Methane recovery from pretreated kudzu residue and sea squirt tunic waste

초록

Kudzu processing residues and sea squirt tunic waste are by-products, but their structural characteristics may limit their application as anaerobic digestion feedstocks. This study evaluated the biochemical methane potential and kinetic responses of kudzu materials and sea squirt tunic fractions subjected to pretreatments. Kudzu raw material and decoction residue were assessed after grinding or freezing, while kudzu juice was evaluated without additional pretreatment. Whole, body, and root fractions of sea squirt tunic were tested with or without autoclave pretreatment at 120 °C for 25 min. Biochemical methane potential assays were conducted at 35 ± 1 °C using substrate loadings determined on a volatile-solids basis. Because the assays used inocula collected at different times, treatment effects were compared within each batch. Freeze-treated raw kudzu and kudzu residue showed methane yields of 308.5 and 241.9 N mL CH₄ g⁻¹ VS, respectively, compared with 143.9 and 140.4 N mL CH₄ g⁻¹ VS for the corresponding ground samples. The acid detergent lignin content decreased from 15% in raw kudzu to 11% in the residue, although this reduction did not correspond to a higher methane yield. Autoclaving increased methane yields of the whole and body sea squirt fractions from 276.0 and 288.7–301.9 and 322.1 N mL CH₄ g⁻¹ volatile solids, respectively, whereas the root fraction showed little response. Pretreatment performance depended on waste fraction and structure. Freeze-treated kudzu showed higher methane yields than the corresponding ground samples, while autoclaving was beneficial for the whole and body fractions of sea squirt tunic. Copyright © 2026. Published by Elsevier B.V.

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