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Thermo-acid and thermo-alkaline solubilization of Ulva biomass under mild-temperature conditions
( Heejung Jung ),( Jaai Kim ),( Changsoo Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2014 한국폐기물자원순환학회 심포지움 Vol.2014 No.2
The worldwide attention to biomass as a renewable energy resource is gradually increasing in recent years. Seaweeds are considered a promising next-generation biomass feedstock for biofuel production due to their high content of readily biodegradable carbohydrates. However, the rigid cellular structure hinders efficient utilization of seaweed biomass, and various pretreatment methods have been applied to enhance the hydrolysis rate. This study investigated the effects of thermo-acid and thermo-alkaline pretreatment methods on Ulva solubilization. Ulva, a green macroalgal genus, is known to often cause serious marine green tides, posing environmental concerns, worldwide. Ulva biomass collected from a local beach was thermo-chemically pretreated using HCl or NaOH under mild-temperature conditions (<100℃). Response surface analysis (RSA) was used to statistically examine and compare the effects of the pretreatment methods tested, with the explored chemical dose and temperature ranges of 0 - 200 mM and 50 - 90℃, respectively. Solubilization of Ulva biomass was demonstrated by increases in both soluble chemical oxygen demand (SCOD) and dissolved total nitrogen (DTN) levels. Up to 130% and 790% increases respectively in SCOD and DTN were observed in alkali-treated trials while up to 81% and 395% increases respectively in SCOD and DTN were in acid-treated trials. The response surface models constructed for each pretreatment method showed that thermo-alkaline pretreatment was more effective than thermo-acid treatment on the solubilization of Ulva biomass under the mild-temperature conditions used in this study. It was statistically shown by RSA that NaOH concentration had a much greater effect on the solubilization rate than did temperature within the explored experimental region.
Jung, Heejung,Kim, Jaai,Lee, Changsoo Elsevier 2017 Algal research Vol.28 No.-
<P><B>Abstract</B></P> <P>This study investigated the anaerobic digestion of <I>Ulva</I> biomass as an approach to diversifying energy sources and managing seaweed waste in a cost-effective manner. <I>Ulva</I> species are often identified as the main culprit of serious macroalgal blooms around the world, and their sulfur-rich nature causes difficulties in handling the biomass. Two reactors in continuous (Rc) and sequencing batch (Rs) modes were operated with decreasing hydraulic retention time in a stepwise manner from 20 to 6days. Rs allowed significantly higher methane productivity (0.19–0.22L/g chemical oxygen demand [COD] fed) and biomass retention capacity than Rc (0–0.16L/g COD fed) throughout the experiment. Interestingly, sulfide production was also higher in Rs than in Rc. These findings, together with microbial quantification results, suggested that Rs operation enhanced biomass retention and the activity of both methanogens and sulfate-reducing bacteria. The Rc microbial community was less diverse and more variable than the Rs community. Accordingly, the performance of Rc was more significantly affected by changes in hydraulic and thus organic loads. Aceticlastic <I>Methanosaetaceae</I> dominated the methanogen community in both reactors, with the abundance of methanogens being significantly higher in Rs than in Rc. This may explain the more efficient and stable methane production despite the greater sulfidogenic activity in Rs, particularly at high hydraulic loads. Together, the results suggest that sequencing batch operation is advantageous over conventional continuous flow operation for the biomethanation of <I>Ulva</I> biomass and potentially other sulfur-rich feedstocks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Ulva</I> biomethanation was examined in continuous versus sequencing batch operations. </LI> <LI> Both sulfate-reducing and methanogenic activities were higher in sequencing batch. </LI> <LI> Aceticlastic <I>Methanosaetaceae</I> dominated the methanogen community in both reactors. </LI> <LI> Sequencing batch is advantageous for stable <I>Ulva</I> digestion at high organic loads. </LI> <LI> Sequencing batch is more suitable for the biomethanation of sulfur-rich feedstocks. </LI> </UL> </P>