**Abstract**

Lignocellulosic biomass materials are attracting increasing attention as renewable, economical and abundant resources to reduce dependency on petroleum resources. However, chemical and physicochemical properties of these materials (e.g., low density, moisture content, complex and rigid structure, etc.) limit their use. The contents and compositions of cellulose, hemicellulose and lignin polymers in biomass feedstock highly affect the efficiencies of conversion technologies. In aqueous-phase utilization processes, it is necessary to breakdown the starting biomass material into soluble components and release the carbohydrates into hydrolysate for an effective conversion. It is not economical to convert biomass hydrolysates into renewable fuels in high yields if they mostly contain large-sized molecules such as polysaccharides. The chapter describes challenges of lignocellulosic biomass materials usage in biofuel application such as their complexity and diversity, content and composition, low density, moisture content and dissolution difficulties, etc.

**Keywords:** biomass, utilization, conversion, biofuels, challenges
