Energy balance fermenter

The energy balance for the bioreactor is shown by the following equation. As the fermenter is used batch wise, the heat balance is mathematically expressed as stated in (4.4.1) ... 

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 ... 

Mass is balanced at the beginning and the end of process. The evaporated water in solid-state fermentation may not be required for energy balance. 

Fermentation systems obey the same fundamental mass and energy balance relationships as do chemical reaction systems, but special difficulties arise in biological reactor modelling, owing to uncertainties in the kinetic rate expression and the reaction stoichiometry. In what follows, material balance equations are derived for the total mass, the mass of substrate and the cell mass for the case of the stirred tank bioreactor system (Dunn et ah, 2003). 

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. 

Their energy needs must be met by balanced fermentations.1383 For example, glutamate may be converted to C02, ammonia, acetate, and butyrate-according to the reactions of Fig. 24-8. The end result is described by Eq. 24-18. 

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... 

The first difficulty in using the energy balance is that enthalpy of formation data may not be available, especially for the biochemical species that are not completely defined. Also, the substrate may be a mixture of substances, and an incompletely characterized mixture of products may be produced in a fermenter. The information that is more likely to be available are the elemental analysis and the heat of combustion (it is relatively easy to put any substance in a calorimeter and measure the heat released on combustion). As a simple example, suppose we wanted to know the enthalpy of benzene at 25 C. We could put one mole of benzene in an isothermal calorimeter with... 

The heat load on the fermenter is found using the energy balance, Eq. 15.9-8,... 

We cannot talk of a return to "renewable sources" and fermentation as the chosen route unless we keep always in mind the Energy Balance. This is the key. 

They do, but the examination must be thorough, factual and not simply wordy. The feedstocks are important, but just as critical is the energy balance. So too are the new tools available to the fermentologist in biogenetics, biochemistry, and biochemical engineering. Fermentation technology has not stood still. But, renewable sources do not necessarily mean economically viable sources. Market surveys plus past experience can help us in our assessments. in the latter cate-... 

Testing of these PHA production technologies in the Pilot Production Facility is a way to determine more accurately physicochentical parameters of fermentation, calculate the material and energy balance, work out technological regulations, and prepare sufficient amounts of the product for investigations, fit a similar effort... 

---