Biodiesel advantages

In addition to greenhouse benefits, biodiesels offer environmental advantages over conventional diesel. Biodiesels produce similar NO, emissions to conventional diesel, fuel but less particulate matter. Biodiesel is more biodegradable that conventional diesel making any spills less damaging in sensitive areas. In general biodiesel provides more lubrication to the fuel system than low-sulfur diesel. 

Biodiesel may be represented chemically as a mixture of fatty acid methyl esters. It is a naturally derived liquid fuel, produced from renewable somces which, in compliance with appropriate prescriptions, may be used in place of diesel fuel for both internal combustion engines and for producing heat in boilers. The advantages, especially environmental, which can potentially result from the widespread use of biodiesel, are manifold ... 

Biodiesel is a fuel derived from renewable natural resources such as soybean and rapeseed and consists of alkyl esters derived from transesterification of triglycerides with methanol. In spite of all the advantages of biodiesel, such as low emissiotts, biodegradability, non-toxicity, and lubricity, the major hurdle in penetration of biodiesel is its high cost because of the expensive food grade refined vegetable oil feedstock. 

Biodiesel is a mixture of methyl esters of fatty acids and is produced from vegetable oils by transesterification with methanol (Fig. 10.1). For every three moles of methyl esters one mole of glycerol is produced as a by-product, which is roughly 10 wt.% of the total product. Transesterification is usually catalyzed with base catalysts but there are also processes with acid catalysts. The base catalysts are the hydroxides and alkoxides of alkaline and alkaline earth metals. The acid catalysts are hydrochloride, sulfuric or sulfonic acid. Some metal-based catalysts can also be exploited, such as titanium alcoholates or oxides of tin, magnesium and zinc. All these catalyst acts as homogeneous catalysts and need to be removed from the product [16, 17]. The advantages of biodiesel as fuel are transportability, heat content (80% of diesel fuel), ready availability and renewability. The... 

To produce biodiesel grade methyl esters, the oil must be trans-esterified with methyl alcohol. This process cleaves the triglyceride to yield glycerol and the individual methyl ester compounds. Most biodiesel trans-esterification is base catalyzed and has the operational advantage of low temperature, low pressure, and high conversion rates. 

Figure 9 shows a schematic process of biodiesel production by the two-step supercritical methanol method. Several advantages have been attributed to the two-step reaction method. At temperature of 270°C, a common type of 316 stainless steel can fulfill the requirements of good corrosion resistance and cover the reaction condition (5). Energy requirements may be less because mild reaction conditions for hydrolysis and methyl esterification are employed, whereas high-temperature treatment causes operational and equipment problems with, in some cases, the formation of undesirable degradation products. In addition, a reaction temperature of 270°C is commonly used in industries, so such a reaction condition is applicable for commercial applications. 

Fatty acid mono-ester diesel fuel (or biodiesel) has advantage over petroleum-based fuel in being a renewable source of energy, virtually free of sulfur and aromatic compounds (Bagley et al., 1998). Biodiesel fuel reduces total particle volume concentration and does not increase any of the potentially toxic, health related emissions. 

Kiss, A.A., Dimian, A.C., Rothenberg, A., The heterogeneous advantage biodiesel by catalytic reactive distillation, Top. Catal., 40, 141-150, 2006... 

Biodiesel potentially offers environmental advantages over conventional diesel fuel. Most important, it converts waste cooking oil into a useful product, reducing the amount of waste going into landfills and replacing some of the petroleum that must be burned. Also, biodiesel comes from biomass that has been recently synthesized from atmospheric carbon dioxide, so the cycle of its production and use might not add as much carbon dioxide to the atmosphere as does the burning of petroleum-based diesel fuels. 

In spite of its many advantages, performance during cold weather will impact the year-round commercial viability of biodiesel in moderate temperature climates. Field trials have demonstrated that methyl esters of soybean oil fatty acids (SME) cause performance issues when ambient temperatures approach 0°C. As overnight temperatures decrease into this range, saturated fatty acid methyl esters (FAME) within SME solidify and form crystals that plug or restrict flow through fuel lines and filters. 

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