Anaerobic digestion of native cellulosic wastes

Mahmood

The Scientific World Journal

et al. 2014

197

Anaerobic digestion is the method of wastes treatment aimed at a reduction of their hazardous effects on the biosphere. The mutualistic behavior of various anaerobic microorganisms results in the decomposition of complex organic substances into simple, chemically stabilized compounds, mainly methane and CO2. The conversions of complex organic compounds to CH4 and CO2 are possible due to the cooperation of four different groups of microorganisms, that is, fermentative, syntrophic, acetogenic, and methanogenic bacteria. Microbes adopt various pathways to evade from the unfavorable conditions in the anaerobic digester like competition between sulfate reducing bacteria (SRB) and methane forming bacteria for the same substrate. Methanosarcina are able to use both acetoclastic and hydrogenotrophic pathways for methane production. This review highlights the cellulosic microorganisms, structure of cellulose, inoculum to substrate ratio, and source of inoculum and its effect on methanogenesis. The molecular techniques such as DGGE (denaturing gradient gel electrophoresis) utilized for dynamic changes in microbial communities and FISH (fluorescent in situ hybridization) that deal with taxonomy and interaction and distribution of tropic groups used are also discussed.

Section: Methanogens—key Microorganisms Of the Methane Fermentatiomentioning

confidence: 99%

Microbial Ecology of Anaerobic Digesters: The Key Players of Anaerobiosis

Mahmood

The Scientific World Journal

et al. 2014

197

“…According to Li et al (2011) after releasing cellulose from LCC sheath, the first step of the fermentation process is depolymerisation throughout cellulolytic bacteria, which produce cellulase. Subsequently, the cellulose disintegration products (such as cellobiose and soluble cellulodextrin of higher order) can be transformed into methane and carbon dioxide after a series of transformations (Bhadra et al 1986;Lynd et al 2002;Zhang and Lynd 2005;Jeihanipour et al 2010Jeihanipour et al , 2011.…”

Section: Introductionmentioning

confidence: 99%

Transformation of Miscanthus and Sorghum cellulose during methane fermentation

et al. 2018

The purpose of the paper is designation of the changes in the structure of cellulose after the methane fermentation process of Miscanthus and Sorghum harvested during the growing season and afterwards. The percentage and structure of cellulose before and after fermentation were studied. Investigations into changes of the cellulose structure were conducted by the SEC, FT-IR and XRD methods. The average percentage of cellulose after the growing season for Miscanthus varieties was higher and for Sorghum varieties was lower. As a result of the fermentation, the percentage of cellulose for both investigated species harvested in two growth seasons was lower. The degree of polymerisation for the plants harvested after the growing season was lower for the most feedstock. As a result of the fermentation process, the degree of polymerization increased for each of the investigated feedstock. However, crystallinity of cellulose remained at the same level for Miscanthus and decreased for Sorghum. It was shown that changes were different in the cellulose structure of the compared species.

“…A major disadvantage related to AD of lignocellulosic-type wastes is their low biodegradability. − It has been reported that co-digestion can be an interesting option for improvement in biogas yields during AD of lignocellulosic wastes due to the positive synergisms established in the digestion process by providing a better nutritional balance. − Co-digestion combines two or more organic substrates in order to improve process performance. − Recently, several studies have shown that co-digestion of agricultural wastes with livestock wastes permits the beneficial complementarily in wastes’ characteristics and enhances the methane productivity of biomethanization process. ,,,− Livestock wastes such as pig manure (PM) not only contribute nitrogen and alkalinity but also provide a high microbiological activity, which is able to degrade vegetal fiber. , …”

Section: Introductionmentioning

confidence: 99%

Improvement of Exhausted Sugar Beet Cossettes Anaerobic Digestion Process by Co-Digestion with Pig Manure

2015

Exhausted sugar beet cossettes (ESBC) are one of the main byproducts generated in the sugar industries. The pellets of dried pulp of ESBC used in this study are composed of 85% beet pulp and 15% molasses and have a high lignocellulosic-type organic matter content (91% volatile solids) and a nitrogen deficiency. Mesophilic anaerobic co-digestion in batch of dried pellets of ESBC and pig manure (PM) was studied in this paper for five mixture ratios. The mixtures were selected on the basis of the carbon/nitrogen ratio, leading to ESBC:PM percentages of 0:100, 32:68, 48:52, 72:28, and 100:0. Codigestion increased the methane yield in all cases relative to the digestion of ESBC alone. Acetic and propionic acids were the main volatile fatty acids observed in the tests. Initial accumulation of propionic acid in the reactors with higher ESBC content (and especially for the 100:0 reactor) indicated the difficulties associated with ESBC degradation. The best results were obtained for co-digestion of ESBC and PM in a 32:68 mixture, leading to 103% and 30% improvement in the specific methane production relative to the digestion of ESBC and PM, respectively. Furthermore, this mixture ratio was also optimal to minimize the lagphase period for methane production.