Biodiesel

1.Issue in brief

Biodiesel is a non-toxic, carbon neutral, biodegradable, and renewable fuel free of sulphur and aromatics that can be used in diesel engines with little or no modification. Biodiesel is generally referred to methyl esters and can be produced from a variety of vegetable oils.

Biodiesel Advantages

  • Environmental - Biodiesel has much lower life cycle CO2 emissions than petrodiesel as well as it contains zero sulphur, no aromatics and generally lower particulate emissions. Moreover, it is biodegradable and non-toxic.

  • Performance - The high flash point of biodiesel improves the safety during fuel handling as well as its high cetane number reduces ignition delay and combustion noise. Furthermore, in blends with low-sulphur diesel biodiesel acts as a lubrication improver and is used as an ignition improver in 100% bioethanol engines. In addition, it can be used without problems in standard diesel engines in blends up to 5% with conventional diesel fuel, and in some engine makes in blends of 30-100%. Finally, it can use waste oils as raw material.

Biodiesel Disadvantages

For biodiesel, the only environmental disadvantage is the higher nitrous oxides (NOx) emissions.
Biodiesel has been around for over a century; in fact the diesel engine was originally designed by Dr. Rudolf Diesel to run on vegetable oil. At the World Exhibition in Paris in 1900, when the diesel engine was first demonstrated to the world, his engine was running on a fuel derived from peanut oil.

Prior to his death in 1913 he stated that; "The diesel engine can be fed with vegetable oils and would help considerably in the development of agriculture of the countries which use it." and "The use of vegetable oils for engine fuels may seem insignificant today. But such oils may become in course of time as important as petroleum and the coal tar products of the present time." However due to the low cost of mineral oils at the time his engine was modified to run such oils.

3. Current Best Practice

The production of biofuels worldwide is increasing sharply. The United States, Brazil and Europe account for most of this growth.

During the last years various regulations have come into force for the promotion of biofuels or other renewable fuels which vary greatly from one geographic area to the next. All countries are obligded to set up indicative substitution targets till 2010 but there might also be some differences in the year according to the country.

The main measure that has been taken, varied as well from one country to another, and aims to promote the use of biofuels is the favorable tax measures which have had a major impact on motor fuels, via full or partial tax relief, as well as on agricultural policy.

4. Areas of Research

Some of the crops that present a good potential for producing biodiesel are the oilseed rape (Brassica napus ssp. oleifera), sunflower (Helianthus annuus), caper spurge (Euphorbia lathyris), ethiopian mustard (Brassica carinata), soybean and palm. In Europe biodiesel is commonly derived from rapeseed and sunflower oil. In developing countries there is currently great interest in Jatropha.

Biodiesel is applied in various blends dependently on the amount of biodiesel, which has been mixed with the road diesel. Pure bodiesel as it derives from the transesterification reaction is called B100. Moreover there are B2 which means 2% biodiesel and 98% petroleum diesel, B5 (5%biodiesel and 95% petroleum diesel), B10, B20, B50, B95 and B99. The 100% biodiesel (B100) is mostly used in some countries in Europe, especially in Germany, while B5 to B20 are used successfully throughout United States, Canada and Europe. To date, the fuel is used mainly as a diesel blend, typically 5% or 20%. For higher blends, modifications in vehicle engines may be required.

Biodiesel Conversion Process

Biodiesel is produced from vegetable oil extracted from seeds using a screw press or similar device. The oil then reacts with alcohol (usually methanol, but ethanol can be used) in a catalytic process where the catalyst is usually potassium hydroxide (KOH) or sodium hydroxide (NaOH).

Firstly, methanol is mixed with catalyst, which is either KOH or NaOH in a reactor vessel. Especially KOH can be diluted in methanol in 1% wt of the oil amount. The mixture (methanol/catalyst) with the vegetable oil are then driven to a reactor in order the reaction to be carried out.
This catalytic process results in the formation of esters of the long chain fatty acids from the oil and provides glycerol as by-product (a valuable by-product used in soaps and other products). Basically, the large molecule structures (triglycerides) are transformed into smaller chains (methyl esters) similar to fossil diesel. This process is called transesterification.

More specifically, methyl ester (biodiesel) and glycerine are the obtained products from the reaction that are afterwards separated in order to be handled as two products. The methyl ester, after being separated from glycerine, is purified with water, because of traces from the catalyst or glycerine. Moreover, biodiesel is drying in order to obtain a 98% purified product that can be further enhanced by distillation processes. The end product has a yellow colour with reduced viscosity and better performance in diesel engines.

Although few countries have started to conduct research for the further treatment of glycerine, it is a by-product that can be used in a wide range of existing markets, having many end uses. Some of the uses are in the pharmaceutical and cosmetics industry, tobacco industry, food industry and other miscellaneous uses throughout industry. Glycerine is derived from a number of industrial processes. Fatty acid production and soap production are together responsible for 65% of global glycerine production, with fatty esters and alcohols production, synthetic petrochemical manufacture and biodiesel production accounting for the remaining 35%. Crude glycerine is 70% pure and is usually refined to further points of purity up to 99%.

The production of biodiesel (methyl esters of vegetable oils) is a proven technology, with production capacities of several hundred thousand tonnes.

5. Organisations/People

7.Documents for further reading

Contributors

User:Grant Ballard-Tremeer - 25 October 2004
User:Donna Skordili - 27 March 2007




Last edited by Miriam Hansen , based on work by Grant Ballard-Tremeer .
Page last modified on Wednesday 15 of September, 2010 15:52:49 GMT. @HEDON: HJDB

Technologies » Biofuels Continents » Global
History
  • A practitioner's journal on household energy, stoves and poverty reduction.

Latest News

No records to display


Upcoming Events

No records to display

Show php error messages