Understanding the structural and chemical composition of lignin-rich steam-exploded Ludwigia grandiflora during semi continuous anaerobic digestion

Author(s): Pranshu Bhatia
Email (s): bhatiapranshu1995@soka.gr.jp
Institution or organization of origin: Soka University
Country: Japan


Ludwigia grandiflora, an invasive aquatic weed that thrives in waterways, lakes and ponds, has been causing problems like deterioration of water quality, clogging of water streams due to its overgrowth. Therefore, harvesting and appropriate utilisation of the weed is necessary. Anaerobic digestion (AD) is a simple and low-cost treatment that has been intensively applied to aquatic weeds. However, due to the higher lignin content in L. Grandiflora (25.22 ± 4.6%TS), pretreatment is necessary to improve the overall biogas production by making L. grandiflora more degradable. Therefore, steam explosion (SE) pretreatment was performed at 180 °C for 30 min at a severity factor of 3.8 to enhance the overall biogas yield. To understand the overall substrate solubilisation, semi-continuous AD was performed using steam-exploded L. grandiflora as a substrate. The semi-continuous AD was performed using a continuously stirred tank reactor (CSTR) for 98 days with an initial hydraulic retention time (HRT) of 30 days and organic loading rate (OLR) of 0.9 g-VS /L /day. The pH in the CSTR was in the optimum range of 6.5-8.2 and the biogas yield was enhanced with an average of 265 mL /g-VS. However, due to the fluctuations in the biogas yield, the HRT and OLR were changed on day 42 (50 days and 0.5 g-VS /L /day) and day 49 (40 days and 0.7 g-VS /L /day) and 1 M of NaOH was added to the liquid fraction of the steam-exploded L. grandiflora during the latter part of the operation to maintain stability in CSTR.

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