Biodiesel environmental considerations

The ability to obtain the materials of interest for the maintenance and extension of human society is perhaps one of the most important unsolved problems of the twenty-first century. As one looks around, it is obvious that very few chemicals used routinely in commercial operations are currently available from renewable sources. Occasionally we may find an example of a material that is from renewable sources, but these are usually accompanied by considerable life cycle environmental impacts. Or, we find that there are undesirable trade-offs between environmental impacts, such as a reduction in global warming potential, which at the same time significantly increases the eutrophication potentials associated with the material. A very relevant example of this sort of trade-off is seen in the production of bioethanol or biodiesel, where considerable controversy surrounds the sustainability of both of these fuels. 

Diesel Type III or higher will have very low sulfur levels less than 3 ppm is the target in Diesel Type IV. Reducing the sulfur level is needed to comply with strict environmental requirements, and it not only improves engine life, but comes with considerable reduction in Particulate Matter emission, especially when combined with diesel after-treatment (NOx absorbers, particulate matter filters). FAME normally doesn t add extra sulfur. Addition of 2% biodiesel to low sulfur fossil diesel normally brings back the required lubricity... 

The production of methyl soyate for environmentally friendly solvents and for biodiesel fuel (in the USA) is becoming a significant outlet for soy oil in non-food applications. Further progress in the demand for soy biodiesel will result in additional soybean meal supphes, which will considerably increase soy meal competitiveness as feedstock for hvestock farming and aquaculture. 

The share of the agrarian upstream processes allocated to biodiesel production is reduced considerably to 1.2 % when price allocation is applied compared to 32 % with mass allocation. The lion s share of the upstream environmental burden is then allocated to the main product meat (see Table II). 

The comparison of the two different impact assessment methods is made on the basis of Scenario I, the production of biodiesel from waste cooking oil without the consideration of substitution processes. Since SPI and CML results cannot be directly compared the main focus of investigation is to discuss if both methods point to the same environmental problems arising over the life cycle and identifying the process steps contributing most prominently to the ecological impact. 

Biodiesel is an alternative to petroleum-based diesel fuel and is most often produced from vegetable oils via an acid- or base-catalyzed process. To be viable, in recent years, a considerable attention has been focused on developing environmentally benign and economically feasible processes to produce alkyl fatty acid methyl esters. Such a process requires to reduce the free fatty acid content to an acceptable level (> 1 wt%) and the ttansesterification of glycerides to fatty acid methyl esters. 

Numerous types of basic heterogeneous catalysts, such as alkahne earth metal oxide, anion exchange resins and alkali metal compounds supported on alumina or zeolite can catalyze various chemical reactions such as isomerization, aldol, Michael, and Knoevenagel condensation, oxidation and transesterification [1], Today considerable attention is devoted to the production of biodiesel (FAMEs) as an alternative for petroleum-derived diesel fuel. Biodiesel is synthesized by direct transesterification of vegetable oil or animal fat with a short-chain alcohol, viz. methanol, ethanol, and isopropanol in presence of an acid, base or enzymatic catalyst [2], Considering the advantages of solid base catalysts, for easy separation and recovery, reduced corrosion and environmental acceptance [1], many studies have been conducted on basic heterogeneous catalysts development for biodiesel production [3-13],... 

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