Application of Thermodynamic Methods to the Study of Plant Biomass and Its Components—A Review

This article describes the basics of chemical thermodynamics and its application to the study of plant biomass and its main components, cellulose, hemicelluloses, lignin, etc. The energy potential of various biomass types, as well as biomass-based solid, liquid, and gaseous biofuels, is determined. A method of additive contributions of combustion enthalpies of main components is proposed to calculate the combustion enthalpy of biomass samples. It is also established that the potential of thermal energy of the initial biomass is higher than the energy potential of secondary biofuels released from this biomass. The thermodynamic functions of plant biopolymers are calculated. Moreover, the thermodynamic stability of various crystalline allomorphs of cellulose and amorphous cellulose is studied. The melting enthalpies of crystallites with different types of crystalline structures are estimated. A thermochemical method for determining the degree of crystallinity of cellulose is proposed. The most important biomass components are cellulose and other polysaccharides. The thermodynamics of the enzymatic hydrolysis of polysaccharides and their conversion into glucose are described. In addition, the thermodynamic analysis of the conversion process of glucose into bioethanol is performed. Considerable attention is also paid to the thermochemistry of cellulose alkalization, etherification, and esterification.