Thinking Through Years Ahead

Biodiesel Production

Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid similar in composition to mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. 1 part glycerol is produced for every 10 parts biodiesel.

Biodiesel is made by chemically altering an organic oil (typically vegetable oil) through a process called "transesterification". Essentially, the process thins down the oil to allow it to run in an unmodified diesel engine.

In organic chemistry, transesterification is the process of exchanging the alkoxy group of an ester compound by another alcohol. These reactions are often catalyzed by the addition of an acid or base.


Transesterification: alcohol + ester → different alcohol + different ester


Production Process

Filtering and Heating

Oil is filtered to remove dirt, and other non-oil material. Water is removed because its presence causes the triglycerides to hydrolyze to give salts of the fatty acids instead of undergoing transesterification to give biodiesel.

This is often accomplished by heating the filtered oil to approximately 120 °C. At this point, dissolved or suspended water will boil off. A sample of the cleaned oil is titrated against a standard solution of base in order to determine the concentration of free fatty acids (RCOOH) present in the waste vegetable oil sample. The quantity of base required to neutralize the acid is then calculated.




Transesterification

While adding the base, a slight excess is factored in to provide the catalyst for the transesterification.
The calculated quantity of base (usually sodium hydroxide) is added slowly to the alcohol and it is stirred until it dissolves. Sufficient alcohol is added to make up three full equivalents of the triglyceride, and an excess is added to drive the reaction to completion.

The solution of sodium hydroxide in the alcohol is then added to a warm solution of the waste oil, and the mixture is heated (typically 50 °C) for several hours (4 to 8 typically) to allow the transesterification to proceed.

Used oil (straight vegetable oil) recycling requires titration. We do a titration to find out how much free fatty acid is present and to find out how much to compensate for it by adding more lye so there's some left for the desired biodiesel reaction.The biodiesel reaction needs alkaline lye (NaOH) or KOH, as a catalyst (methanol and vegetable oil wont' react to make biodiesel by themselves) Waste oil contains free fatty acids (FFA), and the free fatty acids will with lye to make soap before the lye has a chance to participate in making biodiesel.

Washing

There are a number of water-soluble impurities left in biodiesel after the reaction and initial settling is complete.. Biodiesel should be washed to remove the excess catalyst, alcohol and other impurities.When Biodiesel is first made it is quite caustic with a pH of between 8.0 and 9.0.

Washing with plain water is sufficient to wash out all remaining catalyst, bringing the pH down to near neutral territory. Since Biodiesel has a lower specific gravity than water, the water will sink to the bottom and the Biodiesel will remain over the water.

In the first wash, the water will turn almost totally white. This is because a form of soap is created when water comes in contact with the catalyst in the Biodiesel. It should clear up as the soap washes out with sub sequent washings.

http://www.biodieselcommunity.org/

Thinking Through Years Ahead

Biofuels

Biofuels are any kind of fuel made from living things, or from the waste they produce. Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants. Many different plants and plant-derived materials are used for biofuel manufacture. The two most prevalent biofuels are ethanol, currently produced from sugar or starch crops, and biodiesel, produced from vegetable oils or animal fats Biodiesel was probably the first of the alternative fuels to really become known to the public. Ethanol for fuel is made through fermentation, the same process which produces it in wine and beer.

Plants absorb carbon dioxide as they grow which is released when biofuels are burnt. .Some additional energy is required to grow and process biofuels but the net carbon dioxide emitted is less than the alternative of burning fossil fuels. The great advantage of biodiesel is that it can be used in existing vehicles with little or no adaptation necessary.

With near record oil prices, the future of biofuel—made from plant material—is of keen interest worldwide. Global biofuel production has tripled from 4.8 billion gallons in 2000 to about 16.0 billion in 2007, but still accounts for less than 3 percent of the global transportation fuel supply.

Biofuels are essentially a way to convert solar energy into liquid form via photosynthesis. One of the greatest concerns raised about them, however, is their net energy balance—i.e., whether production of the fuels requires more energy inputs (particularly fossil energy, in the form of fertilizers, tractor fuel, processing energy, etc.) than is ultimately contained in the biofuels themselves. Advances in technology have improved production efficiency, giving all current biofuels a positive fossil energy balance.

Gas combustion engines running on Bioethanol, which is produced from agricultural crops, sugar cane or bio-mass, burn basically the same as gasoline. They both emit CO2 during combustion. But the burning of ethanol recycles the CO2 because it has already been removed from the atmosphere by photosynthesis during the natural growth process. In contrast, the use of gasoline or diesel injects quantities of CO2.