Biodiesel
Biodiesel is a renewable and biodegradable diesel fuel extracted from plant oil. A natural hydrocarbon with negligible sulfur content, it will substantially help in reducing emissions from diesel-fed engines.
Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel consisting of long-chain alkyl (methyl, propyl or ethyl) esters. Biodiesel is typically made by chemically reacting lipids (e.g., vegetable oil, animal fat (tallow)) with an alcohol. Biodiesel is meant to be used in standard diesel engines and is thus distinct from the vegetable and waste oils used to fuel converted diesel engines. Biodiesel can be used alone, or blended with petrodiesel. Biodiesel can also be used as a low carbon alternative to heating oil.
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[edit] Fats and Biodiesel
Part of what makes biodiesel so appealing and interesting is that it can be made from numerous natural sources. Although animal fat can be used, plant oil is the largest source of biodiesel. Scientists and engineers can use oils from familiar crops such as soybean, rapeseed, canola, palm, cottonseed, sunflower and peanut to produce biodiesel. Biodiesel can even be made from recycled cooking grease.
The common thread shared by all biodiesel sources is that they all contain fat in some form. Oils are just fats that are liquid at room temperature. These fats, or triacylglycerols (sometimes called triglycerides) are made up of carbon, hydrogen, and oxygen atoms bound together and arranged into a specific pattern. These triacylglycerols are pretty prevalent. In addition to household vegetable oils, they're also in common things like butter and lard.
[edit] Blends
- 100% biodiesel is referred to as B100, while
- 20% biodiesel, 80% petrodiesel is labeled B20
- 5% biodiesel, 95% petrodiesel is labeled B5
- 2% biodiesel, 98% petrodiesel is labeled B2
[edit] Advantages
One of the major selling points of biodiesel is that it is environmentally friendly. Biodiesel has fewer emissions than standard diesel, is biodegradable, and is a renewable source of energy.
Biodiesel has several key advantages:
- Biodiesel is environmentally friendly.
- It can help reduce dependency on foreign oil.
- It helps to lubricate the engine itself, decreasing engine wear.
- It can be used in almost any diesel with little or no engine modification.
- It is safer than conventional diesel.
Biodiesel does reduce hazardous emissions. Of the current biofuels, biodiesel is the only one to have successfully completed emissions testing in accordance with the Clean Air Act.
Average Biodiesel Emissions Compared to Conventional Diesel
| Emission Component | B100 | B20 |
|---|---|---|
| Total Unburned Hydrocarbons | -67% | -20% |
| Carbon Monoxide | -48% | -12% |
| Particulate Matter | -47% | -12% |
| NOx | +10% | +2% |
| Sulfates | -100% | -20% |
| PAH | -80% | -13% |
Source: National Biodiesel Board
In addition, B100 can reduce CO2 emissions by 78 percent and lower the carcinogenic properties of diesel fuel by 94 percent (National Biodiesel Board, U.S. DOE Office of Transportation Technologies).
Another feature of biodiesel is that it is biodegradable, meaning that it can decompose as the result of natural agents such as bacteria. According to the EPA, biodiesel degrades at a rate four times faster than conventional diesel fuel. This way, in the event of a spill, the cleanup would be easier and the aftermath would not be as frightening. This would also hold true for biodiesel blends.
Biodiesel also contributes to an engine's lubricity, or its ease of movement. Biodiesel acts as a solvent, which helps to loosen deposits and other gunk from the insides of an engine that could potentially cause clogs. Since pure biodiesel leaves no deposits of its own, this results in increased engine life.
Biodiesel is also safer. It is non-toxic (about 10 times less toxic than table salt) and has a higher flashpoint than conventional diesel. Because it burns at a higher temperature, it is less likely to accidentally combust.
[edit] Disadvantages
One of the problems with the fuel itself is the increase in NOx in biodiesel emissions. Often, in diesel fuel manufacturing, when you decrease the amount of particulate matter in the emissions, there is a corresponding increase in nitrogen oxides, which contribute to smog formation.
Biodiesel may contain small but problematic quantities of water. Although it is not miscible with water, it is, like ethanol, hygroscopic (absorbs water from atmospheric moisture). In addition, there may be water that is residual to processing or resulting from storage tank condensation. The presence of water is a problem because:
- Water reduces the heat of combustion of the bulk fuel. This means more smoke, harder starting, less power.
- Water causes corrosion of vital fuel system components: fuel pumps, injector pumps, fuel lines, etc.
- Water & microbes cause the paper element filters in the system to fail (rot), which in turn results in premature failure of the fuel pump due to ingestion of large particles.
- Water freezes to form ice crystals near 0 °C (32 °F). These crystals provide sites for nucleation and accelerate the gelling of the residual fuel.
- Water accelerates the growth of microbe colonies, which can plug up a fuel system. Biodiesel users who have heated fuel tanks therefore face a year-round microbe problem.
- Additionally, water can cause pitting in the pistons on a diesel engine.
[edit] Deforestation
If deforestation, and monoculture farming techniques were used to grow biofuel crops, biodiesel may become a serious threat to the environment:
- Increasing the emission of climate change gases rather than helping curb them
- Damaging ecosystems and biodiversity
- Exacerbating social conflict
The demand for cheap oil from the tropical regions is of rising concern. In order to increase production, the amount of arable land is being expanded at the cost of tropical rainforest.
