Biomass is plant or animal material that stores both chemical and solar energies, and that is widely used for heat production and various industrial processes. Biomass contains a large amount of the element hydrogen, so it is an excellent source for hydrogen production. Therefore, biomass is a sustainable source for electricity or hydrogen production. Although biomass power plants and reforming plants have been commercialized, it remains a difficult challenge to develop more effective and economic technologies to further improve the conversion efficiency and reduce the environmental impacts in the conversion process. The use of biomass-based flow fuel cell technology to directly convert biomass to electricity and the use of electrolysis technology to convert biomass into hydrogen at a low temperature are two new research areas that have recently attracted interest. This paper first briefly introduces traditional technologies related to the conversion of biomass to electricity and hydrogen, and then reviews the new developments in flow biomass fuel cells (FBFCs) and biomass electrolysis for hydrogen production (BEHP) in detail. Further challenges in these areas are discussed.