The world is confronted with the twin crises of fossil fuel depletion and environmental degradation. The indiscriminate extraction and consumption of fossil fuels have led to a reduction in petroleum reserves. Petroleum based fuels are obtained from limited reserves. These finite reserves are highly concentrated in certain region of the world. Therefore, those countries not having these resources are facing a foreign exchange crisis, mainly due to the import of crude petroleum oil. Hence it is necessary to look for alternative fuels, which can be produced from materials available within the country. Although vegetative oils can be fuel for diesel engines, but their high viscosities, low volatilities and poor cold flow properties have led to the investigation of its various derivatives. Among the different possible sources, fatty acid methyl esters, known as Biodiesel fuel derived from triglycerides (vegetable oil and animal fates) by transesterification with methanol, present the promising alternative substitute to diesel fuels and have received the most attention now a day. The main advantages of using Biodiesel are its renewability, better quality exhaust gas emission, its biodegradability and the organic carbon present in it is photosynthetic in origin. It does not contribute to a rise in the level of carbon dioxide in the atmosphere and consequently to the green house effect. This paper reviews the source of production and characterization of vegetable oils and their methyl ester as the substitute of the petroleum fuel and future possibilities of Biodiesel production.

Biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: A review

Biodiesel, defined as the mono-alkyl esters of vegetable oils or animal fats, is an environmentally attractive alternative to conventional petroleum diesel fuel (petrodiesel). Produced by transesterification with a monohydric alcohol, usually methanol, biodiesel has many important technical advantages over petrodiesel, such as inherent lubricity, low toxicity, derivation from a renewable and domestic feedstock, superior flash point and biodegradability, negligible sulfur content, and lower exhaust emissions. Important disadvantages of biodiesel include high feedstock cost, inferior storage and oxidative stability, lower volumetric energy content, inferior low-temperature operability, and in some cases, higher NO
 x
 exhaust emissions. This review covers the process by which biodiesel is prepared, the types of catalysts that may be used for the production of biodiesel, the influence of free fatty acids on biodiesel production, the use of different monohydric alcohols in the preparation of biodiesel, the influence of biodiesel composition on fuel properties, the influence of blending biodiesel with other fuels on fuel properties, alternative uses for biodiesel, and value-added uses of glycerol, a co-product of biodiesel production. A particular emphasis is placed on alternative feedstocks for biodiesel production. Lastly, future challenges and outlook for biodiesel are discussed.

https://www.biofuelscoproducts.umn.edu/sites/biodieselfeeds.cfans.umn.edu/files/2009-moser-biodiesel_production.pdf

Biodiesel production, properties, and feedstocks

https://openscholar.dut.ac.za/bitstream/10321/1400/1/rawat__kumar__mutanda___bux_2013_aplplied_energy.pdf

Biodiesel from microalgae: A critical evaluation from laboratory to large scale production

The economically significant production of carbon-neutral biodiesel from microalgae has been hailed as the ultimate alternative to depleting resources of petro-diesel due to its high cellular concentration of lipids, resources and economic sustainability and overall potential advantages over other sources of biofuels. Pertinent questions however need to be answered on the commercial viability of large scale production of biodiesel from microalgae. Vital steps need to be critically analysed at each stage. Isolation of microalgae should be based on the question of whether marine or freshwater microalgae, cultures from collections or indigenous wild types are best suited for large scale production. Furthermore, the determination of initial sampling points play a pivotal role in the determination of strain selection as well as strain viability. The screening process should identify, purify and select lipid producing strains. Are natural strains or stressed strains higher in lipid productivity? The synergistic interactions that occur naturally between algae and other microorganisms cannot be ignored. A lot of literature is available on the downstream processing of microalgae but a few reports are available on the upstream processing of microalgae for biomass and lipid production for biodiesel production. We present in this review an empirical and critical analysis on the potential of translating research findings from laboratory scale trials to full scale application. The move from laboratory to large scale microalgal cultivation requires careful planning. It is imperative to do extensive pre-pilot demonstration trials and formulate a suitable trajectory for possible data extrapolation for large scale experimental designs. The pros and cons of the two widely used methods for growing microalgae by photobioreactors or open raceway ponds are discussed in detail. In addition, current methods for biomass harvesting and lipid extraction are critically evaluated. This would be novel approach to economical biodiesel production from microalgae in the near future. Globally, microalgae are largest biomass producers having higher neutral lipid content outcompeting terrestrial plants for biofuel production. However, the viscosities of microalgal oils are usually higher than that of petroleum diesel.

Biodiesel from microalgae: a critical evaluation from laboratory to large scale production. Appl Energy

Lignocellulosic biomass (LCB) is the most abundantly available bioresource amounting to about a global yield of up to 1.3 billion tons per year. The hydrolysis of LCB results in the release of various reducing sugars which are highly valued in the production of biofuels such as bioethanol and biogas, various organic acids, phenols, and aldehydes. The majority of LCB is composed of biological polymers such as cellulose, hemicellulose and lignin, which are strongly associated with each other by covalent and hydrogen bonds thus forming a highly recalcitrant structure. The presence of lignin renders the bio-polymeric structure highly resistant to solubilization thereby inhibiting the hydrolysis of cellulose and hemicellulose which presents a significant challenge for the isolation of the respective bio-polymeric components. This has led to extensive research in the development of various pretreatment techniques utilizing various physical, chemical, physicochemical and biological approaches which are specifically tailored towards the source biomaterial and its application. The objective of this review is to discuss the various pretreatment strategies currently in use and provide an overview of their utilization for the isolation of high-value bio-polymeric components. The article further discusses the advantages and disadvantages of the various pretreatment methodologies as well as addresses the role of various key factors that are likely to have a significant impact on the pretreatment and digestibility of LCB.

/pdf/recent-trends-in-the-pretreatment-of-lignocellulosic-biomass-27tds25s66.pdf

Recent Trends in the Pretreatment of Lignocellulosic Biomass for Value-Added Products

Biodiesel production from vegetable oil using heterogenous acid and alkali catalyst

Acid-catalyzed esterification of Zanthoxylum bungeanum seed oil with high free fatty acids for biodiesel production

Xylans inhibit enzymatic hydrolysis of lignocellulosic materials by cellulases.

Background
Due to the complexity of lignocellulosic materials, a complete enzymatic hydrolysis into fermentable sugars requires a variety of cellulolytic and xylanolytic enzymes. Addition of xylanases has been shown to significantly improve the performance of cellulases and to increase cellulose hydrolysis by solubilizing xylans in lignocellulosic materials. The goal of this work was to investigate the effect of acetyl xylan esterase (AXE) originating from Trichoderma reesei on xylan solubilization and enzymatic hydrolysis of cellulose.

/pdf/the-role-of-acetyl-xylan-esterase-in-the-solubilization-of-19grc6t9pp.pdf

The role of acetyl xylan esterase in the solubilization of xylan and enzymatic hydrolysis of wheat straw and giant reed

Considerable works have been reported concerning the obstruction of enzymatic hydrolysis efficiency by lignin. However, there is a lack of information about the influence of lignin on the adsorption of cellulases on cellulose, along with the hydrolytic activity of the cellulases adsorbed on lignin. In addition, limited discovery has been reported about the influence of additives on cellulase desorption from lignin and lignocellulosic materials. In this work, the effects of lignin on cellulase adsorption and hydrolysis of Avicel were investigated and the effects of Tween 80 on cellulases adsorption and desorption on/from lignin and corn stover were explored. The results showed that the maximum adsorption capacity of Avicel reduced from 276.9 to 179.7 and 112.1 mg/g cellulose with the addition of 1 and 10 mg lignin per gram Avicel, which indicated that lignin adsorbed on Avicel reduced surface area of cellulose and lignin available for cellulases. Cellulases adsorbed on lignin could be released by reaching new adsorption equilibrium between lignin and supernatants. In addition, cellulases desorbed from lignin still possess hydrolytic capacity. Tween 80 could adsorb onto both lignin and corn stover, and reduce the cellulase adsorption on them. Furthermore, Tween 80 could enhance desorption of cellulases from both lignin and corn stover, which might be due to the competitive adsorption between cellulases and Tween 80 on them. The presence of lignin decreased the maximum adsorption capacity of cellulases on cellulose and the cellulases adsorbed on lignin could be released to supernatant, exhibiting hydrolytic activity. Tween 80 could alleviate the adsorption of cellulases and enhanced desorption of cellulases on/from lignin and corn stover. The conclusions of this work help us further understanding the role of lignin in the reduction of adsorption of cellulases on substrates, and the function of additives in cellulases adsorption and desorption on/from lignin and substrates.

/pdf/effects-of-lignin-and-surfactant-on-adsorption-and-13y4omnpw7.pdf

Junhua Zhang

Papers

Biodiesel production from vegetable oil using heterogenous acid and alkali catalyst

Acid-catalyzed esterification of Zanthoxylum bungeanum seed oil with high free fatty acids for biodiesel production

Xylans inhibit enzymatic hydrolysis of lignocellulosic materials by cellulases.

The role of acetyl xylan esterase in the solubilization of xylan and enzymatic hydrolysis of wheat straw and giant reed

Effects of lignin and surfactant on adsorption and hydrolysis of cellulases on cellulose.