ABSTRACT
Nowadays about 85 million barrels of crude are processed and used to meet the energy needs of the world. The demands for crude oil are projected to increase to 116 million barrels by 2030 [2]. Since this may result in depletion of crude oil reserves in the world, it is imperative to consider energy sources alternative to crude oil [3]. So the worldwide interest in biofuels and biochemicals produced using nonedible feedstock such as lignocellulosic biomass is growing. The biomass conversion technology choice, together with feedstock supply chain development, plays a key role in the commercialization of next-generation biofuels. In fact the production of second-generation biofuels is even more challenging than producing first-generation ones due the complexity of the biomass and issues related to producing, harvesting/picking up, and transporting less dense biomass to centralized biorefineries. In addition to this logistic issue, other challenges with respect to processing steps in converting biomass to liquid transportation fuel, like pretreatment, hydrolysis, fermentation, and fuel separation, still exist and are discussed in this chapter. The conversion technologies for biobased materials to advanced biofuels can be broadly classified into two major categories, biochemical and thermochemical conversions. Biochemical conversion describes the transformation of biomass by microorganisms or enzymes into simple sugars and intermediates. Thermochemical conversion describes the thermal breakage of biomass obtained through the use of heat in the biomass and includes torrefaction, pyrolysis, liquefaction, combustion, and gasification [4]. Both technologies are not a ‘‘one size fits all’’; many possible configurations exist for each conversion approach. In biochemical conversion there are a multitude of pretreatment approaches, as well as fermentation approaches. In thermochemical conversion there are a multitude of gasification, as well as fuel synthesis options, in addition to multiple pyrolysis to fuels options. The thermochemical biomass conversion process is complex and uses components, configurations, and operating conditions which are more typical of petroleum refining. The biochemical way, if the process is well designed, has the potential to be scalable, controllable, and economically sustainable. It is in fact important that all the unit operations integrate into an efficient overall conversion process. Whereas performance targets
for individual unit operations are defined as levels of conversion at specific conditions, overall integration targets are defined as overall cost, both capital and operating, efficiency, and availability. Ideally, the overall conversion process should be as simple as possible and robust, providing maximum availability. For any sophisticated conversion process, combining individual unit operations into a complete, integrated, efficient process is a significant challenge. The integration challenge is to design and validate a conversion process which affords maximum efficiencies and operational robustness. The objective of the present chapter is to illustrate the state-of-art of biochemical conversion technologies which are potentially ready or are already being deployed for large-scale applications, presenting also the process design, integration, and scale-up. 19.2 Thermochemical and Biochemical ProcessesThe production of liquid and gaseous fuels from lignocellulosic feedstock can be performed both through thermochemical and through biochemical conversion approaches (Fig. 19.2).
