Abstract
In this work, different pretreatment methods for algae proved to be very effective in improving cell wall dissociation for biogas production. In this study, the Ulva intestinalis Linnaeus (U. intestinalis) has been exposed to individual pretreatments of (ultrasonic, ozone, microwave, and green synthesized Fe3O4) and in a combination of the first three mentioned pretreatments methods with magnetite (Fe3O4) NPs, (ultrasonic-Fe3O4, ozone-Fe3O4 and microwave-Fe3O4) in different treatment times. Moreover, the green synthesized Fe3O4 NPs has been confirmed by FTIR, TEM, XRD, SEM, EDEX, PSA and BET. The maximum biogas production of 179 and 206 mL/g VS have been attained when U. intestinalis has been treated with ultrasonic only and when combined microwave with Fe3O4 respectively, where sediment were used as inoculum in all pretreatments. From the obtained results, green Fe3O4 NPs enhanced the microwave (MW) treatment to produce a higher biogas yield (206 mL/g VS) when compared with individual MW (84 mL/g VS). The modified Gompertz model (R2 = 0.996 was appropriate model to match the calculated biogas production and could be used more practically to distinguish the kinetics of the anaerobic digestion (AD) period. The assessment of XRD, SEM and FTIR discovered the influence of different treatment techniques on the cell wall structure of U. intestinalis.
Highlights
Due to their high polysaccharide content and low lignin concentration, macroalgae have tremendous potential as a feedstock for bioenergy production [1,2]
The U. intestinalis treated with 10 min ultrasonic produce highest cumulative biogas production 179 mL/g VS, which means that ultrasonic pretreatment could promote the hydrolysis of carbohydrate polymers to reducing sugar
The best biogas productivity was produced utilizing 5 mg/L Fe3O4 magnetic NPs in combination with MW treated macroalgae. These findings showed that Fe3O4 magnetic nanoparticles improved anaerobic digestion, increasing biogas production and organic matter decomposition
Summary
Due to their high polysaccharide content and low lignin concentration, macroalgae (seaweeds) have tremendous potential as a feedstock for bioenergy production [1,2]. Multicellular sea organisms abound in nature, accounting for over half of the world’s biomass population [3,4]. Seaweeds fix atmospheric CO2 for photosynthesis and can multiply quickly, due to a 4-fold higher photosynthetic efficiency than terrestrial biomass [5]. Pretreatment strategies have been investigated to solve the problem of low CH4 productivity. These approaches improve organic matter bioavailability for microbial hydrolysis, reducing hydraulic retention time (HRT) and enhancing biogas production [7,8]
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