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Author

Zuzana Mladenovska

Bio: Zuzana Mladenovska is an academic researcher from Technical University of Denmark. The author has contributed to research in topics: Anaerobic digestion & Manure. The author has an hindex of 10, co-authored 17 publications receiving 974 citations.

Papers
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TL;DR: Numbers of cultivable methanogens, estimated by the most probable number (MPN) method, were significantly lower on glucose, acetate and butyrate at the increased operational temperature, while the numbers of hydrogenotrophic methanogen remained unchanged.

229 citations

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TL;DR: The two-step process for treatment and stabilisation of primary sludge was characterized by a 12% higher organic suspended solids removal efficiency and better pathogen reduction effect than the conventional one-step digestion and there would be a significant energy surplus for the system tested.

179 citations

Journal ArticleDOI
TL;DR: In this article, a two-stage 68 degrees C/55 degrees C anaerobic degradation process for treatment of cattle manure was studied, and the performance of a twostage reactor system was compared with a conventional single-stage reactor running at 55 degrees C with 15-days HRT.
Abstract: A two-stage 68 degrees C/55 degrees C anaerobic degradation process for treatment of cattle manure was studied. In batch experiments, an increase of the specific methane yield, ranging from 24% to 56%, was obtained when cattle manure and its fractions (fibers and liquid) were pretreated at 68 degrees C for periods of 36, 108, and 168 h, and subsequently digested at 55 degrees C. In a lab-scale experiment, the performance of a two-stage reactor system, consisting of a digester operating at 68 degrees C with a hydraulic retention time (HRT) of 3 days, connected to a 55 degrees C reactor with 12-day HRT, was compared with a conventional single-stage reactor running at 55 degrees C with 15-days HRT. When an organic loading of 3 g volatile solids (VS) per liter per day was applied, the two-stage setup had a 6% to 8% higher specific methane yield and a 9% more effective VS-removal than the conventional single-stage reactor. The 68 degrees C reactor generated 7% to 9% of the total amount of methane of the two-stage system and maintained a volatile fatty acids (VFA) concentration of 4.0 to 4.4 g acetate per liter. Population size and activity of aceticlastic methanogens, syntrophic bacteria, and hydrolytic/fermentative bacteria were significantly lower in the 68 degrees C reactor than in the 55 degrees C reactors. The density levels of methanogens utilizing H2/CO2 or formate were, however, in the same range for all reactors, although the degradation of these substrates was significantly lower in the 68 degrees C reactor than in the 55 degrees C reactors. Temporal temperature gradient electrophoresis profiles (TTGE) of the 68 degrees C reactor demonstrated a stable bacterial community along with a less divergent community of archaeal species.

114 citations

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TL;DR: The bacterial and archaeal populations identified by t-RLFP analysis of 16S rRNA genes were found to be identical in both systems, however, a change in the abundance of the species present was detected.

102 citations

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TL;DR: The molecular methods--temperature gradient gel electrophoresis (TGGE), cloning library and sequencing of 16S rDNA--showed presence of a restricted number of archaeal species in both reactors, which was phylogenetically most closely related to Methanosarcina siciliae.

84 citations


Cited by
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Journal ArticleDOI
TL;DR: Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first, and several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described.
Abstract: 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.

2,510 citations

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TL;DR: The current state and perspectives of biogas production, including the biochemical parameters and feedstocks which influence the efficiency and reliability of the microbial conversion and gas yield are reviewed.
Abstract: Anaerobic digestion of energy crops, residues, and wastes is of increasing interest in order to reduce the greenhouse gas emissions and to facilitate a sustainable development of energy supply. Production of biogas provides a versatile carrier of renewable energy, as methane can be used for replacement of fossil fuels in both heat and power generation and as a vehicle fuel. For biogas production, various process types are applied which can be classified in wet and dry fermentation systems. Most often applied are wet digester systems using vertical stirred tank digester with different stirrer types dependent on the origin of the feedstock. Biogas is mainly utilized in engine-based combined heat and power plants, whereas microgas turbines and fuel cells are expensive alternatives which need further development work for reducing the costs and increasing their reliability. Gas upgrading and utilization as renewable vehicle fuel or injection into the natural gas grid is of increasing interest because the gas can be used in a more efficient way. The digestate from anaerobic fermentation is a valuable fertilizer due to the increased availability of nitrogen and the better short-term fertilization effect. Anaerobic treatment minimizes the survival of pathogens which is important for using the digested residue as fertilizer. This paper reviews the current state and perspectives of biogas production, including the biochemical parameters and feedstocks which influence the efficiency and reliability of the microbial conversion and gas yield.

2,440 citations

Journal ArticleDOI
TL;DR: Current optimisation techniques associated with anaerobic digestion are reviewed and possible areas where improvements could be made are suggested, including the basic design considerations of a single or multi-stage reactor configuration, the type, power and duration of the mixing regime and the retention of active microbial biomass within the reactor.

1,383 citations

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TL;DR: In this article, a comprehensive state of the art describing the advancement in recent pretreaments, metabolic engineering approaches with special emphasis on the latest developments in consolidated biomass processing, current global scenario of bioethanol pilot plants and biorefinery concept for the production of biofuels and bioproducts.

1,369 citations

Journal ArticleDOI
TL;DR: This paper presents a review of the main sludge treatment techniques used as a pretreatment to anaerobic digestion, and it is likely that low impact pretreatment methods such as mechanical and thermal phased improve speed of degradation, while high impact methods improve both speed and extent of degradation.

1,058 citations