The use of fossil fuels has been a great driver for the development of the society, as this resource is exhausted, the necessity to make a transition toward a sustainable energetic scheme becomes more evident. This sustainable scheme should be based on the use of several energy sources and between them with a great importance the renewable energy sources. 
Among the renewable energy sources, the biomass represents an important option to substitute the use of fossil fuels, specially in the transport sector because it can be transformed into a liquid fuel that can be use in internal combustion engines, into electricity for electric vehicles or into hydrogen for fuel cell vehicles. 
The future biofuels most be sustainable in technological, economical, environmental and social terms to be able to play an important role. Is in this scenario where the second generation biofuels grow on importance. The biorefineries, an analogue concept of the conventional refineries (which object is to produce fuels, chemical products and electricity), are under research as systems that contribute to increase the participation of biomass not only within the energy market but also in the chemical derivatives market.
The huge amount of biomass that cannot be used in the first generation biofuels production facilities represents a low cost and great availability income for the second generation biorefineries that could increase the possibility of setting up facilities big enough to become economically and environmentally sustainable.
The termochemical biorefineries are one of the biorefineries platforms that fit better to the residues available in the Valencian Community and this platform will let use agricultural and forestry residues to transform them into second generation biofuels and helping with this to reduce the energetic dependency of the Community toward fossil fuels.
In this context, this work of thesis has as main object to evaluate and optimize several concepts of thermo-chemical biorefineries and identify which of the concepts proposed has better technical and economical conditions, considering the available biomass in the Valencian Community.
This work is divided into five chapters, on the first chapter is shown a brief introduction of the energy landscape and also of the different processes where the biomass can be used as an energy source. On the second chapter is presented an introduction to the use of biomass to produce energy using biorefineries by reviewing the different biorefineries concepts known. The third chapter is dedicated to the description of the thermochemical biorefineries to produce Fischer-Tropsch biofuels, hydrogen and electricity, which are the processes to transform the biomass proposed in this work. On the fourth chapter are described the thermochemical biorefineries concepts modelated on this thesis, as well as the component models that were used to simulate the production of the desired energy products. The fifth chapter shows the results of the simulation for the different biorefineries concepts proposed and is made an analysis of the results.
The most outstanding results shown that using the biomass resources available in the Valencia Community it can be installed an energy facility with a capacity of 313 MW considering a plant operation time of 8000 hours per year. From the analysis of the gasification process it was found that the properties of the synthesis gas obtained from different types of biomass are relatively similar among them and the gasification efficiency is between 76% and 79%. From the proposed biorefineries concepts, the most efficient is the production of hydrogen using an IGT gasifier which reaches an energy efficiency of 53%, but the concept needs oxygen what make that the cost of this concept to be more expensive than the concept using air. The economy of scale of the facility plays an important role in the energy production cost; it was found that facilities with a capacity fewer than 500 MW have a big influence between cost and the plant size. From facilities size of 1000 MW onwards, the influence decreases and does not shows and improvement on the production cost when the facility size is increased.