DM concentration is an important parameter to design the biogas reactor size and calculate capacity of a biogas plant such as an electrical power installation [2]. Too diluted animal slurry reduces economic viability but too high DM, for example higher than 15% DM, may cause a pumping problem. It is generally said that 10% DM is optimal.

The slurries included in this study had a wide range of DM contents (Table 2). It ranged between 34.1 (mink) to 238.6 kg-1 (calf). The highest DM was found in calf manure, since the majority was composed of straw bedding materials, but currently calf slurry is not used for biogas production in Denmark. DM concentration of all the tested samples was 9.7% of the mean value, close to the optimal DM concentration. However excluding the calf manure that is not used for biogas production, the mean DM concentration is much lower. Indeed, the DM concentration of the biogas reactor to which most of the manures tested were fed was 5.8%. As can be seen in Table 2, particularly piglet and mink manure have very low content of DM, which approximately amounts to 3-5% DM of total mass.

Compared to the large variation of DM concentration within and between manure groups (See Figure 3), the VS concentration (as a percentage of DM) varies much less. Table 2 shows that VS concentration varies between 70 to 90% of DM. The VS concentration is crucial to determine organic loading rate, and determines the methane yield. The variation of VS as a percentage of fresh weight is large, since VS is the organic fraction of DM.

An acetone — butanol — ethanol blend (in a ratio of 3-6-1) may serve as an excellent car fuel, which can be easily mixed not only with petrol but also with diesel. ABE as a fuel additive has the advantage of a similar heat of combustion to hydrocarbons, and perfect miscibility with hydrocarbons, even when water is present. The fermentative production of ABE used to be the second largest industrial fermentation after ethanol production [5]. Product inhibition caused principally by butanol is the main problem that hindering commercial development of the fermentation process. One way to overcome this inhibition problem

would be to couple the fermentation process to a continuous product removal technique, so that inhibitory product concentrations are never reached. However, even with continuous product removal, product formation in these systems does not proceed indefinitely, because of the inhibition caused by the accumulation of mineral salts in the reactor [96]. Due to the shortage of raw materials, namely corn and molasses, and to decreasing prices of oil, ABE fermentation is not profitable when compared to the production of these solvents from petroleum. During the 1950s and 1960s, ABE fermentation was replaced by petroleum chemical plants.

Currently, the production of mixtures of acetone, butanol and ethanol (ABE) by sugars derived from lignocellulosic feedstocks continues to receive attention because of its potential commercial significance. The traditional fermentative production of acetone — butanol — ethanol is batch anaerobic bacteria fermentation with Clostridia. The substrate consists of molasses, and phosphate and nitrogen sources. Instead of molasses other sugar sources like sugar from lignocellulosic feedstock can also serve as a raw material for fermentation [97].

Fig. 4 illustrates the distributions of selected compounds in bio-oil, MF, and HF. Six chemicals were selected as being representative of ketones, aldehydes, phenols, and sugars, respectively. 1-Hydroxy-2-propanone, the most abundant ketone in bio-oil, could not be detected in the MF or HF after separation, indicating that it was extremely enriched in the

enrichment of small ketone and aldehyde molecules in the LF. Phenol appeared to be difficult to separate as there were similar distributions in bio-oil, MF, and HF. In contrast, compounds of higher molecular weight tended to be enriched in the MF and HF. For example, 1,2-benzenediol and 3-methyl-1,2-benzenediol were more abundant in the MF and HF than in the bio-oil before separation. In particular, the relative content of 1,2-benzenediol amounted to 11.73 wt% in HF, about five times higher than that in bio-oil (2.45 wt%).

Within the anaerobic and aerobic environment, various important parameters affect the rates of the different steps of the process, i. e. pH and alkalinity, temperature, and hydraulic retention times.

Each group of microorganisms has a different optimum pH range. Methanogenic bacteria are extremely sensitive to pH with an optimum between 6.5 and 7.2 pH, alkalinity and volatile acids/alkalinity ratio. The fermentative microorganisms are somewhat less sensitive and can function in a wider range of pH between 4.0 and 8.5. at a low pH the main products are acetic and butyric acid, while at a pH of 8.0 mainly acetic and propionic acid are produced.

The temperature has an important effect on the physicochemical properties of the components found in the digestion substrate. It also influences the growth rate and metabolism of microorganisms and hence the population dynamics in the anaerobic reactor. Acetotrophic methanogens are one of the most sensitive groups to increasing temperatures. The degradation of propionate and butyrate is also sensitive to temperatures above 70 °C. The temperature has moreover a significant effect on the partial pressure of H2 in digesters, hence influencing the kinetics of the syntrophic metabolism. Thermodynamics show that endergonic reactions (under standard conditions), for instance the breakdown of propionate into acetate, CO2, H2, would become energetically more favourable at higher temperature, while reactions which are exergonic (e. g. hydrogenotrophic methanogenesis) are less favoured at higher temperatures.

The solids retention time (SRT) is the average time the solids spend in the digester, whereas the hydraulic retention time (HRT) is the average time the liquid sludge is held in the digester. The subsequent steps of the digestion process are directly related to the SRT. A decrease in the SRT decreases the extent of the reactions and viceversa. Each time sludge is withdrawn, a fraction of the bacterial population is removed thus implying that the cell growth must at least compensate the cell removal to ensure steady state and avoid process failure [28].

In another experiment, different levels of protein from two kinds of artemia meal include artemia meal from Urmia lake and artemia meal from earth ponds beside Urmia lake with levels of 0, 25, 50, 75, 100 percent replaced to prue fish meal protein [12]. The experimental design was completely randomized with factorial method; include 10 treatments and 3 repetitions that in each repetition there were 10 one day-old male broilers from Ross 308 strain. This experiment was performed in 7 weeks and during and end of it, traits that related to broiler performance and carcass, was measured and analyzed. Results showed that effect of kind of artemia meal and effect of level of protein replacement weren’t significant for feed intake. But interaction between these two was significant for this trait (P<0.05). The highest feed intake belong to Urmia lake artemia meal treatment with 50% level of replacement and the lowest feed intake related to treatment of without artemia meal (contain 5% fish meal). For body weight gain and feed conversion ratio, effect of kind of artemia meal and effect of level of protein replacement and effect of interaction between these two weren’t significant. These effects weren’t significant for all carcass traits and gastro intestinal parts exception for femur percent that treatment of without artemia meal (contain 5% fish meal) had a lowest percent to comparison with other treatments for this trait.

5. Conclusion

Results of this studies revealed that artemia meal can be used as a feedstuff in poultry and other farm animal’s diets because it has high level of protein and high protein digestibility. Compared with other animal proteins, artemia does not contain any feather, bone, hair or gastrointestinal tract components. In addition, in artemia production there is no requirement for high pressure and high temperature treatments which can influence protein quality. Artificial culture of artemia is easy and is possible everywhere.

Author details

A. Zarei[5]

Department of Animal Science, College of Agriculture and Natural Resources, Islamic Azad

University — Karaj Branch, Karaj, Iran

Exponential growth in batch fermentation may be prolonged by adding of fresh medium to the vessel. In the continuous fermentation process, the added medium displaced an equal volume of culture from the vessel. Thus, the process of continuous fermentation non-stop and the exponential growth will proceed until the substrate is exhausted. By using proper technique, the desired products are obtained from the removed medium [13].

If medium is fed continuously to such a culture at a suitable rate, a steady state is eventually achieved i. e., the formation of new biomass by the culture is balanced by the loss of cells from the vessel. The flow medium into the vessel is related to the volume of the vessel by the term dilution rate, D, defined as:

d = f/v

Where F is the flow rate (volume units/time) and V is the volume (volume units).

The net change in cell concentration over a time period may be expressed as:

^x/dt = growth — output

dx/dt = gx-Dx

Under steady state conditions the cell concentration remains constant, thus = 0 and:

g = D

Thus, under steady state conditions, the specific growth rate is controlled by the dilution rate, which is an experimental variable. It is recalled that under batch culture conditions, an organism will grow at its maximum specific growth rate and, therefore, continuous culture may be operated only at dilution rates below the maximum specific growth rate.

Le Duc Dung, Kayoko Morishita and Takayuki Takarada

Additional information is available at the end of the chapter http://dx. doi. org/10.5772/55356

1. Introduction

Tar is a viscous black liquid derived from pyrolysis of organic matter as well as a complex mixture of hydrocarbons. The presence of tar in product gas may cause blockage and corrosion of equipment and be responsible for fouling or reducing overall efficiency of processes. By far, tar removal is the most problematic during biomass gasification. Hence, the successful implementation of gasification technology for gas engine, gas turbine or fuel cell based power projects depends much on the effective and efficient removal or conversion of tar from the product gas. Beside that the catalytic steam reforming tar is one of the most promising methods to suppress the problems. Biomass product gas is usually low high heating value; therefore enhancement of product gas quality is other important target. We propose a research topic that use of nickel loaded brown coal char as a new catalyst for decomposing tar from biomass gasification in fluidized bed gasifier. The method is promising to achieve some advantages of low cost by use of low rank coal as catalyst support material, high catalyst activity and enhancement of product gas quality. Yallourn brown coal has been selected for preparing catalyst support. The coal is low rank with high moisture content, low heat value and high oxygen content. It is hard to use for generating energy. However, it has many outstanding features such as less ash and sulfur content, and including abundant of oxygen-containing functional groups such as carboxyl and phenol groups which are available for ion-exchange with metals. In this research work, a nickel loaded brown coal char (Ni/BCC) was prepared by ion-exchange method, dried at 380 K in nitrogen for 24 h, and then pyrolysed at 923 K in nitrogen for 90 min. The works have been carried out is that using nickel loaded brown coal to decompose tar in pyrolysis and steam gasification process. It was carried out in a two-stage fixed-bed reactor and a lab scale fluidized bed gasifier under mild conditions (temperature, steam, space velocity, operation time). Inside of gasifier is constructed by two beds, the primary one is a fluidized bed with sand, and the second one is a catalyst bed. The new catalyst has shown high catalytic

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activity and stable activity and given the high quality of product gas in presence of steam, approximately 90% of biomass tar was decomposed and useful gas components (CH4, CO, and H2) yields were higher than those of Ni/AhO3 catalyst. Ni/BCC catalyst was characterized and exhibited good dispersion of nickel particles, ultra-fine Ni less than 15 nm and having a large surface area about 350 m2/g. Moreover, at the end of catalyst life span, the catalyst can be disposed of simply by gasifying/burning the coal char, during which the energy value of the char support can be recovered. Also, the agglomerated nickel residues could be used as functional materials of powder metallurgy and battery development. The general results suggest that the Ni/BCC catalyst offers a potential to be used as a tar steam reforming catalyst in biomass gasification.

Various process configurations are possible for the production of bioethanol from lignocellulosic biomass, the most common method for bioethanol conversion technology from lignocellulosic biomass involves three key steps:

Pre-treatment : During biomass pre-treatment lignocellulosic biomass is pre-treated with acids or enzymes in order to reduce the size of the feedstock and to open up the plant structure. Normally, the structure of cellulosic biomass is altered; lignin seal is broken, hemicelluloses is reduced to sugar monomers, and cellulose is made more accessible to the hydrolysis that convert the carbohydrates polymers into fermentable sugars.

Hydrolysis: This is a chemical reaction that releases sugars, which are normally linked together in complex chains. In early biomass conversion processes, acids were used to accomplish this. Recent research has focused on enzyme catalysts called "cellulases" that can attack these chains more efficiently, leading to very high yields of fermentable sugars. Although the decomposition of the material into fermentable sugars is more complicated, the fermentation process step is basically identical for bioethanol from either food crops or lignocellulosic biomass.

Fermentation : Microorganisms that ferment sugars to ethanol include yeasts and bacteria. Research has focused on expanding the range and efficiency of the organisms used to convert sugar to ethanol.

The aim of combination is to enhance alkaline or acidic intensity of liquid hot water by ammonia or carbon dioxide for lignocelluloses fractionation.

Ammonia is an extremely important widely used bulk chemical. The polarity of Ammonia molecules and their ability to form hydrogen bonds explains to some extent the high solubility of ammonia in water. In aqueous solution, ammonia acts as a base, acquiring hydrogen ions from H2O to yield ammonium and hydroxide ions.

NH3(aq) + H2O(l) = NH4+(aq) + OH-(aq)

The production of hydroxide ions when ammonia dissolved in water gives aqueous solutions of ammonia the characteristics of alkaline properties.

Carbon dioxide can be considered as an ideal solvent for the treatment of natural products, because of the relatively low critical pressure (73.8 atm) and critical temperature (31.1 °C), it. In contrast with organic solvent, Super-critical carbon dioxide is non-toxic, non-flammable, non corrosive, cheap and readily available in large quantities with high purity [171].

Carbon dioxide dissolves in water becomes acidic due to the formation and dissociation of carbonic acid:

CO2 + H2O = H2CO3 = H+ + HCO3-

Over the temperature range 25-70 °C and pressure range 70-200 atm, the pH of solution ranged between 2.80 and 2.95, and increases with increasing temperature and decreases with increasing pressure [172]. It was shown that in the presence of water, supercritical CO2 can efficiently improve the enzymatic digestibility of lignocellulosic materials [32].

There is much evidence that most newly-established willow plantations profit immensely from being cut back at the end of the first growing season (Figure 3).

Not only does cutback encourage established cuttings to produce vigorous multiple shoots the following spring, it also helps reduce competition by weeds, thereby reducing the need for continued chemical weed control [38]. Furthermore, cutback facilitates entering the field at the beginning of the second growing season to fertilize and till soil between rows. Cutback is normally performed in the fall by cutting all newly-formed shoots at ground
level using conventional agricultural equipment, such as reciprocating mowers for large surfaces or a trimmer/brush-cutter for small plots.