<p>Lavender distillation residue is an underutilized lignocellulosic carbon waste with strong potential for value-added conversion to biochar; however, pyrolysis operating windows are often selected using end-point product metrics alone, with limited mechanistic grounding and weak integration of energy and environmental burdens. Here, a 13-run N₂ pyrolysis design space (200–600&#xa0;°C; 10–40&#xa0;°C&#xa0;min<sup>−</sup><sup>1</sup>; 0–30&#xa0;min hold) was evaluated to develop a mechanism-resolved operating-window framework coupling thermal fingerprints, conversion-dependent kinetics, and decision-oriented screening. Thermogravimetric analysis revealed heating-rate-dependent DTG peak migration (<i>T</i><sub>max</sub> ≈ 327 → 364&#xa0;°C for 5 → 40&#xa0;°C&#xa0;min<sup>−</sup><sup>1</sup>). DTG overlap was quantified using constrained multi-peak deconvolution with information-criterion selection, showing <i>β</i>-dependent statistical resolvability (two peaks at 5–10&#xa0;°C&#xa0;min<sup>−</sup><sup>1</sup>; three peaks at 20–40&#xa0;°C&#xa0;min<sup>−</sup><sup>1</sup>) consistent with overlap-limited separability rather than a literal reaction count. ICTAC-aligned isoconversional kinetics (KAS/FWO/Starink/Friedman) indicated regime evolution: apparent activation energies were comparatively stable through <i>α</i> = 0.1–0.6 but increased sharply at high conversion (<i>α</i> = 0.9), consistent with late-stage carbonization where derivative sensitivity increases. Across the matrix, final temperature exerted the dominant first-order control on the yield–carbonization trade-off. To translate mechanistic insight into actionable selection, electricity-normalized indicators and gate-to-gate EF3.0 midpoint burdens were integrated via entropy-weighted TOPSIS, identifying Run 5 as the best-compromise operating point (48.94% yield; 0.85 kWh kg<sup>−</sup><sup>1</sup> char; 2.05 kWh kg<sup>−</sup><sup>1</sup> fixed-C). Imposing an FC ≥ 60% constraint shifted the preferred option to Run 4 (61.67% fixed carbon; 8.16 kWh kg<sup>−</sup><sup>1</sup> fixed-C). Overall, the study provides a reproducible pathway from thermal fingerprinting to kinetic regime diagnosis and energy/LCA-informed operating-window selection, enabling defensible process design for lavender-residue biochar valorization.</p> Graphical Abstract <p></p>

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Mechanism-resolved operating windows for biochar production from lavender distillation residue

  • Ahsanullah Soomro,
  • Anıl Tevfik Koçer,
  • Mahdi Hassan,
  • Didem Balkanlı

摘要

Lavender distillation residue is an underutilized lignocellulosic carbon waste with strong potential for value-added conversion to biochar; however, pyrolysis operating windows are often selected using end-point product metrics alone, with limited mechanistic grounding and weak integration of energy and environmental burdens. Here, a 13-run N₂ pyrolysis design space (200–600 °C; 10–40 °C min1; 0–30 min hold) was evaluated to develop a mechanism-resolved operating-window framework coupling thermal fingerprints, conversion-dependent kinetics, and decision-oriented screening. Thermogravimetric analysis revealed heating-rate-dependent DTG peak migration (Tmax ≈ 327 → 364 °C for 5 → 40 °C min1). DTG overlap was quantified using constrained multi-peak deconvolution with information-criterion selection, showing β-dependent statistical resolvability (two peaks at 5–10 °C min1; three peaks at 20–40 °C min1) consistent with overlap-limited separability rather than a literal reaction count. ICTAC-aligned isoconversional kinetics (KAS/FWO/Starink/Friedman) indicated regime evolution: apparent activation energies were comparatively stable through α = 0.1–0.6 but increased sharply at high conversion (α = 0.9), consistent with late-stage carbonization where derivative sensitivity increases. Across the matrix, final temperature exerted the dominant first-order control on the yield–carbonization trade-off. To translate mechanistic insight into actionable selection, electricity-normalized indicators and gate-to-gate EF3.0 midpoint burdens were integrated via entropy-weighted TOPSIS, identifying Run 5 as the best-compromise operating point (48.94% yield; 0.85 kWh kg1 char; 2.05 kWh kg1 fixed-C). Imposing an FC ≥ 60% constraint shifted the preferred option to Run 4 (61.67% fixed carbon; 8.16 kWh kg1 fixed-C). Overall, the study provides a reproducible pathway from thermal fingerprinting to kinetic regime diagnosis and energy/LCA-informed operating-window selection, enabling defensible process design for lavender-residue biochar valorization.

Graphical Abstract