Pretreatment methods for the production of biofuels from lignocellulosic biomass

Public awareness on climate change, environmental problems and energy security is continuously growing and government cannot ignore the necessity to adopt urgent and sustainable (both economic and environmental) solutions to evolve our style of life. One of the solutions that is emerging is bio refinery: the conversion of biomass into valuable by-products, from bio-fuel to various chemicals. In a larger vision, it can be defined as a facility that optimizes the integrated production of heat, power, transportation fuels, materials, chemicals, feed and food from biomass. From the last few years, biorefinery is a promising sector with a considerable potential to capitalize the various lignocellulosic materials into a variety of relevant bio-products in industrial scale. Interestingly, a bio-refinery has an enormous potential to use and monetize all types of biomass-based sources that includes agricultural, agro-industrial, municipal, etc. Moreover, the materials produced by those sources are the most promising feedstock as they are a natural, abundant, and renewable resource essential to the functioning of industrial societies and critical to the development of a sustainable global economy. The field of biofuel energy has evolved considerably in the last few years. Innovations in the bio refinery world are providing a portfolio of sustainable and eco-compatibly products able to compete the market presently dominate by the petroleum-based products. Effort in the large scale translation of update technologies of conversion of biomass to biofuels have to be done in way to optimize the economy of conversions. There is no doubt that biofuels have the ability to fulfil the energy demand of the world, and also have the ability to reduce the carbon emissions, but accumulated bioenergy production on agricultural/cultivable land may rise a severe threats for the daily use of edible food crops. Thus, in recent years, kind of biomass considered as wastes have gained considerable importance owing to their novel characteristics that include renewability, recyclability and sustainability, words that are emphasized in growing scientific knowledge and environmental awareness. Lignocellulosic feedstock represents an extraordinarily large amount of renewable bio resource available in surplus on Earth and it is a suitable raw material for vast number of applications for human sustainability. Some of the major factors are the recalcitrance of the plant cell wall due to integral structural complexity of lignocellulosic fractions and strong hindrance from the inhibitors and by-products that are generated during pretreatment. This work is particularly focused on the pretreatment methods used to overcome these obstacles and to enhance the otherwise low effective conversion into valuable product. An overview of biomass, its distribution and uses is given, followed by a description of the building structure of lignocellulosic biomass. A panning on the available pretreatment methods used in these last years is given, and only the most common will be analysed in depth in the subsequent chapter. A proposal of optimization methods concludes this work, with some experimental results present in literature.