Biomass as an alternative source of energy to replace fossil fuels has drawn much attention in recent years. Many of the biomass utilization processes developed in the past later turned out to be ineffective in terms of their energy balance. For example, some publications indicate that the amount of energy needed for the production of biodiesel and bioethanol exceeds the energy derived from the respective fuels.
A systematic development of new processes, avoiding the development of energetically inefficient processes, requires knowledge of the thermodynamic data of the biomass used. Especially for more complex substances like polysaccharides and lignin, these data are not available from the literature, yet.
This research project aimed on the determination of the formation and reaction properties of such biomass compounds. Formation properties like enthalpy and entropy of formation have been determined as well as other thermodynamic properties like heat capacity.
In a succeeding step thermodynamics of reactions utilizing biomass as a feedstock have been analyzed. A group of model reactions, such as the conversion of saccharides to hydrogen or methane or the transformation of lignin into biofuels have been evaluated. By balancing enthalpy and Gibbs’ energy of the respective reactions, the equilibrium yields and conversions have been estimated. The first reaction has already been implemented as a high temperature process. Since in terms of energy, it is desired to carry out reactions at mild conditions, the feasibility of doing this was researched from the thermodynamic viewpoint.
It could be shown that e.g. the production of gaseous products such as hydrogen or methane from saccharides at low temperatures is thermodynamically possible. The equilibrium yield can be further increased by adding an inert gas. This is due to a dilution effect, which lowers the fugacities of the gaseous products.
This project has been supported by the Deutsche Forschungsgemeinschaft (Projektnummer: AR 236/34-1).