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Biodiesel - Coggle Diagram
Biodiesel
Extraction techniques
Enzymatic extraction: the use of enzymes to digest the cellular membranes of seeds. Applications of enzymes like cellulases and proteases to digest the cell walls of the seeds. Oil is then extracted using centrifugation or filtration. Adv: no chemical use, environmentally friendly process, quality can actually improve. Dis: enzymes may increase costs, special equipment>costs, relatively slow process.
Microwave extraction: the use of a special microwave apparatus to heat oil containing seeds. Oil is then collected through centrifugation or filtration. Adv: uses less energy produces less waste. Dis: results in oil of lower quality than mechanical pressing, use of special equipment>costs.
Soxhlet extraction: involves the use of the soxhlet extractor apparatus. Solvent is placed the thimble, followed by addition of the seeds. The solvent is heated, then cooled in the cooling chamber. Solvent falls back down on the seeds. Oil mixed with the solvent is then collected. Adv: efficient and convenient. Dis: use of special equipment increases the costs, further processing is required to separate solvent from the oil, the use of a solvent/chemical- may result in toxic by products, oil-free cake (disposal challenges).
Supercritical fluid extraction: use of a supercritical fluid such as CO2 as a solvent to extract oil from seeds. After passing through a separator, oil-rich CO2 is captured and reused. Adv: may result in oil of higher quality, does not release harmful products or pollutants. Dis: sophisticated equipment>costs, may take longer than alternatives.
Mechanical pressing: the use of a hydraulic press or screw press to apply pressure on non-edible oil seeds, to obtain oil. Oil containing seeds are placed in a cylindrical chamber and subjected to pressure. Adv: les energy use, no chemical use, high-yield, enviro-friendly, results in oil of higher grade quality. Dis: lengthy process, pressure limitations, oil-free cake waste (hard to get rid of)
Solvent extraction: use of a solvents like hexane to extract oil. Oils are subjected to a solvent in order to remove oil from them. Adv: larger yield of oil is produced, process is quicker than alternatives. Dis: can be toxic>> solvent may generate harmful waste and fumes, cost of solvent, process may degrade oil quality (damage and leaving behind trace amounts of the solvent)
Ways to produce biodiesel
Transesterification: Fatty acid methyl etsers and glycerol are produced when triglycerides and an alcohol such as methanol are combined in the presence of a catalyst., between 60-80C. Adv: well-established technique, easy to carry out, economical nature, versatile.
Esterification: the production of an ester from a carboxylic acid and an alcohol.
Pryolysis: aka thermal cracking. chemical change due to the application of thermal energy in the presence of a catalyst and in the absence of air or nitrogen. Adv: full oil feedstock utilisation.
Blending: non-edible oil can be blended with regular diesel, the resulting oil can be used directly as fuel for a car engine.
Micro-emulsification: the use of surfactants or polar solvents (e.g., methanol, ethanol, hexanol, etc) to create a thermodynamically stable liquid mixture between oil and water at a nanoscale level. surfactants> surface active agents>>reduce the tension at the interface of water and oil allowing them to mix and form a stable micro-emulsification. Create small enough droplets of oil to dissolve in water. Adv: helps overcome the challenges of high viscosity and atomization properties of biodiesel. (improved atomization, reduced viscosity, lower emissions).
Physical characterisation of biodiesel
Flash point: the lowest temperature at which a liquid, when heated, releases vapours which can ignite when an ignition source (spark or flame) is introduced.
Pour point: the temperature at which biodiesel becomes too thick to pour. Biodiesel has a low pour point.
Density: key physical parameter which influences the usefulness of a biodiesel and how much energy a biodiesel has.
Viscosity: key physical parameter which influences the thickness of biodiesel
Cetane number: a key safety feature which measures ignition quality to asses the efficiency of biodiesel. high cetane number> high ignition quality> less time required for combustion
Burning fats results in enhanced energy bonds than burning carbohydrates.
second gen biodiesel advantages: require less land, water and fertiliser than edible feedstocks, potential to improve rural areas economically, part of a carbon cycle, biodegradable, from a renewable resource, does not result in food insecurity
First gen, produced from edible crops (safflower, sunflower, soybean)
second gen, produced from non-edible crops such Jatropha, neem, royna, karanja, polanga
third gen, produced from algae (microalgae, C.vulgaris)
Biodiesel is a biofuel, introduced as an alternative to petroleum fuels. They are less polluting than petroleum based fuels. CO2 is released but there is no net release (CO2 is recycled).