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- Biotechnology for Biofuel Production and Optimization - Knovel
The technologies to produce the first-generation biofuels from edible sugars and starches are mature and well understood, and production is primarily limited by environmental and social concerns such as competition for land and water used for food and fiber production causing increase in world commodity prices for food and animal feeds Sims et al. These lignocellulosic feedstocks include woody biomass and wood wastes, crop residues, dedicated energy crops such as switchgrass, municipal wastes, and algae. These next-generation feedstocks do not compete directly with food production and can often be produced on marginal or unused croplands.
Furthermore, lignocellulosic biomass is an abundant renewable energy source, with the potential to displace a large portion of conventional energy resources such as fossil fuels and natural gas for the future production of liquid biofuels with improved environmental benefits. As a result, lignocellulosic biomass holds promise as a feedstock for a biorefinery where sugars can be transformed into building-block chemicals through fermentation, enzymatic, and chemical transformations Ragauskas et al.
Lignocellulosic biomass is a composite structure of lignin, cellulose, and hemicellulose polymers. The efficient utilization of biomass for biofuels production requires a fractionation of biomass constituents into separate streams at maximum yields. However, a major barrier to lignocellulosic biomass utilization in any sugar platform biorefinery is its intrinsic resistance to deconstruction. This recalcitrance results from multiple factors including the heterogeneous nature of the polymer matrix, the complexity of lignin and hemicellulose spatial and chemical interactions, and the extensive hydrogen bonding of crystalline cellulose.
Therefore, investigating plant cell wall biosynthesis to unravel the recalcitrant structure of lignocellulosic biomass, exploring the types of pretreatment processes used to deconstruct biomass, and developing efficient enzymatic hydrolysis are main focus areas in converting the polymeric carbohydrates present in plant biomass to fermentable sugars for cost-effective ethanol production.
In the biochemical conversion of biomass to ethanol, a pretreatment step is conducted to reduce the recalcitrance of biomass to realize the high yields vital to an economically favored commercial process. Pretreatment can be an effective method of hydrolyzing the hemicellulose or removing a fraction of the lignin, thus increasing the accessibility of the remaining cellulose to enzymatic hydrolysis and increasing enzymatic hydrolysis rates and extents.
Pretreatment with mineral acids are very common, e. Recently, ionic liquids have been shown to completely solubilize biomass and are considered promising solvents for the pretreatment of biomass Shill et al. However, all of these chemicals have issues with large-scale processes. Acids are corrosive and requires the use of expensive equipment metallurgy and waste handling, bases are expensive and also require neutralization steps, ionic liquids are even more expensive at present and can be toxic at low concentrations, requiring very efficient recovery processes.
All of these factors add cost and can make the overall process environmentally unfriendly and economically unattractive. Therefore, environmentally benign, low cost pretreatment technologies are constantly being investigated. As with any process involved in biomass conversion, high yields are required for maximal biomass utilization with minimized losses.
Due to its rigid structure and high crystallinity, cellulose provides the basic framework for plant fibers and is resistant to chemical or enzymatic hydrolysis. The enzymatic hydrolysis of cellulose is a slow process and the extent of hydrolysis is influenced by the structural properties of the biomass substrate, such as crystallinity, surface area, degree of polymerization, and porosity Yoshida et al.
To increase the efficiency and efficacy of the enzymatic hydrolysis process, it is generally necessary to perform a chemical pretreatment of the biomass to modify one or more of these attributes, thereby allowing better access by cellulase enzymes to cellulose. Furthermore, efficient enzymatic hydrolysis of cellulose requires the synergistic action of several cellulolytic enzymes produced by various fungal and bacterial microorganisms Himmel et al. The mode of action of cellulolytic enzymes on cellulose chains is commonly described by the synergistic action of endo-acting enzymes that randomly cleave bonds along the cellulose chain, and processive exo-acting enzymes that degrade the polymers from chain ends Teeri ; Horn et al.
Despite the availability of detailed knowledge on cellulase structure and on the molecular properties and ultrastructure of cellulose, the complexity of biomass and its interactions with cellulase limit our understanding of the mechanism of efficient hydrolysis of recalcitrant cellulose. Consequently, new studies focused at understanding the mechanism for improving cellulase efficiency and productivity are at the forefront of biochemical and biotechnology research focused on transforming biomass to biofuels.
The research and development efforts of various organizations are focused on the fundamental understanding and elimination of biomass recalcitrance—the resistance of cellulosic biomass to breakdown into sugars.
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The development of new biomass feedstocks by altering plant cell walls via genetic manipulation of the cell wall polymer biosynthesis pathway is a very active research area. Generating cell walls with reduced recalcitrance requires detailed characterization of both plant cell wall chemistry and structure. However, to identify changes in cell wall properties resulting from genetic manipulation of specific genes in these pathways requires screening of large number of mutant plants.
High throughput HTP analytical techniques for screening and characterizing cell wall components of large sample sizes of mutant plants are essential Foston and Ragauskas ; Gjersing et al. Recent developments have significantly advanced our ability to screen large number of plant variants for changes in recalcitrance, however these techniques require specialized equipment and expensive robotics Selig et al.
Newer, cheaper, and less complex means of measuring this recalcitrance is still needed. Similarly, understanding the cell wall composition of these same large sample sets is also a challenge. The current standard analytical technique for quantifying biomass cell wall components utilizes a two-stage acid-hydrolysis followed by high-performance liquid chromatography HPLC and gravimetric determinations, which are both time and labor intensive Gjersing et al.
Therefore, new HTP analytical technologies for faster and more accurate determination of cell wall components are essential to make the entire process truly high throughput and cost-effective.
Consequently, the availability of simple and universal HTP analytical techniques to characterize the composition, chemical structure and morphology of a biofuel feedstock will be vital in identifying and overcoming biomass recalcitrance and producing economical biofuels and biomass-derived chemicals. Research in the production of biofuels has been growing significantly due to rising energy prices and the depletion of fossil fuels reserves. Cellulosic biomass offers an abundant and largely untapped resource for biofuels, if optimal and cost-effective conversion methodologies are determined.
Biotechnology is being used to produce new advanced biofuels that perform more like gasoline, providing better fuel economy and fewer blending issues than ethanol. The scope of biofuel biotechnology spans feedstock chemistry, degradation processes, and variations in technology.
This special issue addresses important recent developments related to biochemical conversion of biomass and is dedicated to advance new developments, approaches and progress in the understanding of application of biotechnology research for the efficient production of biofuels. The special issue includes original full research articles, short communications, methods and review papers. National Center for Biotechnology Information , U.
Journal List 3 Biotech v. Published online Feb The BB 4 allows for the establishment of the interactions among methanol per oil mole ratio X 1 , catalyst concentration X 2 , reaction temperature X 3 and reaction time X 4 through a valid model that relates these factors conditions to biodiesel yield regression analysis , as well as the justification of the optimum conditions for biodiesel production Table 4. Trans-esterification: The KOH catalyst was dissolved completely in the required amount of methanol as specified in the experimental design to form a clear solution of potassium methoxide.
The mixture was enclosed, maintained at the specified temperature and continuously stirred at rpm on a "7. The products obtained were transferred to separating funnel and allowed to stand for 24 h.
The products separated into two distinct layers, a light yellow top layer biodiesel and a reddish brown bottom layer glycerol. Biodiesel from vegetable sources offer complementary contributions to the global energy solution in technical, economic and environmental terms, particularly in developing countries where the energy crisis is further exacerbated by the poor level of technical knowhow, poor economic power of a large proportion of the population and the resultant environmental impoverishment that the continued energy crisis in such regions will bring The results of the present study offers an inexpensive, easy and low-tech means of converting waste oils into viable economic energy products, while eliminating a secondary pollutant generated across a wide range of the society from household to eateries, hotels and related establishments, highlights the potential of such energy sources and further expand the opportunities inherent in the adoption of such methodologies for the generation of energy products.
Biodiesel yield: Figure 2 - 4 , show the effects of the variation in 4 parameters methanol per oil mole ratio, catalyst concentration, reaction temperature and reaction time on biodiesel yields obtained during the transesterification reactions of biodiesel production. Generally, it can be said that the 4 parameters have both the main and interactive effects on the biodiesel yields. The effects of each of the four parameters can be explained largely in terms of the reversible nature of the reaction between the oils and the methanol to form biodiesel.
Main and interactive effects of reaction temperature: Increase in reaction temperature within the specified temperature range resulted in increase in the biodiesel yields in each case of the oils used Fig. That is increase in reaction temperature favored forward reaction for biodiesel production. The increased temperature caused the reactants methanol and oil triglycerides to react completely with increase reaction rate. It is important to note that the interactive effect of reaction temperature and methanol per oil mole ratio as well as reaction temperature and catalyst concentration on the yields is positive.
That is biodiesel yield increased when these parameters were increased but with an exception at the catalyst concentration of 1. As reported earlier, increase in biodiesel yield with increase in reaction temperature is consistent with Arrhenius equation, which indicates increase in rate of reaction with increase in temperature 17 - Main and interactive effects of methanol per oil mole ratio: High biodiesel yield was obtained from the three oils when the methanol per oil mole ratio used was within mole ratio Fig. This implies that incomplete reaction occurred when the methanol oil mole ratio was less than 9 and a reverse reaction at mole ratio above 10, as equally reported by earlier researchers 12 , The interactive effect of methanol per oil mole ratio and catalyst concentration on biodiesel yield indicates that catalyst concentration should be kept at 1.
The interactive effect of increase in the methanol per oil mole ratio and increase in reaction time as well as increase in reaction temperature showed an increase in biodiesel yield Fig. In addition, literatures reveal that the low yield of biodiesel at excess methanol per oil of greater than 10 mole ratio during transesterification increases the polarity of the reaction mixture, thus increasing the solubility of glycerol and this promotes the reversible reaction between glycerol and biodiesel, thereby reducing biodiesel yields 23 , Main and interactive effects of catalyst concentration: In each case with the three waste oils employed in the present study, increase in catalyst concentration up to 1.
As reported earlier, catalyst concentration of 1. Beyond this concentration, decrease in biodiesel yields due to saponification reaction sets in, resulting mainly from the reaction between the excess catalyst and methanol to form soap, which inhibits biodiesel yield 20 , 21 , The interactive effect of catalyst concentration and the reaction time reveals that the reaction time should be kept at 80 min to promote the forward reaction and thus ensure favorable biodiesel yield. Main and interactive effects of reaction time: Increase in reaction time favors the forward reaction for biodiesel production.
In the present study, the main effect of reaction time on biodiesel yield showed biodiesel yield increased with reaction time. Earlier reports showed that providing sufficient time during transesterification reaction drive the reaction forward into completion for biodiesel production 12 , 18 , 20 , Also, the interactive effect showed high yield of biodiesel at methanol per oil mole ratio of 9, catalyst concentration of 1. Biodiesel yield models: The general response biodiesel yield models, as function of the four parameters, are second-order polynomials, which can be represented in the form Eq.
From the regression analysis, the most fitted models obtained are as shown in Eq.pierreducalvet.ca/62372.php
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Analysis of variation using p and f-values: The ANOVA for the three regression models of biodiesel yields obtained indicates that the models fit well in describing the relationship between the predictor biodiesel yields and the factors. This is evident from the calculated high f-values and low p-values Table 5. Each model has high values of R 2 and R 2 adjusted and these values show the suitability of the models by describing the extent to which responses are reflected.
Equation 2 indicates the significance of the effect of methanol per oil mole ratio and also the interactions of the four parameters on WGO biodiesel yield.
Biotechnology for Biofuel Production and Optimization - Knovel
This was justified by the low p-values and high f-values obtained Table 5. Methanol per oil mole ratio and reaction time, as well as the squared terms of the four parameters have significant effects on WSO biodiesel yield model Eq. In addition, the effects of the interactions of both the catalyst concentration with reaction temperature with reaction time are significant for WSO biodiesel yield as reflected by the low p-values and high f-values of the coefficients of the model equation Table 5.
The high f-value and low p-value that resulted in the omission of reaction time in Eq. In addition, low p-values and high f-values of these interactions and squared reaction temperature term indicates their significance. Optimal conditions for biodiesel production: Table 6 shows the optimal conditions for biodiesel production from the three waste oils.
Considering the three waste oils employed, the optimum methanol per oil mole ratio range was 9. From the table, optimum value range obtained for biodiesel production from waste oils are, 0. Properties of the biodiesel obtained: In the present study, biodiesel properties obtained were within the ASTM standards, indicating that high quality biodiesel were obtained from the three oils 28 - 30 Table 7. Water content determined in all the cases were of insignificant levels, making the biodiesels of good quality. In this study, high quality biodiesels consistent with ASTM standards for non-petroleum diesel, with higher cetane number and better engine ignitability were generated from three waste oils by transesterification process using KOH as catalyst.
Biodiesel conversion from waste oils will reduce use of virgin oils for biodiesel, reduce pollution and the cumulative cost of acquiring energy, improved recycling and improve livelihood. Abila, N. Biofuels adoption in Nigeria: A preliminary review of feedstock and fuel production potentials. Ushie, F. Abam, M. Agba and J.