Bioethanol lignocellulose processing

In summary, currently there is no method that could meet all the requirements for the pre-treatment of lignocellulosic raw materials. Table 6.2 compares the advantages and disadvantages of various methods that are commonly used in the advanced generation bioethanol production process. 

As cellulose only represents 30-40% of the lignocellulosic biomass, the utilization of only glueose in the fermentation would undeniably have an effect on the overall biomass to ethanol conversion yield. Therefore, it is necessary to eonsider the utilization of the hemicellulose hydrolysate in the development of the advanced generation bioethanol production process. ... 

Biocatalytic conversion of lignocellulose into bioethanol, which requires upgrading of existing processes of fermenting sugars by using enzymatic-enhanced pretreatment of (hemi)cellulose. New, improved biocatalysts are needed for this route. 

Combinations of 1st and 2 nd generation conversion routes and technological coupling of biofuel and electricity conversion ( hybrids ) are potential options in the near future. For example, the process efficiency for a combined cycle (CC) is typically around 50% and could be improved to about 58% using a combination of BtL and CC or to around 70% using bioethanol produced from lignocellulose combined with BtL and CC [2],... 

Xylose is the major sugar present in the hemicellulose fraction of agricultural residues, such as wheat straw. Because the raw material cost is greater than one-third of the overall ethanol production cost [5], fermentation of xylose together with glucose is needed to improve the economics of any lignocellulosic-based bioethanol process. 

Gurrently, bioethanol is the main product produced from lignocellulosic feedstock. The process of bioethanol production from lignocellulose is currently tested in pilot plants in different countries all over the world, and according to Tan et al. [23] it is consisting of the following steps as discussed next (see Figure 5.6). 

US 0.29/L and US 0.53/L, respectively (Balat, 2011). In 2011, NREL (Colorado, USA) published the detailed report Process Design and Economics for Biochemical Conversion of Lignocellulosic Biomass to Ethanol (Humbird et al.. Mar. 2011). The NREL process design converts corn stover to ethanol by dilute-acid pretreatment, enzymatic saccharification, and co-fermentation, and with a minimum ethanol selling price (MESP) of US 2.15/gal (US 0.57/L calculated) by 2012 conversion targets (Table 7.3). In the report, the biomass amount processed is 2205 dry ton/day at 76% theoretical ethanol yield (79 gal/dry ton). It is expected that this MESP will become the standard for the cost of cellulosic bioethanol. 

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