This study investigates the pyrolysis behavior of loblolly pine through thermogravimetric (TGA) and derivative thermogravimetric (DTG) analysis under varying nitrogen flow rates of 5–40 mL min⁻¹ and heating rates of 5–20 °C min⁻¹. The pyrolysis proceeded through three distinct phases: Phase I: initial moisture release, Phase II: active devolatilization, and Phase III: char formation. Kinetic modeling using both integral and differential forms of the Coats–Redfern method revealed distinct mechanistic interpretations. The integral approach primarily identified diffusion-controlled models (D1, D3) during moisture and char stages and reaction-order or contraction models (F2, R2) during devolatilization, with activation energies ranging from 8.89 to 70.48 kJ mol⁻¹. In contrast, the differential method captured sharper transitions and favored complex nucleation and growth mechanisms (A3, A4) and power laws (P3, P4), yielding higher activation energies up to 111.29 kJ mol⁻¹ in Phase II. These results underscore the influence of both inert gas flow and thermal ramp on pyrolysis reactivity and demonstrate that kinetic model selection significantly affects activation energy interpretation. The findings contribute to a more nuanced understanding of biomass pyrolysis and offer insights into reactor design and process optimization in thermochemical conversion systems.

Increasing Sargassum accumulation across the Gulf of America and the Caribbean has raised environmental, economic, and public health concerns for coastal communities. As Sargassum decomposes, it can impair tourism, aquatic ecosystems, and air quality, highlighting the need for valorization strategies that convert collected Sargassum into useful products. This study evaluates two carbon-product pathways: Case 1, direct pyrolysis of dried Sargassum at 600.00 °C for 30 min; and Case 2, hydrothermal pyrolysis, in which wet Sargassum was hydrothermally carbonized at 220.00 °C for 30 min before pyrolysis. Process configurations, stream balances, capital costs, manufacturing costs, net present values (NPVs), and breakeven selling price sensitivity analyses were compared. It was seen that Case 1 outperformed Case 2, breaking even in year 5 and achieving a year 12 NPV of over 9.60 million USD, whereas Case 2 never broke even and had a year 12 NPV of −66.04 million USD. A breakeven cost sensitivity analysis showed that Case 1 was sensitive to the Sargassum acquisition cost, while Case 2 was sensitive to the hydrothermal reaction temperature. These results indicated that while direct pyrolysis was economically favorable under the modeled assumptions, hydrothermal pyrolysis could become competitive with additional environmental incentives or carbon credits.

This study investigated the co-combustion behavior of loblolly pine (LP100), kaolin clay (KC100), and LP-KC blends (LP75KC25, LP50KC50, and LP25KC75) using thermogravimetric analysis under air gas flow at heating rates of 5, 10, and 20 °C min⁻¹. The objective was to evaluate how biomass–mineral blending affects thermal degradation, reaction-stage development, kinetic behavior, and thermodynamic properties. The TGA-DTG results were interpreted using Coats–Redfern model-fitting kinetics, Flynn–Wall–Ozawa (FWO) model-free kinetics, and thermodynamic analysis. LP100 and LP-KC blends exhibited two main stages: Phase II oxidative devolatilization and Phase III char oxidation with overlapping kaolinite dehydroxylation, while KC100 showed one dominant high-temperature mineral transformation. In Phase III, the blends’ DTG peak temperatures ranged from 401.7 to 474.3 °C at 5 °C min⁻¹, 427.0 to 500.3 °C at 10 °C min⁻¹, and 478.3 to 509.0 °C at 20 °C min⁻¹. Coats–Redfern Ea values were 58.16–70.50 kJ mol⁻¹ for LP100 in Phase III, and 178.85–181.59 kJ mol⁻¹ for KC100 in Phase III, while the blends’ Ea values ranged from 24.07 to 81.31 kJ mol⁻¹ in Phase II and 30.00 to 59.59 kJ mol⁻¹ in Phase III. FWO analysis confirmed conversion-dependent Ea behavior, with KC100 showing the highest energy barrier. Thermodynamic analysis showed positive ∆G values of 170.59–188.34 kJ mol⁻¹ in Phase II and 197.38–240.84 kJ mol⁻¹ in Phase III. ∆H ranged from 19.67 to 76.55 kJ mol⁻¹ in Phase II and reached 172.53–175.43 kJ mol⁻¹ for KC100 in Phase III, while negative ∆S values of −0.07 to −0.28 kJ mol⁻¹ K⁻¹ indicated ordered activated complexes. In conclusion, LP lowered the apparent kinetic and thermodynamic barriers of KC transformation during co-combustion.