Spatially homogeneous reactive systems are characterised by the simultaneous presence of a wide range of timescales. When the dynamics of such reactive systems develop very slow and very fast timescales separated by a range of active timescales, with large gaps in the fast/active and slow/active timescales, then it is possible to attain a multi-scale adaptive model reduction along with the integration of the governing ordinary differential equations using the G-Scheme framework. The G-Scheme assumes that the dynamics is decomposed into active, slow, fast, and when applicable, invariant subspaces. We derive expressions that reveal the direct link between timescales and entropy production by resorting to the estimates of the contributions of the fast and slow subspaces provided by the G-Scheme. With reference to a constant pressure adiabatic batch reactor, we compute the contribution to entropy production by the four subspaces. These numerical experiments show that, as indicated by the theoretical derivatio...