Bioethanol lignocellulosic conversion

Watanabe, T. Potential of cellulosic ethanol. In Lignocellulose conversion Enzymatic and microbial tools for bioethanol production, Faraco, V, Ed., Springer Verlag Berlin, 2013, pp. 1-20. 

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],... 

Biochemical refinery conversion of lignocellulosic biomass by fermentation to bioethanol and chemicals. 

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. 

The conversion of lignocellulosic biomass to bioethanol is, however, a challenging one as the raw material consists of complex polymers, namely... 

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. ... 

Life cycle assessment (LCA) has been suggested as a suitable methodology to assess the environmental impact of 2G bioethanol production in order to identify the most appropriate conversion technologies and lignocellulosic feedstock. Numerous studies can be found in the literamre that focused on the environmental... 

Figure 4.3 illustrates different possible conversion routes for the production of ethylene from biomass. One way to produce ethylene from renewable feedstock is catalytic dehydration of bioethanol. In the short term, it is likely that bioethanol dehydration for the production of ethylene will be established in regions with cheap access to bioethanol, for example, Brazil, where ethanol usage is on the same level as usage of fossil-based fuels (on an energy basis) in the transportation sector. In Europe and the United States, this trend is expected to occur after the commercial introduction of lignocellulosic ethanol (Jones et al., 2010). 

Bioethanol is produced from the hydrolysate of lignocellulosic substrate after pretreatment and enzymatic hydrolysis. With high conversion of carbohydrates, hexose and pentose can be fermented by commercial or engineered Saccharomyces cerevisiae or other microorganisms. Depending on the feedstock and pretreatment processes, various types of growth-inhibiting compounds have been discovered to hinder the performance of fermentation. For example, HMF and furfural formed from dehydration of... 

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