From results in Tables 10 and 11, the true/intrinsic reaction rate constant (kr) and the effective volatiles diffusivity (Dm) of pine particles during torrefaction can be further estimated, with the results shown in Table 12. It is seen that the Dm values fitted from experimental data are orders smaller than the Knudsen diffusion coefficients Dk shown in Table 9, but they fall into the typical range for gases diffusing through solid materials (10−9 to 10−14 m2 s−1), confirming the speculation that the diffusion of volatiles through the newly created micropores is the dominating mass transfer step in biomass torrefaction process, at least at the early stage of torrefaction.