Fractionation of lignocellulosic feedstock

2.2. Definition

Conversion of lignocellulosic materials to higher value products requires fractionation of the material into its components: lignin, cellulose, and hemicellulose, which convert to fuels, and chemicals for the production of most of our synthetic plastics, fibres, and rubbers is technically feasible. Liquefaction of LCF might serve as feedstocks for cracking to chemicals in the similar way that crude oil is presently used. Currently commercial products of LCF fractionation include levulinic acid, xylitol, and alcohols [104]. The ultimate goal of LCF fractionation is the efficient conversion of lignocellulose materials into multiple streams that contain value-added compounds in concentrations that make purification, utilization, and/or recovery economically feasible [15].

Fractionation of LCF is being developed as a means to improve the overall biomass utilization. Hemicellulose when separated from the LCF may find broader use for chemicals, fuel, and food application. The lignin separated in the process can be used as a fuel [105]. Unlike the lignin generated from pulping process, lignin fractionated from biomass by our approach is relatively clean, free of sulphur or sodium.

Fractionation of lignocellulosic materials is very difficult to accomplish efficiently, because of their complex composition and structure [106, 107]. However, fractionation of lignocellulosic materials is essential for some important applications, for example, paper­making, and in their conversion into basic chemical feedstocks or liquid fuels.

> iottch./ch*m (cal’

high value-added products [108]. Achieving high fractionation yields and maintaining the integrity of the macromolecular fractionation products are of major importance regarding the effectiveness of the whole refining process [109].

Figure 8. Lignocellulosic Feedstock Biorefinery [110]

Further research on the distilled fractions

Based on the molecular distillation results, a scheme of the process combining molecular distillation separation with bio-oil upgrading is proposed. The light fraction rich in carboxylic acids and other light components could be used for esterification, catalytic cracking, and steam reforming, to produce ester fuel, hydrocarbons, and hydrogen, respectively. For the middle fraction, steam reforming at high temperature or hydrodeoxygenation at high pressure could efficiently convert this fraction into hydrogen or hydrocarbons. The heavy fraction, which consisted mainly of pyrolytic lignin and sugar oligomers, could be emulsified with diesel to obtain emulsion fuel with a relatively high heating value. On the other hand, the extraction of some valuable chemicals can benefit the overall economy of this process.

Recently, some further research has been performed, aiming at investigating some characteristics of the distilled fractions and devising more promising upgrading methods. Thermal decomposition processes and the pyrolysis products of crude bio-oil and distilled fractions were investigated by means of TG-FTIR by Guo (Guo et al., 2010a). The light

fraction (LF) was completely evaporated at 30-150 °C, with the maximum weight loss rate at about 100 °C due to the volatilization of water and compounds of lower boiling point. The middle fraction (MF) and heavy fraction (HF) contained more lignin-derived compounds, and these decomposed continuously over a wide temperature range of 30-600 °C, leaving a final residue yield of 25-30%. Upgrading of the distilled fraction rich in carboxylic acids and ketones was carried out by Guo (Guo et al., 2011). Carboxylic acids accounted for 18.39% of the initial fraction, with acetic acid being the most abundant. After upgrading, the carboxylic acid content decreased to 2.70%, with a conversion yield of 85.3%. The content of esters in the upgraded fraction increased dramatically from 0.72% to 31.1%. The conversion of corrosive carboxylic acids into neutral esters reduced the corrosivity of the bio-oil fraction.

Figure 6. A scheme of the process combining molecular distillation separation with bio-oil upgrading.

Author details

Shurong Wang Zhejiang University, China


The author acknowledges the financial support from the Program for New Century Excellent Talents in University, the International Science & Technology Cooperation Program of China (2009DFA61050), Zhejiang Provincial Natural Science Foundation of China (R1110089), the Research Fund for the Doctoral Program of Higher Education of

China (20090101110034), the National Natural Science Foundation of China (50676085) and

the National High Technology Research and Development Program of China

(2009AA05Z407). The author also highly appreciates the kind support from Mr. Zuogang

Guo, Mr. Qinjie Cai, Mr. Long Guo and Miss Yurong Wang, who have been involved in the

experimental research and the preparation of this chapter.

Studies of biosorption of heavy metals with aerobic bacteria using biomass support in batch system

For studies of biosorption of heavy metals using aerobic bacteria and a support for the biomass, using 500 mL Erlenmeyer flasks, which are placed 5 g of the support for the immobilization of selected biomass, 90 mL of a solution containing the metal study established at an initial concentration, 10 ml of biomass with a density of 1 g/L and as target, 100 mL of metal with 5 g of support material. The flasks were plugged with a cotton swab having aeration, then is placed in an incubator with shaking at 100 rpm and temperature established for mesophilic bacteria to 45 °C. Samples are taken at set times to analyze the concentration of metals by atomic absorption. The conditions are the same for the studies using only bacteria without carrier material. All experiments were performed in duplicate and the efficiency of biosorption (E) is calculated using the equation:

E = ( C° — Cf ) *100 (23)


Where: Co y Cf initial and final amounts of the metal (mg/L).

The logistic curve approach

According to Graham (1939), the maximum yield that can be extracted from a wild stock is found at the half of the virgin size of that population, as seen in Fig. 1A, B. A similar view is commented by Zabel et al. (2003). After this premise, a simplistic approach can be adopted by assuming that when the catch trend shows a maximum, followed by a decline, then that

Figure 1. Principles of the logistic growth of a population (A) and the surplus yield of an exploited stock (B). Horizontal scale of Fig. A is time and in Fig. B indicates population size.

maximum yield corresponds to the half of the population size at the virgin stock. Stock assessment based upon this approach is very limited and despite that its ecological principles as background are valid, there are many factors constraining the validity of this procedure and therefore other approaches more accurate and based upon age structure have been adopted over time.

By following the former statements, a simple approach to roughly estimate the stock biomass is by just fitting a parabola to the catch records of some fisheries or regions, even deliberately ignoring a relationship of the stock density of populations, just by usually using the catch per unit of effort as an indicator of stock density. In this case, time was used as an indirect indicator of fishing effort, because the information on this variable is not easily available and because it is beyond the scope of this paper. Therefore, second degree regressions were used to several fisheries and regions just to have an idea on when the maximum yields, presumably equivalent to the Maximum Sustainable Yields (MSY), were attained. It is assumed that the stock biomass is at least twice bigger than the maximum yield attained in a certain time, and in that point is supposed that the exploitation rate E, is 50 per cent. This approach is conservative, because the intrinsic growth rate is not provided, given that many populations are involved. In the stock assessment process, the E value is usually lower than 0.5; however, by considering that many species are involved in the procedure is analysis, is likely to expect that in this collection there may be species which are overexploited, as well as others which may be underexploited. For this reason, it is reasonable to adopt a conservative criterion instead of being too optimistic assuming that the biomass could reach higher values. It is pertinent to mention that most of the regressions applied and described in the following paragraphs excepting three, provided high and significant R2 coefficients.

On being consistent with this idea, estimations of the MSY by applying a parabola were fitted to catch data of the world fisheries exploited and recorded for different regions as shown in Fig. 2 (A — F) and in Table 1. The time scale of catch extracted from FAO (2010), data goes from 1950 to 2010. It is evident that in most cases the catch has attained a maximum yield, which for practical purposes; it can be considered as equivalent to the MSY level.

Cluster analysis of energy indices and balance energy indices for rice production

In cluster analysis genotypes were classified into four groups based on Ward’s method. Cluster analysis showed that Hybrid and Gohar varieties and Alikazemi, Khazar and Hashemi varieties in group similarities "Figure 9".


Distance Cluster




0 5

10 15 20





-+———— +—-

—- +——


—- +



— + — +



-+ +—

—- +








—- +




Figure 9. Dendrogram of rice genotypes based on different ward method

3.2. Yield function

Relation between amounts of energy efficiency (energy output to input energy ratio) and energy balance efficiency (production energy to consumption energy ratio) and their effect on paddy yield, straw yield, husk yield and biomass yield were showed in figure 10. Paddy yield, straw yield, husk yield and biomass yield were increased with of use energy efficiency and energy balance efficiency "Figure 10". Yield function of paddy yield, straw yield, husk yield and biomass yield obtained by following relationship "Figure 10".

Availability of residual biomass in Ecuador

Ecuador is a biodiverse country with rich and fertile natural regions. In the coastal zone of Ecuador there is the large scale agriculture of a wide variety of crops which have positioned this country as one of the most important producers of bananas, palmito (palm heart), oil palm and other valuable products in South America. Moreover, Ecuador has unique vegetal species that are being exploited in small scale, presenting novel and potential sources of lignocellulose for the future.

In terms of abundance of lignocellulosic residues, the most conspicuous industries producing leftovers—as a consequence of the harvest or the extraction of valuable commodities—are the bananas farms, and the oil palm and sugar cane mills. There are still other important industries located mainly in the highlands such as flowers and cereals that produce lignocellulosic material potentially usable. Nevertheless, the amounts of these residues are not enough for huge biorefining installations, nor even available in an economical and technical way.

As for the availability of residues, studies carried out by researchers from the Neotropical Center for the Biomass Research at the Pontificia Universidad Catolica del Ecuador, reveal that there is a very high potential for lignocellulosic ethanol and biorefineries setting up in Ecuador. Nevertheless, there still exist constraints due to the disperse areas where the agricultural and industrial lignocellulosic materials are disposed; the local roads infrastructure and networks; the lack of development of markets for certain specific residues; the traditional uses and ways of final disposal; the physical and chemical composition of residues; and, the prices per dry ton. There are also social and environmental components to be taken into account when projecting lignocellulosic biorefineries to take the most of the agricultural and industrial byproducts, leftovers or residual material. In our survey we have considered the above-mentioned factors to develop the feasibility study for a biorefinery based on local lignocellulosic residues in the country.

In this survey we have pursued the following general objectives:

1. Evaluate the abundance and the potential of the main crops produced in Ecuador.

2. Determine the utilization, destiny, and availability of the agricultural residues.

3. Estimate the evolution of the agricultural production and residues generation in 5 years (until 2014).

Moreover, we have focused the following specific goals:

1. Determine the main crops in Ecuador, its exact geographical location, and the quantity of biomass residues produced per year.

2. Establish the temporality of crops and harvest.

3. Take current and historical data on volume of waste biomass produced to project future volumes, considering a period of five years. Analyze the succession of crops

4. Determine on the basis of the previous information, the more adequate zones where to install a future biorefinery plant.

In Ecuador there are three crops that worth to be studied with biorefining ends, because of their characteristics in terms of composition, final disposal, abundance and lack of sustainable use. These crops are: bananas, sugar cane and oil palm.

Table 3 shows the complete results of our survey on 13 different crops in Ecuador, the calculation of its dry mass and cellulose average contents as well as the potential for ethanol production. As it is going to be seen, Ecuador potentially could provide at least half of the ethanol needs for replacing gasoline in vehicles if the cellulose contained in agricultural residues were transformed into ethanol.

This suggests that biorefinery plants can be a reasonable and sustainable option for the post oil economy in Ecuador. Moreover, there still exists a huge potential for power generation if biogas from stills and residual lignin are burned in biorefineries.

There still exist other valuable products from biorefining of second generation ethanol such that can be produced from the residual water generated after distillation which, after an anaerobic digestion process, yields biogas, liquid and solid fertilizers (sludge). The non — hydrolyzed fibers as well as yeast biomass obtained after fermentation can be dried and sold as animal feed solid matter. The solid matter that can be recovered from fermenters before distillation is really considerable. Moreover, carbon dioxide from fermentation can be collected and treated to be sold in as much as during the fermentation for ethanol production, almost the same amount of CO2 is released. Theoretically, the production ratio of ethanol to CO2 in fermentation is 92:88. The uses for this gas are very wide including food, drink and chemical industries. CO2 is widely used in soft drinks and beer to carbonation of these beverages. It is also used to fill packs of vegetables and meet to keep it fresh. CO2 can also be used as raw material for the synthesis of methanol, formic acid, and urea. Other applications of CO2 include its use as a medium in supercritical CO2 extraction and in fire extinguishing equipment [4].



Residues by Product

Dry weight (MT/year)

Average cellulose content (IVIT/year)

Theoretical potential ethanol (Gal)




Percent of potentially supplied vehicles per year (Total number of cars: 1.4 MM to 2014)

Soy bean




































Soft corn
























Dry corn












Oil palm












Table 3. The hypothetical potential of lignocellulosic biomass in Ecuador to produce cellulosic ethanol

New algorithm to predict potential biomethane yield

As it was commented above biomethane yield in terms of total slurry mass (BMPTM) significantly correlated with DM concentrations. We tested the possibility of predicting BMPTM using the concentration of DM, VS and the concentration of lignin and VFA, which were a significant variable for BMP. The results of the regression tests are shown in Table 5, where quite high correlations were found for all the models. However, critical relative errors using DM as an independent variable were found, that is, 62.1 %, which seems to be because the wide range of DM improved the correlation level. Hence, when assessing BMPTM, only TS can be used when further characterisation is not possible. Apart from DM, relative errors were much lower when using VS and VS together with lignin and VFA, indicating a good potential of applying the model for prediction.






DM ( g kg -1)




BMPtm = -0.934+0.201*DM

VS (g kg-1)




BMPtm = 0.610+0.229*VS

VS ( g kg -1) Hgnm (% of VS ) and VFA (% of VS)




BMPtm = 4.654+ 0.230*VS +0.009*VFA -0.360*lignin

Table 5. Summary statistics results, algorithm obtained for BMPtm.

5. Conclusion

The study highlights the critical quality of VS in cow manure and the critical quantity of VS in pig slurry which results in low viability of biogas production using animal slurry. The very high concentration of lignin in cattle and dairy cow manure indicates that there is a need of pretreatment either to reduce the influence of lignin by releasing lignocellosic bindings, or by depolymerizing lignin polymer. Whereas low digestibility of cow manure is problematic due to high concentration of lignin, lignin concentration of pig and mink slurry was relatively low. However despite of preferable digestibility of pig and mink slurry, the large amount of water and very low VS concentration in them indicates that there is a need of a qualified control of water content during management. Our study shows that control of DM concentration is more crucial than control of BD of substrate to enhance methane yield. Hence, the study highlights the importance of a qualified control of water content in feedstock by co-digesting solid organic substrates that can enrich VS concentrations prior to improvement of substrate digestibility by pretreatment.

Author details

Jin M. Triolo[2], Lene Pedersen and Sven G. Sommer

University of Southern Denmark, Faculty of Engineering, Institute of Chemical Engineering,

Biotechnology and Environmental Technology, Odense M, Denmark

Alastair J. Ward

Aarhus University, Dept. of Biosystems Engineering, AU Foulum, Tjele, Denmark

Biopulping and wood utilization

Biopulping, also known as biological pulping, refers a type of industrial biotechnology using fungus to convert wood chips to paper pulp. This technology has the potential to improve the quality of paper pulp, reduce energy consumption and environmental impacts when compare with the traditional chemical pulping technologies [189].

The aim of pulping is to extract cellulose from plant material. The traditional approaches are mechanical and chemical pulping. The former method is generally accomplished by refining grinding or thermo-mechanical pulping. The latter way is to dissolve lignin from the cellulose and hemicellulose fibers via chemical treatment, such as kraft pulping in which wood chips are cooled in a solution containing sodium hydroxide and sodium sulfide [190]. These traditional pulping technologies have several drawbacks: (1) high energy demand; (2) low cellulose yield, especially from chemical pulping due to partial degradation of cellulose;

(3) potential hazards chemicals emitted to the environment [189].

Lignin is a complex polymer which serves as a structural component of higher plants and is highly resistant towards chemical degradation [191]. White-rot and brown-rot fungi are two classifications of wood-rotting basidiomycetes. White-rot basidimycetes have been reported enable to, selectively or simultaneously with cellulose, degrade lignin in different types of wood [191, 192]. Brown-rot basidiomycetes, which grow mainly on softwood, can degrade wood polysaccharides but cause only a partial modification of lignin. Besides white — and brown — rot basidimycetes, some scomycetes so-called soft-rot fungi which can degrade wood under extreme environmental conditions such as high or low water potential that prohibit the activity of other fungi [191].

The fungal treatment process fits in a paper mill operation well. After wood is debarked, chipped and screened, wood chips are briefly steamed to reduce natural chip microorganisms, cooled with air, and inoculated with the biopulping fungus for 1 to 4 weeks prior to further processing. The biopulping has been indicated as a technology technologically feasible and economically beneficial [193].

This biological treatment of wood using fungi has also been studied and used as a pre­treatment approach prior to enzymatic hydrolysis for biofuel production [194-196]. However, more research are required to understand the mechanism of wood degradation, structural changes of wood cell wall caused by these wood decay fungus and to improve the treatment technologies [197, 198].

6. Conclusions

The concept of ‘biorefinery’ has emerged since the potential of lignocellulosic based products substituting fossil fuel derived products has been discovered. Biorefienries may play a major role in tackling climate change by reducing the demand on fossil fuel energy and providing sustainable energy, chemicals and materials, potentially aiding energy security, and creating opportunities and market. This paper reviewed a wide range of such lignocellulosic derived products and current available biorefinery technologies. Some of these technologies have been or being close to the industrialization and others are still at the early stage of development. However, more research efforts are required to improve the technologies and integrate the biorefinery system in order to achieve the maximum outputs and to make biorefinery work at scale.

Author details

Hongbin Cheng [3] +

Department of Process Engineering, Stellenbosch University, Stellenbosch, South Africa New China Times Technology Ltd, China

Lei Wang+

Department of Life Science, Imperial College London, London, UK New China Times Technology Ltd, China

Perspectives for future research: The use of willows in phytoremediation

In Canada, it is estimated that millions of hectares of arable land lie uncultivated. These so — called marginal lands tend to be less productive, less accessible, poorly drained, or even contaminated [79]. Willows have been successfully used to capture leached nutrient and heavy metals from soils [54, 59, 80, 81]. The various species of Salix have been shown to establish well on these marginal and contaminated soils, which provides new research opportunities for future applications.

3.1. Phytoremediation

The main types of contaminants found in Quebec soils are petroleum products and heavy metals [82]. In many urban areas, past industrial activities have resulted in thousands of contaminated sites that require decontamination prior to any further utilization. Estimates by the province’s ministry of environment have shown that, in the region of Montreal alone, there are over 1350 contaminated sites of which only 54% are in the process of being rehabilitated by traditional methods [83]. Current decontamination methods imply the excavation of the contaminated soils, transport to a landfill treatment facility followed by chemical cleaning, vitrification, incineration or dumping; these steps are extremely expensive [84]. Plant-based in situ decontamination technologies, i. e. phytoremediation, represent a cost-effective alternative [84]. Plants have the capacity to accumulate, translocate, concentrate, or degrade contaminants in their tissues. Phytoremediation takes

advantage of the microbial communities (bacteria and fungi) present in soils to increase the potential of plants to uptake pollutants from the soil matrix. Willows are among the species most widely used for phytoremediation, given their diversity and tolerance of high levels of contaminants [85]. Also, willows develop an extensive root system that stimulates rich and diverse microbial communities that are involved in the degradation of organic pollutants, These characteristics, combined with exceptionally high biomass production, make them very suitable for phytoremediation [86].

Phytoremediation using willows is becoming an increasingly popular alternative approach to decontamination, and several studies and pilot projects are underway. Willows have been used successfully to treat highly toxic organic contaminants such as PCBs, PAHs, and nitro — aromatic explosives [87]. Similarly, willows, in particular S. viminalis and S. miyabeana, have been shown to accumulate Cd and Zn in their stems and leaves while sequestering Cu, Cr, Ni and Pb in their roots [85,88,89,90]. In previous studies, the efficiency of willows in short — rotation intensive plantation for the elimination of heavy metals contained in wastewater sludge has been investigated [28, 59, 90]. We have also found that willow may be useful for improving sites polluted by mixed organic-inorganic pollution [91] (Figure 8).

Figure 8. Phytoremediation using willows on a former oil refinery around Montreal

Although the fast-growing perennial habits of short-rotation coppice willow planted at high densities result in a low concentration of metals accumulated in biomass after one year of growth, the high biomass production of Salix spp. over several harvesting cycles (2-3 years) allows them to accumulate large quantities of metals over the long-term, suggesting great potential as a phytoremediation tool.

Species characteristics and natural distribution of willows

The genus Salix comprises about 350 to 500 different species worldwide [14] and is taxonomically complex and difficult to arrange in distinct sub-groups, probably due to intersectional and intersubgeneric polyploidy [15]. About 10% of the willow species consist of deciduous tree species, some of which may attain a height of > 20 meter. However, the vast majority consists of multiple stemmed trees and shrubs, and also a number of very short procumbent species can be found, not exceeding the height of the herb-layer in which they reside. Willow mainly is a boreal-arctic genus, with its natural distribution primarily in the northern hemisphere. Most willow species are found in China and in the former Soviet Union, and some indigenous species are present in India and Japan. The genus also occurs naturally in the southern hemisphere in Africa and in Central — and South America [14], and has been introduced in Australasia and New Zealand. Many species have been transferred beyond their natural range. The short rotation coppice systems currently in use in Sweden are mainly based on Salix viminalis, which was introduced in the 1700’s from continental Europe for the purpose of basket making, and on their hybrids with S. burjatica and S. schwerinii, recently introduced from Siberia.

Early records of willow cultivation date from 2000 years ago in the Roman Empire and in modern times willow breeding and selection programs have been recorded from Sweden, the UK, Belgium, France, Croatia, Poland, Hungary, former Yugoslavia, Romania, Bulgaria and China, but also outside Eurasia in New Zealand, Argentina, Chile, Canada and in the USA. The development of molecular methods in plant breeding is likely to speed up the selection of new and viable material [16] and is envisaged to lead to a willow crop which is less prone to pests and diseases and which can be managed with lower inputs than the current systems [17].

The widespread interest in the willow genus is due to the fact that many of its species, which are light demanding pioneer trees, exhibit a very high growth rate in their juvenile stage. Many willow species can easily be propagated by means of cuttings, and most species and their hybrids will generate new shoots abundantly after cutting down older shoots and stems [18]. Under Swedish conditions, willow has a very high and well documented growth potential [19] which, though, is not completely realized in commercial short rotation forestry [20]. To fully exploit the growth potential of willows, a soil fertility level is required which is comparable with those found on conventional agricultural soils in Sweden. To maintain growth in the long term, dry sites have to be avoided and nutrients have to be added at a rate which balances nutrient removal by harvest. Compared to conventional forestry, willows require a relative intensive management, but compared to conventional agricultural practice, management input is much lower.