Second Generation Bioethanol from Lignocellulosics: Processing of Hardwood Sulphite Spent Liquor

The world is facing a reduction of global fossil fuels resources, like petroleum, natural gas, or charcoal, while energy requirements are progressively growing up. Fossil fuels should be replaced, at least partially, by biofuels once the current fuel supply is suspected to be unsustainable in the foreseen future. In fact, the search for sustainable alternatives to produce fuel and chemicals from non-fossil feedstocks has attracted considerable interest around the world, to face the needs of energy supply and to response to climate change issues. Alternative resources of energy are being explored in order to reduce oil dependence and increase energy production by exploring of solar, wind, hydraulic and other natural phenomena. Besides these sources of energy, also biomass possesses a potential target for fuel and power production as well as for chemicals or materials feedstocks. Thus biomass can efficiently replace petroleum-based fuels for a long term. (Sanchez et al. 2008; AlvaradoMorales et al. 2009; Brehmer et al. 2009; Gonzalez-Garcia et al. 2009; Singhania et al. 2009; Mussatto et al. 2010; Sannigrahi et al. 2010). Many countries in Europe, North and South America and Asia are replacing fossil fuels by biomass-based fuels according to international regulations. One of the directives of European Union (2009/28/CE) imposes a quota of 10% for biofuels on all traffic fuel until 2020 (Rutz et al. 2008; Xavier et al. 2010). Also economic incentives for research on biofuels are being implemented all over the world. Bioethanol can be produced from different raw materials containing simple sugars, starch or more complex substrates as lignocellulosics. New methodologies for biofuels (e.g. ethanol and biodiesel) production have been developed in the last years, to achieve new and non cost-intensive technologies for bioconversion of lignocellulosic renewable resources. The most common renewable fuel is ethanol, which is produced from direct fermentation of sugars (e.g. from sucrose of sugarcane or sugar beet) or polysaccharides (e.g. starch from corn and wheat grains) (Gonzalez-Garcia et al. 2009; Mussatto et al. 2010). The selection of the best raw material is strongly dependent on the local conditions where feedstock is obtained. Evidently, ethanol in Brazil is produced from sugarcane, whereas, in North America or Europe the ethanol industry is based on starchy materials. Besides, energy considerations should be attained: not only the energy input required for ethanol production and the content in fermentable