Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO2 and its explosion, alkaline hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute- and concentrated-acid hydrolyses, and biological pretreatments.

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Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review.

https://publikationen.bibliothek.kit.edu/1000050288/18451059

Renewable Power-to-Gas: A technological and economic review

With the rising demand for renewable energy and environmental protection, anaerobic digestion of biogas technology has attracted considerable attention within the scientific community. This paper presents a comprehensive review of research achievements on anaerobic digestion developments for biogas production. The review includes a discussion of factors affecting efficiency (temperature, pH, C/N ratio, OLR and retention time), accelerants (greenery biomass, biological pure culture and inorganic additives), reactors (conventional anaerobic reactors, sludge retention reactors and anaerobic membrane reactors) and biogas AD processes (lignocellulose waste, municipal solid waste, food waste, livestock manure and waste activated sludge) based on substrate characteristics and discusses the application of each forementioned aspect. The factors affecting efficiency are crucial to anaerobic digestion, because they play a major role in biogas production and determine the metabolic conditions for microorganism growth. As an additive, an accelerant is not only regarded as a nutrient resource, but can also improve biodegradability. The focus of reactor design is the sufficient utilization of a substrate by changing the feeding method and enhancing the attachment to biomass. The optimal digestion process balances the optimal digest conditions with the cost-optimal input/output ratio. Additionally, establishment of theoretical and technological studies should emphasize practicality based on laboratory-scale experiments because further development of biogas plants would allow for a transition from household to medium- and large-scale projects; therefore, improving stability and efficiency are recommended for advancing AD research.

Review on research achievements of biogas from anaerobic digestion

A mini-review on membrane fouling

Advances in enhanced biological phosphorus removal: from micro to macro scale.

Hydrolysis and acidification of waste activated sludge at different pHs

Decolorization of an azo dye Orange G in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study.

The possibility of converting hydrogen to methane and simultaneous upgrading of biogas was investigated in both batch tests and fully mixed biogas reactor, simultaneously fed with manure and hydrogen. Batch experiments showed that hydrogen could be converted to methane by hydrogenotrophic methanogenesis with conversion of more than 90% of the consumed hydrogen to methane. The hydrogen consumption rates were affected by both P(H₂) (hydrogen partial pressure) and mixing intensity. Inhibition of propionate and butyrate degradation by hydrogen (1 atm) was only observed under high mixing intensity (shaking speed 300 rpm). Continuous addition of hydrogen (flow rate of 28.6 mL/(L/h)) to an anaerobic reactor fed with manure, showed that more than 80% of the hydrogen was utilized. The propionate and butyrate level in the reactor was not significantly affected by the hydrogen addition. The methane production rate of the reactor with H₂ addition was 22% higher, compared to the control reactor only fed with manure. The CO₂ content in the produced biogas was only 15%, while it was 38% in the control reactor. However, the addition of hydrogen resulted in increase of pH (from 8.0 to 8.3) due to the consumption of bicarbonate, which subsequently caused slight inhibition of methanogenesis.

http://www.daba.lu.lv/grozs/Mikrobiologijas/Biol%20Akt%20Probl/Biol%20Aktual%20Probl_Pavasaris%202012/Journal%20club/08_Ksenija%20Elina%20Krista/Arturs%20Gruduls_raksts_2011.pdf

Simultaneous hydrogen utilization and in situ biogas upgrading in an anaerobic reactor

Waste activated sludge hydrolysis and short-chain fatty acids accumulation under mesophilic and thermophilic conditions: Effect of pH

https://orbit.dtu.dk/files/5754141/manuscript-1-30.pdf

Qi Zhou

Papers

Hydrolysis and acidification of waste activated sludge at different pHs

Decolorization of an azo dye Orange G in aqueous solution by Fenton oxidation process: effect of system parameters and kinetic study.

Simultaneous hydrogen utilization and in situ biogas upgrading in an anaerobic reactor

Waste activated sludge hydrolysis and short-chain fatty acids accumulation under mesophilic and thermophilic conditions: Effect of pH

Enhancement of bioenergy production from organic wastes by two-stage anaerobic hydrogen and methane production process.