No description available.

No description available.

Methane is the most abundant organic chemical in the earth's atmosphere. Its abundance in the atmosphere is increasing with time and has reached levels not seen in recent geological history. The methane is produced both naturally, and anthropogenically. One of the sources of anthropogenic methane is manure from domesticated animals. Casada and Safley (1990) estimated the amount of methane generated from this source. This was done by estimating the Methane Conversion Factor (MCF) typically achieved by various waste management systems. This study was done to evaluate those estimates of the MCF. The MCF's for the most dominant of disposal methods, rangeland/pasture disposal, were much lower than the earlier estimates. Other waste management systems, such as solid storage and liquid slurry storage had much higher MCF's, at 20° and 30° C. However, these waste management methods are more prevalent in parts of the world where the average annual temperature is closer to 10° C. At that temperature, the MCF is negligible in all waste management systems. This study showed that the previously reported estimates of MCF for some waste management systems were higher than what was actually the case. Consequently earlier estimates of the amount of methane generated from manures were higher than what this study found. / Graduation date: 1994

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Thesis (Ph.D.) OGI School of Science & Engineering at OHSU, March 2008. / Includes bibliographical references.

Thesis (Ph.D.)--Washington State University, May 2006. / Includes bibliographical references (p. 162-170).

No description available.

The effects of pH upon methane production from anaerobic digestion of dairy cattle manure were investigated. One liter digesters were maintained by daily adjustment at the following pH levels: 7.6, 7.0, 6.0, 5.5, and 5.0. After 33 weeks of incubation the working volume of the digesters was increased to 3 liters. Digesters were incubated on a rotary shaker at 37°C. Digesters were loaded at the desired volatile solids concentrations, without an inoculum, and maintained from day one by daily additions and withdrawals to achieve a 3 day retention time. After 50 weeks of operation the manure from a second dairy was utilized as substrate. Active digestion was achieved at all pH levels except pH 5.0. Biogas production was evident in 4 to 6 days after incubation. Biogas production was highest at pH 7.0 with manure from both dairies (3.047 ± 0.403 liters per liter of digester per day with Dairy II manure and 1.43 ± 0.09 liters per liter per day with Dairy I manure). Methane production was also highest at pH 7.0 (1.43 ± 0.292 liters per liter of digester per day with Dairy II manure and 0.611 ± 0.057 liters per liter per day with Dairy I manure although the highest percentages of methane in the biogas occurred at pH 7.6 (65.9 ± 5.2 from Dairy I manure and 50.4 ± 4.6 from Dairy II manure). Dairy II manure produced significantly more biogas and methane at all pH levels. This increased production could not be attributed solely to differences in volatile solids concentrations of the two substrates. Total volatile acid concentrations were highest at the highest pH levels and were higher with Dairy II manure as a substrate. Digesters at all pH levels had volatile acid concentrations above 2000 mg/liter normally considered inhibitory for methane bacteria (2314-2890 mg/liter with Dairy I manure and 5.708-7.434 mg/liter with Dairy II manure). The results reported here indicate that stable methane digestion of dairy cattle manure can be established maintained at 37°C with a 3 day retention time. Digestion at pH levels as low as 5.5 continued for periods up to 24 months without a failure. High levels of volatile acids did not cause digester failure. Characteristics of the manure have significant effects on biogas and methane production.

Call number: LD2668 .T4 1984 M37 / Master of Science

M. Tech. Civil Engineering / Rural communities in South Africa and Africa as a whole are faced with a problem of the lack of reliable, efficient, sustainable and affordable energy sources. This problem serves as a catalyst to the slow economic development of the rural communities. In order to eradicate the problem and expedite economic development, a need exists to expand energy supply from the national grid or introduce alternative clean, sustainable, environmentally friendly and affordable energy sources to rural areas. However, expanding the national grid would not be sustainable in the long term because 80% of the national grid energy in South Africa is generated from burning fossil fuels, which is neither environmentally friendly nor renewable. The aim of this study was to address the above challenge through scientific investigation of the feasibility of introducing biogas as an alternative source of energy in rural areas. The investigation was to establish a mix ratio of the three types of domestic animal waste namely cow dung, pig dung and chicken droppings, which would optimise biogas production. Biogas, which is a mixture of mainly methane and carbon dioxide gases would in turn be used for cooking. Therefore, the broad objective of the study was to optimise methane gas production through the anaerobic digestion of domestic animal waste.