Forest-based biorefinery

One report stated that biorefinery-based fuel or chemical production is a strategy, framed to reduce GHG emissions. In practice, CO2 emissions produced by the biorefinery activities cannot be compensated for by the carbon fixation of plants, because a good majority of the plants are already exhausted through feedstock utilization. The situation exerted by biorefinery seems worse than petroleum-based biorefinery where at least there is a chance for CO2 to get sequestrated. This can be clearly visualized in Fig. 16.3. On the whole, it could be concluded that the forest-based biorefinery is not going to be feasible, as it converts all land-based carbon sources to CO2 and leaves no option for the emitted CO2 to get sequestrated (Delucchi, 2011). 

FIGURE 16.3 Incapability of forest-based biorefinery for carbon sequestration. 

Proposals to implement a biorefinery approach for platform chemical production have ignited a debate on whether biorefinery feedstock production threatens food security and increases the rate of deforestation (Ravindranath et al., 2008). It s worrying because the feedstock suitable for biorefinery implementation is procured primarily from forests. Any activity such as feedstock production, which puts considerable pressure on the forest cover, endangers natural heritage and biodiversity (Achten et al., 2013). This chapter discusses various forest-based feedstocks for biorefinery. Moreover, it seeks to elaborate the industrial applications of this feedstock, their characteristics and land requirements (essentially the extent of theoretical deforestation), their production, and procurement. Clearly the influence of biorefinery on woodlands will rely on the nature of the feedstock being used. For example, Brazil utilizes deforested land for sugarcane cultivation and subsequent ethanol production. However, in the case of Indonesia, rain forests were cleared for palm oil production. All of the biorefinery processes require cellulose as the raw material, and since the major source of cellulose in nature is in the form of trees, large-scale deforestation seems to be a plausible end scenario (Gao et al., 2011). 

This chapter is organized into three sections, apart from this introduction. The first section surveys in detail various feedstock that can be obtained from the forests and their lignocellulosic composition. Various classifications of forest-based feedstocks and their useful fermentation products are also discussed here. The second section presents the application of forest-based feedstocks in light of biorefinery and platform chemical production. To better understand the relationship between feedstock requirements and decreases in forest cover, a detailed analysis of land occupied by each forest-based feedstock will also be presented. The final section provides conclusions and suitable remedial measures to minimize deforestation due to biorefinery. 

TABLE 16.1 Composition of Representative Forest-Based Lignocellulosic Feedstock for Biorefinery... 

Conventionally, woody trees were broadly classified as softwood or gymnosperm and hardwood or angiosperm. Hardwood comes from angiosperms, such as oak, eucalyptus, and alder, which are dicots (Octave and Thomas, 2009). Softwood usually comes from evergreen conifer trees like pine or spruce. Other classifications of forest-based plants are broad-leaved trees and pine-leaved trees. Almost 46% of biorefinery prefers raw materials from conifer species, mainly spruce, pine, etc., and 31% of broad-leaves such as eucalyptus. Mostly stem wood is preferred as a suitable feedstock for the biorefinery process. Approximately 8% of the known biorefinery processes utilize all parts of the tree (Fitzpatrick et al., 2010). Thus the consensus in the biorefinery industry is that the feedstock selection should be based on the main constituents of the wood (cellulose, hemicellulose, and lignin) and not on specific chemicals (glucose, xylose, etc.) generally considered in conventional fermentation processes. 

FIGURE 16.1 The outline of a forest-based feedstock for biorefinery. 

The LUC further offers solutions to several issues like the feasibility of processes and the impact of the biorefinery on society. The impact of CO2 emissions due to the production of forest-based feedstocks can easily be calculated by adding the ongoing carbon emission to LUC and the production process (Delucchi, 2011). 

The platform chemicals described earlier mainly rely on feedstock, for instance, 70% of the total cost of the fermentation product is based on feedstock. Hence substrate costs are the most influential parameters in platform chemical production from renewable resources. The cost of the substrate is not only based on pretreatment and fractionation but also on the severe environmental damage caused by deforestation for feedstock requirements (Octave and Thomas, 2009). As mentioned earlier, to get a few hxmdred kilograms of chemicals, a huge ton of forest biomass is consumed. Hence the biorefinery sector should divert its focus from wood to forest wastes, paper mill wastes, agricultural residues, and other municipal wastes. This will decrease the pressure on forest biomass and make the entire process sustainable. In order to reduce deforestation, a few strategies are to be followed in biorefineries ... 

Because of the high demand of biofuels in the present situation, several biorefineries have been established based on the availability of agriculture and forest products and also in efforts to utilize wastes obtainable from the paper and pulp industry, sugar mills, etc. (Cherubini et al., 2009). This system yields transportation fuels such as biodiesel and bioethanol, platform chemicals, and some chemical intermediates for cosmetics and pharmaceuticals. Since the Phase III biorefineries are the ones that may be expected to serve as an all-in-one source of food, feed, and platform chemicals, the various known forms of Phase 111 biorefineries are discussed in some detail below. 

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