Recently, renewable energy sources (RES) have become very popular all over the EU. Subsidy policies have provided huge amount of money flowing into the sector which were necessary for its development. In Slovakia, favourable legislation was one of triggers for building biogas plants using anaerobic fermentation for biogas and further electric energy production. This paper examines how subsidy policy has stimulated biogas sector over the years and the consequences arising from the legislation.
The economics of biogas plants have an impact on the justification of the industrial unit. The conditions of high-yielding high-quality biogas production are estimated on the basis of laboratory fermentation studies. In designing the laboratory fermenters, working conditions must be modelled. However, the biggest problem with the biological model is its size, because the magnitude is less than in industrial applications and therefore extremely sensitive to environmental influences. During the design, an important aspect is that the periodic mixing of the raw material can be done in the reactors as in the industry. This article shows the equipment based on empirical research.
The construction of domestic continuous bioreactor is proposed. The modeling of thermal modes of household biogas plant using graph theory was done. The correction factor taking into account with the influence of variables on its value was determined. The system of balance equations for the desired thermal conditions in the bioreactor was presented.
The graphical and analytical capabilities were represented that can be applied in the design of domestic biogas plants of organic waste recycling.
Jan Loskot, Marek Smolík, Lidmila Hyšplerová, Karol Radocha, Jan Kříž, Stanislav Eminger, Agnieszka Dołhańczuk-Śródka, Zbigniew Ziembik and Maria Wacławek
dust. Int J Res Eng Technol. 2014;3(7):248-254. http://esatjournals.net/ijret/2014v03/i07/IJRET20140307042.pdf .
 Echiegu EA. Kinetic models for anaerobicfermentation processes - A review. Amer. J. Biochem. Biotechnol. 2015;11(3):132-148. DOI: 10.3844/ajbbsp.2015.132.148.
 Yu L, Wensel PC, Ma J, Chen S. Mathematical modeling in anaerobic digestion. J Bioremed Biodeg. 2013;S4(003):1-12. DOI: 10.4172/2155-6199.S4-003.
 Kříž J, Hyšplerová L, Smolík M, Eminger S, Vargová A, Keder J, et al. Modelling of emissions from large biogas plants
Dragos Dracea, Augustina Tronac and Sebastian Mustata
World energy systems development is based on the use of renewable sources, their valorisation benefits of technical and economical stimulating actions. The main disadvantage is related to the low efficiency caused by low energy density and high value investments. The cost of renewable energy is higher than energy coming from conventional sources. Reducing the costs of producing unconventional energy can be achieved by integrating economic and social activities into the system, providing futher benefits. From the potential point of view, it is estimated that biomass occupies the first place in a ranking of unconventional energies. Biomass boosted by anaerobic fermentation with biogas production and cogeneration can provide "peak" energy production and can balance energy systems. Waste utilized by these processes involves reducing environmental impacts by diminushing managed volumes and efficient control. In the present paper are characterized by calculations aspects of the exploitation and elements regarding the optimization of some high-capacity fermenters of a wastewater treatment system.
Ádám Nándor Makk, Tamás Rétfalvi and Tamás Hofmann
Fossil fuel depletion has led to an increasing number of research studies and applications focusing on renewable energy, such as different types of biomass. Lignocellulosic biomass represents an abundant source of biomass suitable for energy production in various forms. The present research investigates the application possibility of pedunculate oak bark (Quercus petrea (Matt.) Liebl.) for the production of biogas via anaerobic digestion. This research has significant novelty, as only a few examples on the utilization of tree bark wastes for the production of biogas can be found in the scientific literature. One of the key factors of increasing biogas yield is the efficient hydrolysis of the basic material, which is achieved by different pretreatment methods. In this study, oak bark was pretreated by microwave energy, by extraction, and by the combination of these two methods. The semi-continuous thermophylic anaerobic digestion of untreated oak bark resulted a 76.3 ml/g volatile solid specific methane yield over a 50-day period, which was not significantly lower than methane yield gained from pretreated basic material. Results indicated that oak bark is suitable for the production of biogas even without the application of the investigated pretreatment techniques. As extraction of oak bark does not impair biogas production, the complex biorefinery utilization of oak bark in the form of extraction bark polyphenols and the subsequent anaerobic fermentation of lignocellulosic residue can be accomplished in the future.
The selected techniques were reviewed and their technological aspects were characterized in the context of multi-phase flow for biogas production. The conditions of anaerobic fermentation for pig slurry in a mono-substrate reactor with skeleton bed were analysed. The required technical and technological criteria for producing raw biogas were indicated.
Design and construction of the mono-substrate model, biogas flow reactor, developed for cooperation with livestock buildings of various sizes and power from 2.5 kW to 40 kW. The installation has the form of a sealed fermentation tank filled with a skeletal deposit constituting a peculiar spatial system with regular shapes and a rough surface.
Incorporating a plant in such a production cycle that enables the entire slurry stream to be directed from the cowshed or pig house underrun channels to the reactor operating in the flow mode, where anaerobic digestion will take place, allows to obtain a biogas.
The paper presents preliminary results of experimental investigations in the field of hydrodynamic substrate mixing system for biogas flow assessment by the adhesive bed in the context of biogas production. The aim of the study was to assessment and shows the influence of the Reynolds number on the biogas resistance factor for the fermentation process in mono-substrate reactor with adhesive deposit. The measurement results indicate a clear effect of the Reynolds number in relation to the descending flow resistance coefficient for the adhesive bed.
The article reviews the energy potential of microalgae as an alternative raw material for anaerobic digestion. Currently, energy security is one of the main topics among researchers. The amount of generated fossil fuels is limited, it is a question of time when fossil fuels will not continue to be accessible at low cost. There is a need to find an alternative carrier of energy which will replace the fossil fuels in the World. Green microalgae can be proposed as a possible bio raw-material, which can be used as an input material in order to produce energy. Lots of alternative technologies of algae cultivation are currently being developed all over the world. There is a necessity to search for a sensible way to produce algal biomass for bioenergy purposes, while maintaining all requirements involved in environmental and economic issues. The research results presented in the science article show that microalgae biomass is the proper alternative material for biogas production with the method of anaerobic fermentation. We believe that these research results can contribute to the future development of all forms of renewable energy in the Slovak Republic.
Five bacterial isolates were tested for their ability to generate hydrogen during anaerobic fermentation with various carbon sources. One isolate from sheep rumen was identified as Escherichia coli and four isolates belonged to Clostridium spp. Glucose, arabinose, ribose, xylose, lactose and cellobiose were used as carbon sources. Results showed that all bacterial strains could utilize these compounds, although the utilization of pentoses diminished growth yield. The excretion of monocarboxylic acids (acetate, propionate, formiate, butyrate) into medium was changed after replacing glucose by other carbon sources. Di- and tricarboxylic acids were excreted in negligible amounts only. Spectra of excreted carboxylic acids were unique for each strain and all carbon sources. All isolates produced H2 between 4—9 mmol·L−1 during the stationary phase of growth with glucose as energy source. This value was dramatically reduced when pentoses were used as carbon source. Lactose and cellobiose, starch and cellulose were suitable substrates for the H2 production in some but not all isolates. No H2 was produced by proteinaceous substrate, such as blood. Results show that both substrate utilization and physiological responses (growth, excretion of carboxylates, H2 production) are unique functions of each isolate.