About a third of the fats and oils made in the USA are animal fats. This includes beef tallow, lard, and chicken fat. Animal fats are attractive raw materials for biodiesel as their price is substantially lower than the price of vegetable oil. This is partly due to the fact that the market for animal fat is much smaller than the market for vegetable oil, since a significant part of the animal fat produced in the US is not estimated to be eatable by humans .
Today, animal fat is added to pet food and animal feed, and is used for industrial purposes, such as the construction of soap. An important part of the domestic animal fat supply is exported.
Animal fats raw materials have the possibility of transforming into high quality biodiesel that meets certain specifications.
How Animal Fats Are Processed
Waste fat from animal carcasses is erased and then converted to oil through a process of subtraction. Processing relies on grinding animal by-products to a fine consistency and cooking until liquid fat separates and pathogens are destroyed. The pavements are mainly passed through a screw press to complete the removal of fat from the solid residue. The cooking process also discards the water, which makes the fat and solid material stable to rancidity. The end products are fat and a high protein food additive known as “meat and bone meal”.
Fatty acid content of animal fats
Animal fats remain fairly saturated, which means that the fat solidifies at a subjectively high temperature. Consequently, biodiesel made from animal fat has a high cloud point (The cloud point is the lowest temperature at which the paraffins or waxes in an oil reach a certain level of turbidity). For example, biodiesel made from beef tallow and lard has a cloud point in the range of 55 ° F to 60 ° F. B100 (pure biodiesel) made from animal fat should only be used in fairly hot climates. However, biodiesel from animal fat can be mixed with diesel oil. In lower blends like B5 (a blend of 5% biodiesel with 95% petro-diesel), the high cloud point of animal fat biodiesel does not have much of an impact on the cloud point of the blend.
Beef tallow and lard typically remain 40% saturated (sum of myristic, palmitic, and stearic acids). Chicken fat is less by around 30-33%. For comparison, soybean oil is 14% saturated and canola oil is only 6% saturated. Consequently, tallow and lard tend to be stiff at room temperature and chicken fat, while still mainly liquid, is quite viscous and almost solid.
High cetane number of biodiesel from animal fat
As a consequence, animal fats raw materials provide biodiesel with a high cetane number, which is a fundamental quality parameter for diesel fuels. Saturated fatty acids are the source of this high cetane number and values better than 60 are common. Soybean oil based biodiesel mainly has a cetane number of around 48-52 and petroleum based diesel fuel is often between 40 and 44. Once animal fat biodiesel is mixed with petroleum diesel, this index High cetane levels can help the engine start faster and run more quietly.
Reduce nitrous oxide emissions from biodiesel from animal fats
One of the important attributes of biodiesel is that it reduces the levels of harmful pollutants in the exhaust of diesel engines, such as nitrogen oxides (NOx), which are involved in the formation of ozone and smog. (Photochemical smog is called air pollution, mainly in urban areas. Ozone is an oxidizing and toxic gas that can cause respiratory problems in humans.)
Biodiesel from animal fats has been shown to tend to produce a minor increase in NOx and, in some cases, no increase (McCormick et al., 2001). The main reason for this is probably that animal fat biodiesel has a high cetane number (> 60) compared to vegetable oil biodiesel (48 to 55). A higher cetane number is known to reduce NOx by lowering temperatures during the initial critical part of the combustion process.
McCormick, RL, MS Graboski, TL Alleman, AM Herring y KS Tyson, “Impacto del material de origen del biodiesel y la estructura química en las emisiones de contaminantes de criterio de un motor de servicio pesado”, Environ. Sci. Technol. V. 35, núm. 9, págs. 1742-1747, 2001.
Stuckey, Ben N. (1972) “Antioxidants as Food Stabilizers”, en Handbook of Food Additives 2ª edición, ed. Thomas Furia. Cleveland, OH: CRC Press.
Tat, ME, J. Van Gerpen y PS Wang, “Efectos de las propiedades del combustible en el tiempo de inyección, el tiempo de encendido y las emisiones de óxidos de nitrógeno para motores alimentados con biodiésel”, ASABE Transactions, V. 50, No. 4, págs. 1123 -1128, 2007.