Book excerpt: Biomass in Small-Scale Energy Applications: Theory and Practice presents the current trends in the development of selected biomass-based technologies for distributed energy generation. It describes the methodology, experimental results, and computer simulations with a focus on pilot systems and devices crucial in multiple applications with related environmental/economic issues. It describes which stages of design, development, and application of advanced biomass-based energy devices are critical in order for a given technology to be successful. It includes both technical/practical information and theoretical background related to combustion kinetics, thermodynamics in energy systems, and properties of selected types of biomass, as well as case studies.