ABSTRACT
Fossil fuels are the primary source of energy, chemicals and materials for our modern society. Petroleum, natural gas and coal supply most of the energy consumed worldwide and their massive utilization has allowed our society to reach high levels of development in the past century. However, these natural resources are highly contaminant, unevenly distributed around the world and they are in diminishing supply. These important concerns have stimulated the search for new well-distributed and non-contaminant renewable sources of energy such as solar, wind, hydroelectric power, geothermal activity, and biomass. This shift toward a renewable-based economy is currently spurred by governments which have established ambitious targets to replace an important fraction of fossil fuels with renewable sources within next 20 years [1] and [2]. In this sense, biomass is considered the only sustainable source of organic carbon currently available on earth and, consequently, it is the ideal substitute for
petroleum in the production of fuels, chemicals and carbon-based materials [3].
