Bacterial hydrolysis and methane fermentation of lignocellulosic materials
In order for methane fermentation of lignocellulosic materials to be an effective method for providing both a renewable energy source and a means to reduce the volume of municipal solids wastes, a better understanding of the fermentation process is required, because this process has been generally observed to be a slow and incomplete one. This dissertation focused on understanding of the rate-limiting mechanisms of methane fermentation, including the influence of the type of lignocellulosic materials, bacterial culture characteristics, bacterial concentration, pH, and temperature. Lignocellulosic materials selected for this study were: corn stover, wheat straw, napier grass, wood grass, newspaper, and white fir. Four methanogenic cultures grown on monosaccharides, purified holocellulose, wheat straw, and mixed municipal sludge, respectively, were developed at 35[degrees]C and neutral pH. Each of the four bacterial cultures developed a glucose and cellobiose consumption potential higher than the methanogenic potential, which in turn was higher than the lignocellulosic hydrolysis potential. Further examination of lignocellulosic hydrolysis revealed that it is the step in which bacteria and enzymes can have access to holocellulosic polymers that limits the hydrolysis rate. Microscopic examination revealed that hydrolysis appears to have occurred only at the points of physical contact between the hydrolytic bacteria and the particle surface. Both fermentation rate and extent were greatly influenced by the lignocellulosic material used and by pH and temperature, but they were much less affected by the bacterial culture employed. Lignocellulosic hydrolysis reached a maximum rate at relatively low bacterial concentrations. Both hydrolysis and fermentation processes can be adequately modeled by a first-order rate equation. Linear correlations between lignin content and biodegradability or methane conversion rate were very poor.
- Research Organization:
- Stanford Univ., CA (United States)
- OSTI ID:
- 5622933
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
BACTERIA
MULTI-PARAMETER ANALYSIS
FERMENTATION
LIGNIN
HYDROLYSIS
MUNICIPAL WASTES
BIOCONVERSION
CELLOBIOSE
ENZYMES
GLUCOSE
METHANE
MONOSACCHARIDES
RENEWABLE ENERGY SOURCES
ALDEHYDES
ALKANES
CARBOHYDRATES
CHEMICAL REACTIONS
DECOMPOSITION
DISACCHARIDES
ENERGY SOURCES
HEXOSES
HYDROCARBONS
LYSIS
MICROORGANISMS
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
POLYSACCHARIDES
PROTEINS
SACCHARIDES
SOLVOLYSIS
WASTES
090900* - Biomass Fuels- Processing- (1990-)
320604 - Energy Conservation
Consumption
& Utilization- Municipalities & Community Systems- Municipal Waste Management- (1980-)