Fast pyrolysis and related catalytic pyrolysis are of increasing interest as pathways to advanced drop-in biofuels. This book explores several unresolved, and sometimes controversial, questions about the thermal deconstruction of biomass under conditions of fast pyrolysis and catalytic pyrolysis. It is ideal for researchers and industrialist working in pyrolysis and biofuels, this book stimulates discussion on the various competing theories of thermal deconstruction of plant polymers.