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This paper presents data on methane fermentation of algal biomass containing Chlorella sp. and Scenedesmus sp. The biomass was obtained from closed-culture photobioreactors. Before the process, the algae were subjected to low temperature and pressure pretreatment for 0.0, 0.5, 1.0 and 2.0 h. The prepared biomass was subjected to mesophilic methane fermentation. The amount and composition of the biogas formed in the process were determined. The amount of biogas produced was larger when the biomass was subjected to thermal preprocessing. The proportion of methane in the gas also increased. Extending the heating time beyond 1.0 h did not significantly improve the biogassing effects.

Abstract The use of algae as a potential substrate in biogas production processes has been discussed sporadically, therefore this manuscript provides an overview of reference data published so far on that matter. The goal of this review is to present possibilities of applying algae biomass for biogas production purposes and to determine the effectiveness of the fermentation process of algae belonging to various taxonomic groups, originating from various biocenoses and characterized by different morphology and properties. Finally, this work reports on methods and technological solutions for algae biomass production as well as impediments and opportunities stemming from algae biomass use in biogas production technologies.

Hydrogen is an environmentally friendly biofuel which, if widely used, could reduce atmospheric carbon dioxide emissions. The main barrier to the widespread use of hydrogen for power generation is the lack of technologically feasible and—more importantly—cost-effective methods of production and storage. So far, hydrogen has been produced using thermochemical methods (such as gasification, pyrolysis or water electrolysis) and biological methods (most of which involve anaerobic digestion and photofermentation), with conventional fuels, waste or dedicated crop biomass used as a feedstock. Microalgae possess very high photosynthetic efficiency, can rapidly build biomass, and possess other beneficial properties, which is why they are considered to be one of the strongest contenders among biohydrogen production technologies. This review gives an account of present knowledge on microalgal hydrogen production and compares it with the other available biofuel production technologies.

The search for a balance between the energy-related challenges of the future and providing nutritional security has resulted in the development of a market for biofuels of successive generations. The larger their portion in biofuel production, the less the prices of agricultural products will increase. The use of algae, cyanobacteria and aquatic plants in the production of liquid fuels is an alternative. The aim of this study was to determine the effect of thermal hydrolysis on degradation of polysaccharides contained in biomass of cyanobacteria Arthrospira platensis and to assess the effectiveness of ethanol production from preconditioned biomass. The study is aimed at the selection of the most advantageous parameters of thermochemical hydrolysis to reach the experiment variant with the best effects, degree of polysaccharide degradation and effectiveness of alcohol fermentation. The experiment was divided into two stages; in stage I, the possibility of obtaining fermentable sugars by hydrothermal and chemical treatment of the substrate was tested. Stage II involved an assessment of the effectiveness of the pretreatment methods to produce bioethanol in alcohol fermentation. Yeast used in industrial ethanol production-Saccharomyces cerevisiae As4-was used in the alcohol fermentation. The results have shown that the temperature of 150 °C was the most beneficial for the process of thermohydrolysis, and the mash in the microwave-heated sample contained the highest concentration of alcohol (0.97 g/l), which is 98% more than in the control mash and 37% more than in the conventionally heated sample.

Abstract This study aimed to analyze the coupled effect of electromagnetic microwave radiation and sodium hydroxide on the structure of a lignocellulosic complex of Virginia mallow and to determine the susceptibility of the pretreated substrate to anaerobic degradation. Effects of substrate digestion with conventional and microwave heating were compared as well. NaOH dose increase from 0.02 g·gt.s−1. to 0.2 g·gt.s−1. caused biogas production to increase in both heating variants. In turn, NaOH dose increase to 0.4 g·gt.s−1. resulted in diminished biogas production in variants with both microwave and conventional heating, i.e. by 15.3% and 20.8%, respectively. The highest biogas production effectiveness was achieved during fermentation of the substrate conditioned using microwave radiation coupled with the addition of NaOH in a dose of 0.2 g·gt.s−1., and the result obtained was by 10% higher compared to the conventionally-heated sample and by 39.4% higher compared to the microwave-heated and chemically-untreated sample. The coupled use of microwave heating and alkaline treatment allowed achieving a higher volume of biogas produced. Methane content in gaseous bacterial metabolites ranged from 58 to 61%, irrespective of NaOH dose and heating method.

Abstract Biogas production from lignocellulosic biomass e.g. animal manures and agricultural residues may play a fundamental role as renewable energy sources. Many pretreatment methods can be used to prepare these substrates for biogas production. In this study, hydrodynamic cavitation and ultrasound were used for agricultural residues pretreatment to enhance its biomethanization. A small-scale study allowed to assess biogas productivity and energy efficiency for agricultural biogas plant (ABP) with/without cavitation-based pretreatment of cattle manure and wheat straw. Hydrodynamic cavitation pretreatment (HCP) and ultrasonic pretreatment (UP) significantly enhanced biogas production to 430 and 460 L methane/kg volatile solids (VS), respectively. The final net energy output of ABP/ABP-UP/ABP-HCP was respectively 56/52/61 kWh/d (p

Lignocellulosic biomass is included in the group of renewable energy sources. Its calorific value is high, owing to which it can be successfully used in the production of second-generation fuels, e.g., biogas. However, its complex structure makes it necessary to apply a pretreatment in order to increase the biogas output. This study presents the usability of a pulsed electric field in grass silage pretreatment in methane fermentation and compares it with microwave-induced disintegration. The experiment shows that substrate disintegration with a pulsed electric field (PEF) results in an increase in methane output. The productivity of methane from PEF pretreatment silage increased by 20.1% compared to the untreated control. The application of microwave disintegration, with the assumption that the same energy is used for the pretreatment, resulted in a methane output increase of 6% compared to the control. The highest biogas production output in PEF-pretreated samples was 535.57 NL/kg VS, while the highest biogas output from substrates pretreated with microwaves was 487.18 NL/kg VS.

Abstract The selectivity of microwaves against more polar substances lead to unequal heating of material interior, which results in microexplosions that cause degradation of the lignocellulose complex. The thermal effects consists in the generation of internal heat by radiation, which leads to the aforementioned explosions of molecules. In turn, the non-thermal action of microwaves induces vibrations of the polar bonds, which leads to the disruption of polar bonds and acceleration of chemical and physical processes. The high radiation energy leads to structural changes of the lignocellulose biomass, increase the specific surface, minimizes the degree of cellulose polymerization and crystallinity, as well as accelerates hydrolysis of hemicellulose and lignin. Considering the characteristics of the microwave radiation and results of thus-far conducted studies concerning its application in the process of biomass conditioning, there is sound base for undertaking research works on the pre-treatment of Virginia fanpetals biomass before the process of methane fermentation.