Kinetics of lignocellulosic biomass pyrolysis-a pathway for conversion to renewable fuels/chemicals-is transient; discreet changes in reaction rate occur as biomass composition changes over time. There are regimes where activation energy computed via first order Arrhenius function yields a negative value due to a decreasing mass loss rate; this behavior is often neglected in the literature where analyses focus solely on the positive regimes. To probe this behavior feed corn stover and cocoa

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... ls were pyrolyzed at 10K/min. The activation energies calculated for regimes with positive apparent activation energy for feed corn stover were between 15.3 to 63.2 kJ/mol and for cocoa shell from 39.9to 89.4 kJ/mol. The regimes with a positive slope (a "negative" activation energy) correlate with evolved concentration of CH 4 and C 2 H 2. Given the endothermic nature of pyrolysis, the process is not spontaneous, but the "negative" activation energies represent a decreased devolatilization rate corresponding to the transport of gases from the sample surface.