The cost disadvantages of bioenergy conversion from lignocellulose relative to fossil-based energy sources can be addressed through innovative methods of process integration, the goal of which is to minimize capital investment, maximize energy efficiency and thus improve overall economics. Such optimisation of overall process performance and energy efficiency will also increase the environmental benefits that can be derived from bioenergy production. Heat integration within biochem­ical and thermochemical routes of lignocellulose conversion has the potential to increase overall energy efficiency by as much as 15 % and can reduce capital and operational costs substantially (Van Zyl et al. 2011; van der Drift et al. 2004). Similarly, the integration of energy cycles for biomass conversion processes with adjacent/associated industrial processes can address both energy efficiency and production costs of the lignocellulose conversion process. Process integration with adjacent industrial processes can be broadly classified as (i) integration with electricity production from biomass or fossil fuels, (ii) integration with biomass processing for pulp or sugar production, (iii) integration of first and second — generation biofuel production by biochemical processing, (iv) integration of second — generation biofuel production by thermochemical processing with petrochemical processing and (v) integration of biochemical and thermochemical processing of lignocellulose to second-generation biofuels. The economics of process integration carries scale-dependent economic benefits, whereby more expensive, high efficiency equipment becomes affordable at larger production scales. Several of the conversion technologies presented in this chapter may be combined to form a value chain, in particular through the production of bioenergy intermediates such as wood chips, pellets and briquettes and liquid products such as bio-oil. These intermediates have higher bulk density than harvested lignocellulose which significantly reduces biomass feedstock transportation costs (Stephen et al. 2010; see Chap. 6). Further examples of integration of more than one conversion technology are presented below.

Combustion and gasification: Gasification combined with pre-combustion carbon capture can be used to produce either biofuels or electricity and improve the efficiency of Integrated Gasification Combined Cycle processes (IGCC) (Prins et al. 2012). Pre-treating biomass with hydrothermal carbonization (HTC) produces a coal-like substance (biocoal) which is potentially better suited for entrained flow gasification than raw biomass (Erlach et al. 2012).

Gasification and combustion: Biomass downdraft reactors coupled with recipro­cating internal combustion engines (RICEs) are a viable technology for small scale heat and power generation (Martinez et al. 2012). Dry gasification oxy-combustion (DGOC) is a process best described as a hybrid between gasification and oxy — combustion systems (Walker et al. 2011).

Torrefaction and gasification: The main idea behind combining biomass tor — refaction and gasification is that the heat produced during gasification in the form of steam is recovered for application to torrefaction (Van der Stelt et al. 2011;

Prins et al. 2006). Gasification using torrefied biomass allows for improved flow properties of the feedstock, increases levels of H2 and CO in the resulting syngas and improves overall process efficiencies.

Torrefaction and combustion: Combustion reactivity of torrefied biomass has been evaluated and shows promise for biomass co-firing in existing coal-fired power stations (Bergman et al. 2005; Bridgeman et al. 2008).

Torrefaction and fast-pyrolysis: Recent development of torrefaction as a pretreat­ment technology for fast pyrolysis results in enhancement of bio-oil properties by reducing oxygen-to-carbon ratios and water content (Meng et al. 2012).

Fast-pyrolysis and gasification: The adaptation of distributed fast pyrolysis biomass processing systems to central gasification systems in order to facilitate the production of hydrocarbon transport fuels is currently being developed by KIT (Dahmen et al. 2012). Fast pyrolysis bio-oil can also be gasified through a catalytic steam reformer (Czernik et al. 2002). Bio-oil gasification in entrained flow, oxygen blown pressurised gasifier systems is also feasible with applications currently in use by Texaco and Shell (Bridgwater 2011).

Fast-pyrolysis and combustion: The integration of fast pyrolysis and combustion technologies have been extensively studied (Czernik and Bridgwater 2004) and commercially applied (VTT, Dynamotive, Ensyn, btg-btl), while also being under further development (Khodier et al. 2009).

Direct liquefaction and gasification: Pre-treating biomass with hydrothermal car­bonization (HTC) produces biocoal which is potentially better suited for entrained flow gasification than raw biomass (Erlach et al. 2012).