Kinetic triplet and thermodynamic parameters of the pyrolysis reaction of invasive grass Eleusine indica biomass: a new low-cost feedstock for bioenergy production

The present paper aims to elucidate the bioenergy potential of the invasive grass Eleusine indica based on its physicochemical characterization, pyrolysis kinetics, and thermodynamic parameters. The pyrolytic behavior of E. indica acquired from non-isothermal thermogravimetric experiments was kinetically represented by three independent parallel reactions, each corresponding to one pseudo-component (pseudo-hemicellulose (P-HC), pseudo-cellulose (P-CL), and pseudo-lignin (P-LG)). The pseudo-components were typified by their kinetic triplets ( E a , A , and f(α) ) and thermodynamics parameters (Δ H , Δ G , and Δ S ). The average activation energy values of E. indica pyrolysis estimated from four isoconversional methods (Friedman, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Starink) varied between 98.5 and 101.8 kJ mol −1 for P-HC, 113.7 and 123.4 kJ mol −1 for P-CL, and 205.3 and 236.0 kJ mol −1 for P-LG. Pre-exponential factors of devolatilization of P-HC, P-CL, and P-LG estimated from the kinetic compensation effect were 1.73 × 10 9 , 6.06 × 10 9 , and 1.16 × 10 19 min −1 , respectively. The most plausible mechanisms for the E. indica pyrolysis included the F2 reaction model for P-HC, the A2 reaction model for P-CL, and the F6 reaction model for P-LG. The cumulative kinetic expression adequately represents the experimental kinetic curves, with R 2 > 0.92 and Fit > 94.9%. Based on the thermodynamic analysis, the positive values of Δ H and Δ G showed that the E. indica pyrolysis was endothermic and nonspontaneous. In contrast, the Δ S was negative, revealing a lower reactive process characteristic. Overall, the results highlight the potential utilization of E. indica for bioenergy production and provide a solid basis for designing pyrolytic reactors using this invasive grass as a feedstock. Graphical abstract