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A thermogravimetric approach to resolving carbonate bias in proximate analysis of marine biomass and its implications for hydrothermal carbonization

par Majidi, Rezvan ;Okoro, Oseweuba ;Shavandi, Armin
Référence RRB 2026, International Conference on Renewable Resources & Biorefineries (22: 2026-06-01 to 2026-06-03: Leuven, Belgium)
Publication Publié, 2026-06-01

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Résumé :

Marine biomass residues are increasingly explored as feedstocks for thermochemical valorization; however, their high mineral content, particularly calcium carbonate (CaCO₃) in shell-derived materials, introduces systematic errors in conventional compositional analysis. Proximate analysis, originally developed for coal and lignocellulosic biomass, assumes that volatile matter arises solely from organic decomposition. This assumption fails for carbonate-rich biomasses, where inorganic decomposition contributes significantly to the measured mass loss. To address this limitation, proximate analysis was integrated with thermogravimetric analysis (TGA) to distinguish inorganic and organic mass contributions. Seven seafood processing residues (fish, shrimp, lobster, crab, oyster, mussel, and sea urchin) were characterized using proximate and ultimate analyses, complemented by TGA. Conventional proximate analysis produced non-physical results, including negative fixed carbon values (down to −37%), arising from misattribution of CO₂ released during carbonate decomposition to volatile matter. TGA revealed distinct decomposition regimes, enabling separation of moisture loss (<150 °C), organic decomposition (~150–650 °C), and carbonate decomposition (~650-850 °C). This study, therefore, proposes a generalized TGA-based correction framework that quantitatively separates carbonate-derived mass loss and redefines compositional parameters for carbonate-rich biomass. Shell-dominated residues exhibited carbonate losses exceeding ~40 wt.%, whereas protein-rich tissues showed dominant organic decomposition (up to ~65 wt.%). These compositional differences govern thermochemical behavior and are critical for accurate feedstock evaluation. This misclassification has direct consequences for hydrothermal carbonization (HTC), since HTC operates below carbonate decomposition temperatures and primarily transforms the organic fraction, while inorganic mineral phases are largely retained. As a result, hydrochar yield can be strongly influenced by mineral retention, with inorganic phases accounting for up to ~50 wt.% of the original feedstock mass in carbonate-rich systems. By resolving organic and inorganic contributions, the proposed TGA-based correction approach enables reliable estimation of reactive biomass fractions and supports rational feedstock selection. Crustacean residues (shrimp, lobster, crab) emerge as promising candidates due to their balanced composition, while shell-rich biomass exhibits limited conversion potential for electrode applications without treatment. This work demonstrates the need for mineral-corrected proximate analysis for carbonate-rich marine biomass and establishes TGA as a critical tool for accurate characterization, process design, and feedstock selection in marine biomass valorization.