3.1. A molecular distillation apparatus

Fig. 2 shows a KDL-5 wiped-film molecular distillation apparatus used for bio-oil separation research at Zhejiang University, which was manufactured by UIC Corporation in Germany. It consists of four main units, namely a feeding unit, an evaporation unit, a condensation unit, and a reduced pressure unit. The feeding unit mainly comprises a graduated dosing funnel with a double jacket, which is filled with heat-transfer oil to control the temperature and to ensure free flowing of the feedstock. The evaporation unit comprises a cylindrical evaporator with a surface area of 0.048 m2, encased in a double jacket containing heat- transfer oil to maintain good temperature homogeneity. It is worth noting that all of the temperatures of these sections are independent. The condensation unit has two cold traps. The first cold trap (or internal condenser) is located in the center of evaporator, and condenses the volatile compounds reaching the cooling surface. There is another cold trap to prevent uncondensed volatile organic compounds from entering the pump. In the reduced pressure unit, the condensation temperature is usually set at -25 °C. The evaporation temperature ranges from room temperature to 250 °C, while the operating pressure can be as low as 5 Pa.

The bio-oil used at Zhejiang University was produced from a bench-scale fluidized bed fast pyrolysis reactor (Wang et al., 2008). Crude bio-oil often contains some solid particles, which would abrade the evaporator surface and block the orifice of the dosing funnel, so it is necessary to perform some pre-treatments. Centrifugation and filtration are usually used to remove the solid particles, and traditional reduced pressure distillation can also be used to remove water and volatile compounds. The pre-treated bio-oil is placed in the funnel and then the separation process starts. The volatile components released from the thin liquid film are condensed by the internal condenser to form the distilled fraction, while the heavy compounds that are not vaporized flow along the evaporator surface and are collected as the residual fraction.

Because of the short residence time of the feed material at the evaporation temperature, this gentle distillation process only puts a low thermal load on the materials to be distilled. It is therefore appropriate for the separation of bio-oil, which is thermally unstable.

1.1.2. Biochemical characterization and selection of strains

To grow, microorganisms from the environment should take all the substances required for the synthesis of their cellular materials and power generation. These substances are known nutrients. A culture medium should contain, therefore, all the necessary nutrients in appropriate amounts in the specific requirements of the microorganisms to what has been devised. At selected strains were performed the following biochemical tests, in order to know their identification: catalase production, nitrate reduction, mobility, indole production, the use of citrate as a carbon source, production of urease, methyl red, Voges — Proskauer, carbohydrate fermentation, starch hydrolysis, gelatin hydrolysis and hydrolysis of esculin [40,41]. To determine resistance to low pH, this is changed in the culture media from 3 to 6. The pH was measured with a potentiometer, is adjusted with 10 M NaOH (sodium hydroxide) and HCl (hydrochloric acid).

The chemical composition of different kinds of artemia meal (dried at 50-60°C as sun cured or oven dried) is shown in Table 1. As shown in table 1, the chemical composition of 3 kinds of artemia meal (collected from different regions of Iran) is not identical. The quality of those, depends on region, species, time of harvest and percentage of artemia mixture (artemia in different stages of living shows different compositions). So prior to using this ingredient, it must be analyzed for main nutrients.

There are basically three modes of fermentation process: (1) Batch fermentation process. (2) Fed batch fermentation process and (3) Continuous fermentation process (Figure 1).

Batch Fed batch Continuous

The mode of operation is dictated by the type of product being produced.

The fermentation process may be divided into six phases:

a. The formulation of media to be used in culturing the process organism during the development of the inoculum and in the production fermenter.

b. The sterilization of the medium, fermenters and ancillary equipment.

c. The production of an active, pure culture in sufficient quantity for inoculating the production vessel.

d. The growth of the microorganism in the production fermenter under optimum conditions for product formation.

e. The extraction of the product and its purification.

f. The disposal of effluents produced by the process.

The interrelationships between the six phases are illustrated in Figure 2.

The RESETA project has focused a basic model of biorefinery for producing up to 45,000 liters ethanol/year; 450.000 liters fertilizer. This concept includes the production of ethanol, biogas, biodiesel, fertilizers and animal food (Figure 4). The whole plant is installed in an area of 1,200 m2.

Anaerobic digestion module

Heat

generation

Pretreatment

module

Disti Nation module

Saccharification

and

Fermentation

modu e

Figure 4. Isometric plan of the biorefinery built for the RESETA project.

This biorefinery is also able to produce first and second generation ethanol from sugar, starch or cellulose containing feedstocks. From that point of view, the biorefinery concept can be applied not only to large scale, but also in mid and small scale production. In Ecuador, there are communities that produce a wide variety of residues that can be utilized. The biorefinery concept is applicable to promote a sustainable economy in vulnerable and underdeveloped zones.

An important achievement of this R&D project was the development of local technology in order to reduce the dependence of foreign technicians. The RESETA project biorefinery is completely automated which permits the operators scoring historical data of the trials performed during experimentation. Researchers and engineers are working together in the optimization of processes and designs. The resulting ideas and philosophy are being of great value looking forward the future technological independence in these strategic issues for Ecuador.

Bioethanol can be produced either from conventional or advance biofuel technologies depending on the state of sugars polymerization. The predominant technology for producing bioethanol is through fermentation of sucrose from sugar crops such as sugarcane, sugar beet and sweet sorghum. Bioethanol produced from sugar or starchy materials is categorize under the conventional technology and the bioethanol so called first generation bioethanol. Whereas, at present, much focus is on the bioethanol produced from biomass that possesses lignocellulosic content. This second generation bioethanol or cellulosic ethanol could be produced from abundant low-value material, including wood chips, grasses, crop residues, and municipal waste.

Regardless of the bioethanol technologies used to produce bioethanol, the bioethanol process have to undergo several treatment steps in which normally involves pre-treatment, extraction of fermentable sugars and fermentation. Pre-treatment process mainly deals with the preparation of the feedstock into smaller size (higher surface to volume ratio) for ease of sugars extraction. Whereas, extraction process with the aim of transforming the various sugars polymer chains into simple fermentable sugars. Fermentation process is a biological process in which fermentable sugars are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products in the absence of oxygen (anaerobic process) using Saccharomyces cerevisiae. The theoretical yield of bioethanol is 0.51 g per one gram of glucose consumed during fermentation.

The efficiency of lignocelluloses utilization can be significantly improved by fractionation [40]. Fractionation of lignocellulosic materials may be achieved by various physical, chemical and biological methods. Combination of different methods may lead to more efficient fractionation processes of lignocellulosic materials [5].

The most promising combined technology for LCF fractionation is the combination of liquid hot water (LHW) with the assisted technologies, which usually are performed before or during the LHW fractionation, including steam explosion, CO2 explosion, Ammonia fibre explosion (AFEX), acid or alkaline pre-treatment, High energy radiation pre-treatment, Wet oxidation and Ozonolysis etc.

2.2.1. Combination with steam explosion

Steam explosion is the most widely employed physical-chemical pre-treatment for lignocellulosic biomass. It is a hydrothermal pre-treatment in which the biomass is subjected to pressurised steam for a period of time ranging from seconds to several minutes, and then the pressure is suddenly reduced and makes the materials undergo an explosive decompression. The treatment leads to the disruption of the structure of the material due to the rapid expansion of the water vaporized inside it. The temperatures involved are higher than, or close to, the glass transition temperature of hemicellulose, lignin and cellulose impregnated with water [142, 143], so that the internal cohesion of lignocelluloses is weakened and disaggregation and defibration of the material are facilitated. This pre­treatment combines mechanical forces and chemical effects due to the hydrolysis (auto­hydrolysis) of acetyl groups present in hemicelluloses.

Hydrolytic treatments of lignocellulosic biomass by saturated steam, with (un-catalyzed) and without (catalyzed) addition of small amounts of mineral acids, have been widely studied as a method to weaken the lignocellulosic structure and increase its chemical reactivity and enzyme accessibility [144, 145].

Un-catalyzed steam-explosion is one of only a very limited number of cost-effective pre­treatment technologies that have been advanced to pilot scale demonstration and commercialized application [16]. Autohydrolysis takes place when high temperatures

promote the formation of acetic acid from acetyl groups; furthermore, water can also act as an acid at high temperatures. The mechanical effects are caused because the pressure is suddenly reduced and fibres are separated owing to the explosive decompression. In combination with the partial hemicellulose hydrolysis and solubilisation, the lignin is redistributed and to some extent removed from the material [146]. Catalyzed steam — explosion is very similar to un-catalyzed steam-explosion on their action modes, except that some acidic chemicals (gases and liquids), primarily including SO2, H2SO4, CO2, oxalic acid, etc. are used as catalysts to impregnate the LCF prior to steam-explosion, to improve recovering both cellulose and hemicellulose fractions [147]. It is recognized as one of the most cost-effective pre-treatment processes [148, 149]. Compared to un-catalyzed steam explosion, catalyzed steam-explosion has more complete hemicellulose removal leading to more increased enzymatic digestibility of LCF with less generation of inhibitory compounds [150]. A steam-explosion/separation process offers several attractive features when compared to the alternative hydrolysis and pulping processes. These include the potential for significantly lower environmental impact, lower capital investment, more potential for energy efficiency, less hazardous process chemicals and conditions [151]. Steam-explosion allows the recovery of all constitutive LCF components without the destructive degradation of any one component in favour of any other [152]. The process is generally followed by fractionation steps in order to separate the various components.

Willow yield varies greatly depending on both environmental and genetic factors. The genus Salix, to which willows belong, comprises 330 to 500 species worldwide of deciduous or, rarely, semi-evergreen trees and shrubs [27] and the number and variety of species along with the ease of breeding have facilitated clonal selection adapted to several goals (ornamental, silvicultural, environmental applications, etc.). However, a large number of willow species are not suitable for biomass production because of their slower growth rate. Nowadays, the exploitation of the wide biological diversity within the genus Salix is focused primarily on a few species (S. viminalis, S. purpurea, S. triandra, S. dasyclados, S. eriocephala, S. miyabeana, S. purpurea, S. schwerinii, and S. sachalinensis), whereas there has been a recent increase in the number of selected intra — and interspecific hybrid cultivars offering higher yields, improved disease resistance and tolerance of a higher planting density (Table 2).

In Quebec, the first trials for evaluating willow biomass potential began on small plots in the early 1990s with two species, one indigenous (S. discolor) and the other a European cultivar (S. viminalis 5027). Two growing seasons after establishment, their total aboveground biomass yield was very similar — between 15 and 20 t ha-1 of dry-matter per year, confirming the high potential of these two species under Quebec’s agro-ecological conditions [28]. A subsequent trial aimed at evaluating these two species comparatively with S. petiolaris Smith; both the first-tested species were shown superior to the latter in terms of biomass productivity [21]. However, since after a number of years this S. viminalis cultivar showed sensitivity to insect attacks, particularly to the potato leaf hopper, and since the risk of epidemic diseases increases as the plantation area expands, a new set of selected clones was investigated. These experiments showed that in contrast to S. viminalis’ poor performance due to high sensitivity to pests and diseases, other willow cultivars (S. miyabeana SX64 and S. sachalinensis SX61) could achieve high biomass yields [29]. Now, 10 years later, S. miyabeana (SX64) and S. sachalinensis (SX61) cultivars still provide the highest biomass yield and greatest growth in diameter and height among willows in the Upper St. Lawrence region. However, selected cultivars from indigenous (i. e. North-American) willow species, especially S. eriocephala (cultivars S25 and S546) and S. discolor (cultivar S 365), perform well and only slightly below SX64, thus making them preferable for use on large-scale plantations in Quebec due to their less rigorous maintenance requirements and sensitivity to insect and pest attacks.

New selected planting material has also been made extensively available by several willow growers interested in development of willow cultivation in Quebec and operating jointly with researchers. Agro Energie (www. agroenergie. ca) was the first large-scale commercial nursery in Quebec to produce diverse varieties of willow and has continued to expand its willow plantations across Eastern Canada. For the joint project between our research team and Agro Energie, we provide scientific expertise in terms of plantation layout, species selection, cultivation methods and management practices. The 100 hectares of land provided by Agro Energie represent an opportunity to scale up experimental technology, perfect techniques and evaluate costs and yield, using the high performance agricultural equipment necessary for large-scale commercial production.

1.2. Land preparation and weed control

Appropriate soil preparation is essential to ensure good plant establishment and vigorous growth. This is particularly true when willows are to be established on soil with low fertility or marginal land. The main goal of any land preparation operation should be to eliminate weeds, aerate soil and create a uniform soil surface for planting. Once the planting site has been chosen, the first operation to be performed is preparation of the land much as for any other agricultural crop. The productivity of trees under short-rotation intensive culture is strongly influenced by herbaceous competition. One of the first trials conducted by our research team in the early 1990s showed that weed suppression was essential to willow establishment [30]. On Quebec’s generally well-drained lands, the most common weeds are broad-leaved annuals such as white goosefoot (Chenopudium album L.) and redroot pig-weed (Amaranthus retroflexus L.), whereas on poorly drained lands, annual grasses, barnyard grass (Echinochloa crusgalli L.) and perennials such as Canada thistle (Cirsium arvense L.) and quack grass (Agropyron repens (L.) Beauv.) are more common [30]. In the case of abandoned agricultural lands or in the presence of a high concentration of weeds, one or two applications of a systemic herbicide (e. g. glyphosate 2- 4 L/ha) during the summer of the year prior to planting are strongly recommended to promote establishment. A few weeks later, the destroyed plant mass should be incorporated into the soil using a rotating plough. In Quebec, a first ploughing should be performed in the fall prior to planting. Autumn ploughing allows the soil to break down over the winter, and also increases the amount of moisture in the planting bed. Suitable equipment includes any common mouldboard, chisel or disc plough (20 — 30cm depth), following usual agronomical practices for other crops (e. g. maize). Power harrowing (15- 18 cm depth) or cross disking of the site should be carried out in the spring immediately prior to planting to ensure a flat, regular planting bed.

Microbial cells can be immobilized by cross-linking between cells, using bi or multifunctional reagents as glutaraldehyde or toluene di isocyanate.

Glutaraldehyde is a colorless liquid with a pungent odor used to sterilize medical and dental equipment is also used in water treatment industry and as a chemical preservative. However, it is toxic and can cause severe eye irritation, nose, throat and lungs, along with headaches, drowsiness and vomiting. Glutaraldehyde monomer can polymerize by aldol condensation, giving poliglutaraldehido alpha, beta unsaturated reaction typically occurs at alkaline pH [59].

The use of surplus yield models for assessment of exploited fish stocks, has becoming an tool hardly used nowadays, because the use of age structured methods with the aid of computing techniques, allow more powerful and more accuracy in the assessments. There were times when fisheries researchers devoted their efforts into that approach and more sophisticated variations of the original statements were made (Walter 1975, 1978; Csirke and Caddy 1983; Arreguin-Sanchez and Chavez 1986; Polacheck et al. 1993; Freon and Yanez 1995); however, this approach has became obsolete over time, despite its background ecological principles are still valid. However, the large variance implicit in the estimations caused by several factors, contributed in a great deal to its current lack of use. Despite this consideration, it was decided to adopt that approach in this paper, for several reasons, the first one is it accessibility and easy way to just fitting a second degree curve in the spreadsheet where a bunch of catch data involving as many species as they are exploited in the world oceans, just to have a guideline on the maximum yield level and the year when it was reached. It also provided a minimum basic requirement for the estimation the stock biomass on which fisheries of each region were based.

It is remarkable to realize that the maximum yield of the world oceans approaches very close to 100 M mt and the biomass of all the exploited stocks is near to 200 M mt. Another important point to call the attention is that in most cases, the MSY was attained more than a decade ago and that the current yield and stock biomass are nearly 40 per cent below those maxima. This is something to concern and is a possible indicator of excessive pressure on the fish stocks and in this respect those on the Antarctic seem to be the most heavily impacted by fishing activities. Evidently the over exploited fisheries have passed by several stages (Pauly et al. 1998) already pointed by other authors (Harding 1968; Feeny et al. 1990; Myers and Worm 2003) and unfortunately the perspective suggests that other world oceans apart from the Antarctic, will follow the same steps if no action is taken by the nations to ensure exploiting the sea in a sustainable way (Jorgensen et al. 2007).

Author details

Ernesto A. Chavez[6] and Alejandra Chavez-Hidalgo

Centro Interdisciplinario de Ciencias Marinas, Instituto Politecnico Nacional, La Paz, Mexico