Hydrogen methane fermentation

Lee, Y.W., Chung, J., 2010. Bioproduction of hydrogen from food waste by phot-scale combined hydrogen/methane fermentation. International Jomnal of Hydrogen Energy 35 (21),... 

In summary the methane fermentation of H2 (Reaction 2) is the only example so far which unequivocally uses COo as a methane precursor, and it may be the only methanogenic component in most other substrate decompositions reported as methane fermentations. There are, however, two examples of methane fermentations where the major methane precursor is never COo but an intact methyl group. In the methane fermentations of acetate and methanol, isotopic labels of the methyl groups are transferred without loss or randomization of their hydrogen substituents, to methane ... 

Methane fermentation in natural ecosystems is usually described as a two-stage system in which nonmethanogenic bacteria ferment organic matter such as carbohydrate yielding such products as acetate, formate, hydrogen, and carbon dioxide. The methanogenic bacteria are restricted... 

Table II contains representative over-all reactions for methane fermentations of acetate and hydrogen, respectively. Acetate fermentation is mediated by heterotrophic organisms which use acetate as a carbon source for synthesis as well as energy. For reaction B , Ek represents the electron equivalents of the electron donor converted for energy per electron equivalent of cells synthesized. Hydrogen fermentation, by contrast, is mediated by autotrophic organisms which use carbon dioxide, acetate, or some other carbon source for cell synthesis. In the equation shown in Table II acetate was assumed to be the carbon source used as found for this fermentation by Bryant (I). E has the same definition as for heterotrophic growth.

Hydrogen Oxidation Kinetics. Shea et al. (22) studied the kinetics of methane fermentation by an enrichment culture of lithotrophic (autotrophic) hydrogen oxidizing methanogenic bacteria at 37 °C. Reported values of the kinetic coeflScients are as follows (1) Y = 0.043 mg volatile suspended solids per mg of hydrogen COD removed, (2) b = —0.009 day"S (3) k = 24.8 mg hydrogen COD removed per mg volatile suspended solids per day and (4) Ks = 569 mm of mercury, hydrogen pressure. 

In this chapter, the early work on methane fermentation, the basic biochemistry and microbiology of the organisms involved, how the process is performed, some of the advancements that have improved the process, and the status of efforts to expand commercial use are discussed. The microbial generation of hydrogen and the factors that have limited its use are also discussed. 

Photosynthetic bacteria can rapidly assimilate volatile fatty acids and grow. Because it assimilates organic compounds, hydrogen production from various fatty acids has been investigated. As for volatile fatty acids, lactate obtained after lactate fermentation of carbohydrates and acetate contained in processed solution after methane fermentation can be used as a substrate. 

There are several ways to produce energy by fermentation, such as methane fermentation, ethanol fermentation and hydrogen fermentation. Of these, methane fermentation is rather organic waste treatment than energy production, while ethanol fermentation is of practical importance under certain conditions as demonstration in Brazil. Hydrogen fermentation is still not in practical use because the energy conversion efficiency from substrates is fairly low (Table 1), and also is not estimated from a suitable point of view for utilization. 

---