The chemical and structural changes that take place during
torrefaction of biomass were elucidated by using a series
of complementary methods. Torrefaction induced the formation
of acid-insoluble residues by the formation of condensed
aromatic structures. The increased aromaticity and amount of nonprotonated
aromatic carbon were quantified by solid-state NMR
experiments, indicating larger aromatic clusters in TC. This study
on the chemical and structural changes in biomass during torrefaction
present a unique opportunity to reveal the complex and
heterogeneous thermal transformation of torrefied biomass using
complementary tools, including recently introduced 13C DP/MAS
NMR analysis.