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<p>Water hyacinth (<i>Eichhornia crassipes</i>) is an invasive aquatic weed that presents environmental challenges all around the globe due to its fast growth rate. This water hyacinth can be a potential feedstock for renewable energy, but due to its complex lignocellulosic nature, it inhibits anaerobic digestion (AD). Therefore, this study used juice from this water hyacinth to extract the easily degradable organic matter for biogas production. This study evaluates a crushing–compressing–upflow anaerobic sludge blanket (UASB) approach for the high-rate digestion of water hyacinth juice (WHJ) under carrier-free conditions. The WHJ had a low average pH of around 5.7 with a high concentration of total solids (TS) ranging from 17.4 to 31.6 g·L<sup>-1</sup> and total organic carbon (TOC) ranging from 3.9 to 7.9 g·L<sup>-1</sup>. A laboratory UASB of working volume 6.5 L was operated over 120 days with systematic hydraulic retention time (HRT) reduction from 5, 4, 3 to 2 days and a fed organic loading rate (OLR) ranging from 1.88 to 4.87 g-VSS·L<sup>-1</sup>·d<sup>-1</sup> (0.96 to 3.02 g-TOC·L<sup>-1</sup>·d<sup>-1</sup>). With influent (WHJ)pH adjustment and a stepwise acclimation strategy, stable operation and high treatment efficiency was achieved at HRT of 2 days. The process attained TOC and dissolved organic carbon (DOC) removals of up to 95%, while TS and volatile solids (VS) removals peaked at 76% and 90%, respectively, at shorter HRT. Biogas productivity reached 2.48 m<sup>3</sup>·m⁻<sup>3</sup>·d⁻<sup>1</sup> at the optimum HRT of 2 days, indicating robust performance under intensified loading. It highlights the role of substrate properties in enabling rapid degradation without any additional carrier materials. Mechanistic insights point to Ca–phosphate–driven mineral interactions contributing to biomass retention. Compared with prior WHJ studies and other plant juices, the present work demonstrates a compact, high-rate digestion platform and provides a practical route toward simultaneous weed management and renewable energy recovery. These findings position pressed WHJ or lignocellulosic/aquatic weed juices as a promising feedstock for cost-effective scalable high-rate anaerobic digestion at large scale without any carrier additions.</p>

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High-Rate Digestion of Compressed Water Hyacinth Juice in a Carrier-Free UASB: Pathways to Rapid Organic Removal and Robust Biogas Production

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Pranshu Bhatia,
  • Asuka Kaneda,
  • Masaaki Fujiwara,
  • Masatoshi Kishi,
  • Shinjiro Sato,
  • Tatsuki Toda

摘要

Water hyacinth (Eichhornia crassipes) is an invasive aquatic weed that presents environmental challenges all around the globe due to its fast growth rate. This water hyacinth can be a potential feedstock for renewable energy, but due to its complex lignocellulosic nature, it inhibits anaerobic digestion (AD). Therefore, this study used juice from this water hyacinth to extract the easily degradable organic matter for biogas production. This study evaluates a crushing–compressing–upflow anaerobic sludge blanket (UASB) approach for the high-rate digestion of water hyacinth juice (WHJ) under carrier-free conditions. The WHJ had a low average pH of around 5.7 with a high concentration of total solids (TS) ranging from 17.4 to 31.6 g·L-1 and total organic carbon (TOC) ranging from 3.9 to 7.9 g·L-1. A laboratory UASB of working volume 6.5 L was operated over 120 days with systematic hydraulic retention time (HRT) reduction from 5, 4, 3 to 2 days and a fed organic loading rate (OLR) ranging from 1.88 to 4.87 g-VSS·L-1·d-1 (0.96 to 3.02 g-TOC·L-1·d-1). With influent (WHJ)pH adjustment and a stepwise acclimation strategy, stable operation and high treatment efficiency was achieved at HRT of 2 days. The process attained TOC and dissolved organic carbon (DOC) removals of up to 95%, while TS and volatile solids (VS) removals peaked at 76% and 90%, respectively, at shorter HRT. Biogas productivity reached 2.48 m3·m⁻3·d⁻1 at the optimum HRT of 2 days, indicating robust performance under intensified loading. It highlights the role of substrate properties in enabling rapid degradation without any additional carrier materials. Mechanistic insights point to Ca–phosphate–driven mineral interactions contributing to biomass retention. Compared with prior WHJ studies and other plant juices, the present work demonstrates a compact, high-rate digestion platform and provides a practical route toward simultaneous weed management and renewable energy recovery. These findings position pressed WHJ or lignocellulosic/aquatic weed juices as a promising feedstock for cost-effective scalable high-rate anaerobic digestion at large scale without any carrier additions.