Biodiesel

Biodiesel

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What is biodiesel?

Bio diesel is an alternative fuel that can be used to run conventional diesel engines. It comprises of mono-alkyl esters of long chain fatty acids that are derived from vegetable oils or animal fats. It is an opportunity to improve the environment and is acknowledged as an alternative fuel under the Energy Policy Act of 1992 (EPAct) amended in 1996 (USA) and recognised by Gordon Brown in the 1992 budget (UK) by decreasing the fuel tax on it by 20p per litre when compared to sulphur-free diesel.

Biodiesel is a light to dark yellow liquid. It is practically immiscible with water, has a high boiling point and low vapour pressure. Typical methyl ester biodiesel has a flash point of ~ 150 °C (300 °F), making it rather non-flammable. Biodiesel has a density of ~ 0.86 g/cm³, less than that of water. Biodiesel uncontaminated with starting material can be regarded as non-toxic.

Why not pure vegetable oil?

Pure vegetable oil is too viscous to be used straight in an engine. The use, without modification to the engine, would result in decreased engine life due to increased deposits.

How is vegetable oil transformed into a usable fuel?

There are a number of different processes by which the transformation of pure vegetable oil to biodiesel can take place; this website only looks into one of these, a chemical transformation called transesterification. The vegetable oil is too viscous due to its molecules being built around glycerol, by chemically altering the oil the glycerol can be replaced with something less viscous resulting in a fuel which fits the specifications for a conventional diesel engine. During transesterification the glycerol is replaced by a simple alcohol (ethanol or methanol) to produce an alkyl ester. A catalyst is required for the process to go to completion, a base or acid catalyst can be used which will end up in the glycerol by-product produced from the reaction.

Biodiesel advantages:

·        Saves fossil fuels (one of the most renewable fuels currently available)

·        Utilizes a waste product (if using WVO)

·        Similar energy density to mineral diesel

·        Over 75% reduction in CO₂ emissions

·        Biodegradable

·        96% less hazardous solid waste and 79% less water waste due to production

·        Decrease in toxic organic micro-pollutants

·        Encourages local-scale production (local economies, distribution of wealth)

·        Energy balance of 2.5:1 (energy efficient)

·        High cetane number

·        High flash point (relative to diesel)

·        Reduces potential for military conflict

·        SO₂ emissions virtually eliminated (decrease in acid rain)

·        Non-toxic

·        38% lower hydrocarbon emissions

·        15% lower CO emissions

·        No lead emissions

·        Better lubrication for engine

Biodiesel disadvantages:

• Increased NO emissions
• Freezes at a lower temperature than diesel
• Becomes much more viscous than diesel
• Not compatible with some hoses, gaskets, metals and plastics (forms a sediment as it is a mild solvent).

Health and Safety

Risks involved with the production of biodiesel are; dangerous chemical use, slippery oils, heavy containers, application of heat, and electricity. Ethanol provides the greatest risk as it is a fire and explosion hazard as well as being an irritant.

A full breakdown of the risks involved with all the products used can be found at www.