Biomass is one of the most abundant sources of renewable energy and rather than being subjected to direct combustion the attention was recently focused on biomass conversion into liquid energy carriers. Biomass meets all the requirements of renewable and CO2 neutral materials, it is one of the largest sources of energy in the world. Hemicelluloses are heteropolymer with amorphous structure, composed of sugars monomers such as xylose, mannose, glucose, galactose, and others in different ratio depending on feedstocks sources, and make up 20–40% of plant biomass. Triglyceride hydrolysis generates glycerol that is also a major coproduct of bio-diesel production. It can be used to synthetize specialty chemicals, an important source of energy or fuels. A considerable fraction of the nitrogen from proteins will be incorporated into bio-oil during hydrothermal liquefaction. Biomass is decomposed and depolymerized into small components that could be very reactive and they could re-polymerize.