Background: Burning fast-growing trees for energy production can be an effective alternative to coal combustion.
Thus, lignocellulosic material, which can be used to obtain chemicals with a high added value, is highly abundant,
easily renewed and usually inexpensive. In this work, hemicellulose extraction by acid hydrolysis of plant biomass
from three different crops (Chamaecytisus proliferus, Leucaena diversifolia and Paulownia trihybrid) was modelled and
the resulting solid residues were used for energy production.
Results: The influence of the nature of the lignocellulosic raw material and the operating conditions used to extract
the hemicellulose fraction on the heat capacity and activation energy of the subsequent combustion process was
examined.
The heat power and the activation energy of the combustion process were found to depend markedly on the hemicellulose
content of the raw material. Thus, a low content in hemicelluloses resulted in a lower increased energy yield
after acid hydrolysis stage.
The process was also influenced by the operating conditions of the acid hydrolysis treatment, which increased the
gross calorific value (GCV) of the solid residue by 0.6–9.7% relative to the starting material. In addition, the activation
energy of combustion of the acid hydrolysis residues from Chamaecytisus proliferus (Tagasaste) and Paulownia trihybrid
(Paulownia) was considerably lower than that for the starting materials, the difference increasing with increasing
degree of conversion as well as with increasing temperature and acid concentration in the acid hydrolysis.
The activation energy of combustion of the solid residues from acid hydrolysis of tagasaste and paulownia decreased markedly
with increasing degree of conversion, and also with increasing temperature and acid concentration in the acid hydrolysis
treatment. No similar trend was observed in Leucaena diversifolia (Leucaena) owing to its low content in hemicelluloses.
Conclusions: Acid hydrolysis of tagasaste, leucaena and paulownia provided a valorizable liquor containing a large
amount of hemicelluloses and a solid residue with an increased heat power amenable to efficient valorization by
combustion. There are many potential applications of the hemicelluloses-rich and lignin-rich fraction, for example as
multi-components of bio-based feedstocks for 3D printing, for energy and other value-added chemicals.