Lignocellulose ethanol production process

Table 4.1 Main results of process simulation of the lignocellulosic ethanol production process...

A unique pilot plant for ethanol production from lignocellulose feedstock was inaugurated in O-vik, Sweden in May 2004. The aim of the pilot plant was to develop efficient continuous technologies for the various process steps in ethanol production from forest raw material and other lignocellulosic feedstock. Different raw materials require different conditions during the production process and the process also needs to be optimised for every raw material. Further it was important to demonstrate that large-scale lignocellulose ethanol production was possible... 

In cellulosic ethanol production processes, a pretreatment procedure is needed to disrupt the recalcitrant structure of the lignocellulosic materials so that the cellulose can be more efficiently hydrolyzed by cellulase enzymes [2], These pretreatments include physical, biological, and chemical ways, such as uncatalyzed steam explosion, liquid hot water, dilute acid, flow-through acid pretreatment, lime, ammonium fiber/freeze explosion, and ammonium recycle percolation [3, 4], Most of these methods involve a high temperature requirement, which is usually achieved through convection- or conduction-based heating. 

In direct microbial conversion of lignocellulosic biomass into ethanol that could simplify the ethanol production process from these materials and reduce ethanol production costs, Clostridium thermocellum, a thermoanaerobe was used for enzyme production, hydrolysis and glucose fermentation (755). Cofermentation with C thermosaccharolyticum simultaneously converted the hemicellulosic sugars to ethanol. However, the formations of by-products such as acetic acid and low ethanol tolerance are some drawbacks of the process. Neurospora crassa produces extracellular cellulase and xylanase and has the ability to ferment cellulose to ethanol 139). 

Galbe M, Zacchi G. (1992). Simulation of ethanol production processes based on enzymatic hydrolysis of lignocellulosic materials using ASPEN PLUS. Appl Biochem Biotechnol, 34, 93-104. 

Figure 5.1 Ethanol production process from (a) starch and (b) lignocellulose.

Figure 5.4 Process flows for lignocellulosic ethanol production via (a) simultaneous saccharification and fermentation and (b) consolidated bioprocessing.

Chiaramonti, D., Prussi, M., Ferrero, S., Oriani, L. et al. (2012) Review of pretreatment processes for lignocellulosic ethanol production, and development of an iimovative method. Biomass Bioenergy, 46, 25-35. 

Paulova, L., Kacaba, J., Patakova, P., Rychtera, M. et al. (2012) Degradation products formed in physicochemical pretreatment of lignocellulose biomass and their influence on the effectivity of the ethanol production process. Chem. Listy, 106, 626—631. 

Figure 4.7 CCC of the ethanol production process from lignocellulosic biomaiss direct stream injection of 51 MW in the pretreatment steps is considered a process requirement and therefore not included...

Zaldivar, J., Nielsen, J., and Olsson, L. Fuel ethanol production from lignocellulose a challenge for metabolic engineering and process integration. Appl. Microbiol. Biotechnol. 56 17-34 (2001). 

Many factors influence the reactivity and digestibility of the cellulose fractions of lignocellulose materials. These factors include Hgnin and hemicellulose content, crystalhnity of cellulose, and the porosity of the biomass materials. Pretreatment of Hgnocellulosic materials prior to utiHzation is a necessary element in biomass-to-ethanol conversion processes. The objective of the pretreatment is to render biomass materials more accessible to either chemical or enzymatic hydrolysis for efficient product generation. The goals of the pretreatment are ... 

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. 

Both Tween 20 and 80 are non-toxic and suitable for food and/or biofechnical use, such as stimulants for enzyme production by microorganisms [29-31] and additives in the SSF process for ethanol production [2]. BSA was used to improve the enzymatic conversion of lignocellulosic biomass because of its high affmity to lignin but little affinity to cellulose [17]. 

Initial commercial application of thermophilic ethanol production via CBP is most likely and most economically advantageous as a bolt-on to an existing ethanol mill - for example, processing corn, sugar cane, or lignocellulose. Such application would be a significant milestone for thermophiles and use of nonstandard host microbes, and appears to be a possibility in the near future. 

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