Synergistic and antagonistic interactions in the co-pyrolysis of macadamia nutshells and coffee husks: Thermogravimetric, kinetic, and thermodynamic insights

Q1 Environmental Science

Bioresource Technology Reports Pub Date : 2025-07-07 DOI:10.1016/j.biteb.2025.102207

Ocident Bongomin , Sherien Elagroudy , Josphat Igadwa Mwasiagi , Charles Nzila

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Abstract

The co-pyrolysis of lignocellulosic residues presents a promising pathway for sustainable bioenergy production and waste management. However, the underlying synergistic and antagonistic interactions during co-pyrolysis remain inadequately explored. This study investigates the thermal behavior of macadamia nutshells (MS) and coffee husks (CH) blends (CH75MS25, CH50MS50, and CH25MS75) using thermogravimetric analysis (TGA) under an inert nitrogen atmosphere. The reaction mechanism was evaluated using the Criado's master plot, while activation energy (E_a) and frequency factor (A) were determined via the correlation method and Kissinger method, respectively. Results revealed notable synergistic interactions in the CH50MS50 blend, marked by a 3.8 % reduction in E_a, indicating improved thermal reactivity. This was accompanied by a moderate reduction in E_a (186.94 kJ/mol) compared to MS (191.63 kJ/mol) and CH (183.14 kJ/mol). In contrast, the CH25MS75 blend exhibited antagonistic effects, demonstrated by a 1.96 % deviation and increased energy barriers, attributed to the dominance of lignin-rich MS suppressing volatile release. The A varied from 1.79E+14 min⁻¹ (CH) to 6.21E+14 min⁻¹ (MS), reflecting the inherent thermal stability of each material. Master plot analysis showed that diffusion and nucleation mechanisms (D1, P2) dominated at low conversions, while reaction-order models (F2, F3) prevailed at higher stages. Thermodynamic analysis confirmed the endothermic and non-spontaneous nature of co-pyrolysis, with enthalpy (ΔH) values around 180–190 kJ/mol, entropy (ΔS) up to 0.066 kJ/mol·K, and high Gibbs-free energy (ΔG) values exceeding 150 kJ/mol, indicating notable energy demands and limited spontaneity. These findings provide valuable insights for optimizing biomass blending strategies and advancing co-pyrolysis technologies for efficient bioenergy recovery.

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夏威夷坚果壳和咖啡壳共热解中的协同和拮抗相互作用：热重学，动力学和热力学见解

木质纤维素残基的共热解为可持续生物能源生产和废物管理提供了一条有前途的途径。然而，在共热解过程中潜在的协同和拮抗相互作用仍然没有得到充分的探索。本研究利用热重分析法（TGA）研究了夏威夷坚果壳（MS）和咖啡壳（CH）混合物（CH75MS25、CH50MS50和CH25MS75）在惰性氮气氛下的热行为。采用Criado主图评价反应机理，分别采用相关法和Kissinger法测定活化能和频率因子。结果显示，CH50MS50共混物具有显著的协同作用，Ea降低3.8%，表明热反应性得到改善。与MS （191.63 kJ/mol）和CH （183.14 kJ/mol）相比，Ea （186.94 kJ/mol）有所降低。相比之下，CH25MS75混合物表现出拮抗作用，偏差为1.96%，能量垒增加，这归因于富含木质素的MS抑制挥发性释放的优势。A从1.79E+14 min - 1 （CH）到6.21E+14 min - 1 （MS）不等，反映了每种材料固有的热稳定性。主图分析表明，在低转化阶段，扩散和成核机制（D1, P2）占主导地位，而在高转化阶段，反应级模式（F2, F3）占主导地位。热力学分析证实了共热解的吸热和非自发性质，焓值（ΔH）在180 ~ 190 kJ/mol之间，熵值（ΔS）高达0.066 kJ/mol·K，吉布斯无能高值（ΔG）超过150 kJ/mol，表明共热解的能量需求显著，自发性有限。这些发现为优化生物质混合策略和推进共热解技术以实现高效的生物能源回收提供了有价值的见解。

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