Effects of Different Pretreatments on Improving Biogas Production of Macroalgae Fucus vesiculosus and Fucus serratus in Baltic Sea

Abstract

Global warming along with energy demand and rising prices of natural energy resources have motivated studies to find some renewable and clean energy. The use of algae as the third-generation biofuel can avoid the competition for farmland, and algae can be considered as a potential future source of renewable energy. Algae can be used for biogas production through anaerobic digestion (AD). Fucus vesiculosus and Fucus serratus are the two dominating species of brown seaweed growing in the Baltic Sea in the southwest of Sweden. Pretreatment can significantly affect the biogas production because hydrolysis of the algae cell wall structure is a rate-limiting step in the AD process. In this study, four different pretreatments: mechanical, microwave (600 W, 2 min), ultrasonic (110 V, 15 min), and microwave combined with ultrasonic (600 W, 2 min; 110 V, 15 min) were applied to the seaweed and then codigested with a biogas plant leachate. The aim of this study was to investigate methane yields from AD after these pretreatments. The results showed that when compared with only mechanical pretreatment, the ultrasonic, ultrasonic combined with microwave, and microwave pretreatments could obtain increased cumulative methane yields of 167, 185, and 156%, respectively. The combined pretreatment showed a maximum methane yield of 260 mL/g·of volatile solids after 20 days of digestion. The ultrasonic combined with microwave pretreatment showed a significant improvement in methane yield when compared with the mechanical pretreatment.

Efficiency of Fe3O4 Nanoparticles with Different Pretreatments for Enhancing Biogas Yield of Macroalgae Ulva intestinalis Linnaeus

“…It is clear that the MW treatment only gives the lowest biogas yield among the studied treatment techniques with 84 mL/g VS after 2 min of treatment. Wu [ 16 ] stated that the Microwave pretreatment with a power of 700 W could improve biogas production in the range of 7.8–43.7% when applied for 1.5 min and in the range of 37.2–45.2% when applied for 3 min. However, several studies showed that microwave pretreatment had no or adverse impact on biogas production.…”

“…However, several studies showed that microwave pretreatment had no or adverse impact on biogas production. The small biogas production through microwave pretreatment may be explained by the change in osmotic pressure and the output from solubilization of lignin through microwave pretreatment, which has detrimental effect on anaerobic bacteria [ 16 ]. On the other hand, when comparing the various treatments and the control, the results showed that MW pre-treatment in combination with Fe 3 O 4 NPs produced the best biogas yields.…”

“…The horn is made of titanium alloy with variable power output rates to vary the effect of the ultrasonic application. The ultrasound probe was made with 1/4 inch titanium alloy (5.6 mm and 60 mm height) [ 16 ].…”

“…Using a 0.25 L polytetrafluoroethylene (PTFE) or Teflon lined hydrothermal autoclave reactor containing 150 mL of U. intestinalis algal suspension as the working volume. MW pretreatments were carried out at 1100 watts for two curing times (t) (2, and 4 min) by sharp watts MW system [ 16 ].…”

“…Wu et al [ 16 ] study the effects of different pretreatments (mechanical, US and MW) on improving biogas production of Macroalgae Fucus vesiculosus and Fucus serratus . Pretreatment can significantly affect biogas production because hydrolysis of the algae cell wall structure is a rate-limiting step in the AD process.…”