Ethanol energy balance

H. L. MuUer and S. P. Ho, "Economics and Energy Balance of Ethanol as Motor Fuel," paper presented at 1986 SpringAIChE Mational Meeting, New Orleans, La., Apr. 1986. 

Before energy balance is calculated, we need to make mass balance. Figure 9.1 shows the material balance for ethanol and glycerol fermentation. Put simply, mass into the system is equal to mass out of die system. The mass of carbon dioxide is calculated by adding mass of dry cell, mass of glycerol, mass of edianol and mass of water at product stream and then subtracting die sum from die feed stream. As a result, die mass of carbon dioxide is defined. The heat of the reaction is calculated by the following equation ... 

Material and Energy Balances in the Production of Ethanol from Wood... 

The advances made in enzymatic hydrolysis of cellulosic materials (14) are also of interest. This technology involves only moderate temperature processes in simple equipment which promises to be of significantly lower capital cost than the pressure equipment associated with conventional acid wood hydrolysis processes. All of these considerations combined to lead us to study processes for ethanol production from wood, especially in an effort to obtain data for material and energy balances, and possibly for the economics. 

WAYMAN ET AL. Material and Energy Balances in Ethanol Production 185... 

Alcohol recovery from the fermentation brews was less than complete in most cases, which may be attributable to less than ideal conditions. The best yields, 60 to 97% of theory, were obtained with sugars obtained by hydrolysis of cellulosic residues of the autohydrolysis-extraction process. Unextracted pulps, or the hemicellulose solutions, gave poor ethanol formation, which suggests inhibition. In the calculation of material and energy balances which follows, we have assumed 95% yields of ethanol from wood sugars, which is readily achieved in industrial practice and which we believe to be achievable with our wood sugars as well. 

Beck, M. and Bauer, W., Energy balance of ethanol production with a gas-solid fluidized bed fermenter, Bioproc. Eng., 4 (1989) 123-128. 

The energy balance of ethanol in this type of reactor (CSTR type) is flux in - flux out = disappearance by reaction... 

Shapouri, H. Duffield, J.A. Wang, M. The 2001 Net Energy Balance of Corn Ethanol, USDA Office of the Chief Economist Washington, DC, 2004. 

In contrast to the 1.3 1 energy balance of com ethanol, sugarcane-based ethanol has an energy balance of 8 1. Cellulosic ethanol made from prairie and switch-grass has an energy balance of 6 1, and even gasoline has an energy balance ratio of 5 1. Therefore, the overall environmental impact of com ethanol can be worse... 

BASIS 1 mole ethanol produced n = lm°l Energy balance AH = Q = AHr + AH298... 

Pimentel, D., Ethanol fuels energy balance, economics, and environmental impacts are negative, Nat. Resour. Res., 12, 127-134, 2003. 

Shapouri, H., Duffield, J. A., and Graboski, M.S., Estimating the Energy Balance of Com Ethanol, Agricultural Economics Report 721, USDA, Office of the Chief Economist, Washington, DC, 1995. 

Shapouri H, Duffield J, Wang M. The Energy Balance of Corn Ethanol An Update, in Agricultural Economic Report No. 813. United States Department of Agriculture 2002. 

The unfavorable energy balance notwithstanding, the fermentation of ethanol, as well as other chemicals, from lignocellulose hydrolysate is considered highly desirable by some to avoid competition with food production. We note, however, that the large scale processing of waste lignocellulose runs counter to sensible... 

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