Methane digester

Clostridium populeti was isolated from a wood (poplar) based methane digester by Sleat and Mah (32). Enzymes were evaluated in concentrated/dialyzed medium. 

Officials in San Francisco are hoping the city s pet owners will contribute their animals wastes to a pilot project that will convert organic matter into usable energy. A methane digester converts the wastes into biogas—a mixture of methane and carbon dioxide. Burning the methane provides energy for the city. 

Compare Research and create a pamphlet comparing the advantages of biogas production to other forms of waste disposal for agribusinesses, such as dairies and beef, pork, and poultry producers. Visit glencoe.com for more information about methane digesters. 

Chapter 21 Pooch to Power How a Methane Digester Works. 

It should be pointed out that the performance of the packed-bed methane digester is more dependent perhaps on the influent volatile acids concentration than the overall VS loading rate. Thus, filter performance with acid-digester filtrate might be expected to be better than that obtained with methane-digester effluents having comparable volatile acids content. 

Table VI. STEADY-STATE PERFORMANCE OF CONTINUOUSLY FED MESOPHILIC PACKED-BED METHANE DIGESTER...

The RefCoM (refuse converted to methane) digested mechanically sorted organic fraction in a stirred tank reactor. The retention time was 6-27 days (Chynoweth and Legrand, 1988)... 

Methane digester systems can use almost any wet organic substance to produce as long as the right conditions exist within the digester. Livestock farmers... 

Ana.eroblc Digestion. Methane can be produced from water slurries of biomass by anaerobic digestion in the presence of mixed populations of anaerobes. This process has been used for many years to stabilize municipal sewage sludges for purposes of disposal. Presuming the biomass is all cellulose, the chemistry can be represented in simplified form as follows ... 

Fig. 4. Microbial phases in anaerobic digestion A, hydrolysis B, acidification C, methane fermentation.

Table 37. Potential Methane Production from Commercial U.S. Anaerobic Digestion Systems...

Considerable laboratory work has also been done to develop pre- and post-digestion treatments that improve biodegradabiUty. A plateau of about 50—60% volatile soHds destmction efficiencies and energy recoveries in the product gas seems to exist for most methane fermentation systems. 

Some of the other research studies have addressed topics such as high soHds biomass digestion (154), utilization of superthermophilic organisms (155), advanced reactor designs (156), landfill gas enhancement (157), and microbiology of the mixed cultures involved in methane fermentation (158). 

An anaerobic digester is a no-recycle complete mix reactor. Thus, its performance is independent of organic loading but is controlled by hydraulic retention time (HRT). Based on kinetic theoiy and values of the pseudo constants for methane bac teria, a minimum HRT of 3 to 4 days is required. To provide a safety factor and compensate for load variation as indicated earlier, HRT is kept in the range 10 to 30 days. Thickening of feed sludge is used to reduce the tank volume required... 

Recovery of Riologieal Conversion Products Biological conversion produces that can be derived from solid wastes include compost, methane, various proteins and alcohols, and a variety of other intermediate organic compounds. The principal processes that have been used are reported in Table 25-64. Composting and anaerobic digestion, the two most highly developed processes, are considered further. The recovery of gas from landfills is discussed in the portion of this sec tion dealing with ultimate disposal. 

Anaerobic digestion Methane gas Shredding, air separation Technology on laboratory scale only... 

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