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What is Biofuel?
Biorganic fuel - biofuel - is any combustible plant or animal material that can be used as an energy source. The simplest biofuel is wood; wood-burning as a heat and light source has been popular for millennia. Other common biofuels are made from corn, sugar cane, soybeans, algae, vegetable oils, and even manure
Primary Advantages of Biofuels
Disadvantages of Biofuels
What is Biodiesel?
Alternative fuel for diesel engines
Made from vegetable oil or animal fat
Meets health effect testing
Lower emissions, High flash point (>300F), Safer
Biodegradable, Essentially non-toxic.
Chemically, biodiesel molecules are mono-alkyl esters produced usually from triglyceride esters
Biodiesel can be used in existing Diesel Engines
Pure Biodiesel (B100) or blended with petroleum diesel (B20, BXX).
Rudolf Diesel: peanut oil.
Little or no engine modifications
Use existing fuel distribution network.
Available now
Environmental Issues
Burning fossil fuels increases atmospheric levels of carbon dioxide
Fossil fuels are a
finite resource
Relative Greenhouse Gas Emissions
Biodiesel Samples
Chemistry of Triglycerides
Biodiesel is made from the combination of a triglyceride with a monohydroxy alcohol (i.e. methanol, ethanol…).
What is a triglyceride? Made from a combination of glycerol and three fatty acids:
Transesterification
While actually a multi-step process, the overall reaction looks like this:
CH2OOR1 catalyst CH2OH
| â |
CHOOR2 + 3CH3OH ó 3CH3OORx + CHOH
| |
CH2OOR3 CH2OH
Triglyceride 3 Methanols Biodiesel Glycerin
R1, R2, and R3 are fatty acid alkyl groups (could be different, or the same), and depend on the type of oil. The fatty acids involved determine the final properties of the biodiesel (cetane number, cold flow properties, etc.)
Individual step of Transesterification
First step, triglyceride turned into diglyceride, methoxide (minus Na) joins freed FA to make biodiesel, Na joins OH from water (from methoxide formation) to make NaOH. Other H joins the diglyceride.
H O H
| | |
HCOR1 H HCO H O
| | | | |
HCOOR2 + HCONa +H2O ó CHOOR2 + HCOR1 + NaOH
| | | |
HCOR3 H HCOR3 H
| | | |
H O H O
Triglyceride + Methoxide + H2O ó Diglyceride + Biodiesel + NaOH
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