Abstract
Microalgae biomass has a great potential in search for new alternative energy sources. They can be used as a substrate for the biogas production in anaerobic digestion. When using microalgae, the efficiency of this process is hampered due to the resistant cell wall. In order to accelerate the hydrolysis of cell wall and increase the efficiency of biogas production we applied two different pretreatments - biological and thermal under mesophilic and thermophilic conditions. During biological pretreatment we incubated microalgae with anaerobic hydrolytic bacteria Pseudobutyrivibrio xylanivorans Mz5T. In thermal pretreatment we incubated microalgae at 90 °C. We also tested a combined thermal and biological pretreatment in which we incubated P. xylanivorans Mz5T with thermally pretreated microalgae. Thermal pretreatment in mesophilic and thermophilic process has increased methane production by 21% and 6%, respectively. Biological pretreatment of microalgae has increased methane production by 13%, but only under thermophilic conditions (pretreatment under mesophilic conditions showed no effect on methane production). Thermal-biological pretreatment increased methane production by 12% under thermophilic conditions and by 6% under mesophilic conditions.
Highlights
Global human population growth, rapid technological development, climate changes and depletion of fossil fuels have led to an accelerated search for new renewable energy sources
The highest biogas production under mesophilic conditions resulted from thermal pretreatment of microalgae (TA) with the average production of 452,9 ml per 1 g TVSsubstrate
The results of our study show that thermal pretreatment in mesophilic (37 °C) Biochemical Methane Potential (BMP) assay increased the biogas production by 16% and methane production by 21% in comparison to untreated microalgae (Table 3)
Summary
Rapid technological development, climate changes and depletion of fossil fuels have led to an accelerated search for new renewable energy sources. Renewable energy sources are classified into groups; first generation biofuels (derived exclusively from crops of cultivated plants) and second generation biofuels (derived from lignocellulosic biomass)[2,3,4] have serious flaws, including a great need for arable land and large amount of consumed water. They are creating a lot of pressure on agriculture and have a low productivity, since produced biomass cannot cover global demand.[5]. The main advantages of using algae are low water consumption (they can be grown in salty, waste and non-potable water), possible production on uncultivated areas with high carbon dioxide concentrations, theoretical high photosynthetic efficiency and high productivity.[7,8]
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