closer to those of gasoline the compatibility and miscibility problems with petroleum fuels are nil excessive vapor pressure and volatility problems do not occur and they are water tolerant and can be transported in gasoline blends by pipeline without danger of phase separation due to moisture absorption. Fermentation processes (Weizmann process) have been developed for simultaneous production of 1-butanol, 2-propanol, acetone, and ethanol from... 

TABLE 14.13 Net Energy Analysis of Ethanol Manufacture in a Modem Integrated Com Production-Fermentation System with and without Co-product Energy Content Credit ... 

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