Biomass lignocellulosic

Wood is by far the most used and versatile lignocellulosic biomass and hence is in the main focus of this section. Other lignocellulosic biomass Uke grasses and Ugnocellulosic residues are compared to wood of minor importance but nevertheless shortly described. 

The main sources of wood are trees of natural and seminatural forests as well as forest plantations. 3.95 billion hectares of forests and forest plantations cover round about 30% of the land surface [26]. The largest forests are situated in Russia, Canada, Brazil, and the United States. Depending on the natural factors forests are either predominated by broadleaved trees or conifers. Broadleaved or hardwood trees belong to the taxonomic class of Angiospermae, while the conifers Pinoles) or softwood trees belong to the class of Gymnospermae. 

Wood The main compounds of wood are cellulose, hemicellulose, and lignin. Their share varies between hardwood and softwood as well as between single species. Table 4.4 shows the average shares of compounds in the cell wall of European hard- and softwood. Additionally, wood and bark contain a variety of extractives that are of interest for chemical and pharmaceutical applications. 

Due to the versatile physical and chemical characteristics applications of wood are numerous. However, the main uses for wood are heat and/or power generation 

The average growth of German forests is according to the second national forest inventory (BWT) 12.1 m per hectare and year. According to Mantau [28] in 2008 roundwood production in Germany amounted to 71.9 million m (see Table 4.5). 

---

Lignocellulose biomass is a mixture of phenolic lignin and carbohydrates -cellulose and hemi-cellulose. It grows abundantly on earth and is largely available as agricultural and forestry residues. Lignocellulose can be converted via four major routes pyrolysis, gasification, hydrolysis and fermentation. 

The present chapter discusses aspects, known by the authors, of (a) biomass as feedstock, (b) the concept of bio-refinery, (c) thermochemical routes from lignocellulosic biomass to fuels, and (d) the contribution of catalytic technology. The main focus will be on the catalytic conversion of fast pyrolysis oil into fuels with regard to problems encountered currently and the challenges for future research and development. 

Along with carbon, hydrogen and oxygen, lignocellulosic biomass also contains hetero elements such as alkali and other metals. The amounts of these ashes vary over a broad range, from 30-50 wt.% in chicken litter to 1-3 wt.% in wood. Moisture is always present in lignocellulosic biomass and can be up to 80 wt.% in some cases. Detailed information on the composition of biomasses can be found in data bases, e.g., Phyllis [21] from the Dutch Energy Research Foundation (ECN). Table 6.2 lists the compositions of some typical biomasses. 

NREL (National Renewable Energy Laboratory). Lignocellulosic biomass to ethanol process design and economics utilizing co-current dilute add prehydrolysis and enzymatic hydrolysis for com stover. Golden, CO US (2002). Report available on web http //www.mel.gov/ docs/ fy02osti/32438.pdf... 

Miranda, R. 2004. Hydrogen from lignocellulosic biomass via thermochemical processes. Energy Edu Sci Technol 13 21-30. 

Xylan is an essential constituent of hardwoods, softwoods, and annual plants. In enzymatic processing of lignocellulosic biomass, xylanolytic enzymes may be used either individually, in selected mixtures for specific effects on only the xylan component of the raw material, or in mixtures with cellulolytic, pectinolytic or amylolytic enzymes. 

Mosier N, Wyman C, Dale B, Elander R, Lee YY, Holtzapple M, Ladisch M. 2005. Features of promising technologies for pretreatment of lignocellulosic biomass. 

Gonzalez-Vila,F. J.,Tinoco, P., Almendros, G., and Martin,F. (2001). Pyrolysis-GC-MS analysis of the formation and degradation stages of charred residues from lignocellulosic biomass. I. Agric. Food Chem. 49,1128-1131. 

Lignocellulosic biomass is a valuable and plentiful feedstock commodity and its high cellulose and hemicellulose content (about 80% of total) provides considerable potential for inexpensive sugars production. However, enzymatic deconstruction of these polysaccharides remains a costly prospect. Strides in cellulase cost reduction have been made, yet further improvements are needed to reach the goal of 0.10/gal of EtOH expected to enable this new industry. Strategies to reach this goal will combine reduction in the cost to produce the needed enzymes as well as efforts to increase enzyme efficiency (specific activity). As this work proceeds, the more easily attained achievements will be made first, and thus the overall difficulty increases with time. 

Corn stover, a well-known example of lignocellulosic biomass, is a potential renewable feed for bioethanol production. Dilute sulfuric acid pretreatment removes hemicellulose and makes the cellulose more susceptible to bacterial digestion. The rheologic properties of corn stover pretreated in such a manner were studied. The Power Law parameters were sensitive to corn stover suspension concentration becoming more non-Newtonian with slope n, ranging from 0.92 to 0.05 between 5 and 30% solids. The Casson and the Power Law models described the experimental data with correlation coefficients ranging from 0.90 to 0.99 and 0.85 to 0.99, respectively. The yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of corn stover tested. 

Recent studies have proven ethanol to be an ideal liquid fuel for transportation and renewable lignocellulosic biomass to be an attractive feedstock for ethanol fuel production by fermentation (1,2). The major fermentable sugars from hydrolysis of lignocellulosic biomass, such as rice and wheat straw, sugarcane bagasse, corn stover, corn fiber, softwood, hardwood, and grasses, are D-glucose and D-xylose except that softwood... 

Cellulase Retention and Sugar Removal by Membrane Ultrafiltration During Lignocellulosic Biomass Hydrolysis... 

---