Fossil Fuels• Most of our energy needs are met by burning

fossil fuels such as coal, petroleum and natural gas.• Coal is used to generate electricity and

products derived from crude oil, such as petrol and diesel are used to transport fuels.• Other products derived from crude oil are

used to manufacture a range of products, from plastics to pharmaceuticals.• There are large reserves of coal, however,

petroleum deposits are limited.

Peak Oil• Is the time when worldwide oil extraction can

no longer keep up with increasing demand.• The greatest amount of oil discovered was in

1964, and since then new reserves found have gone down in size each year.• However, demand for oil has increased.• The situation provides motivation to devise

renewable and sustainable sources of the carbon compounds, both for fuels and to provide feedback for the organic chemical industry.

Biochemical Fuels• Biochemical fuels, biofuels, are fuels derived from plant

materials such as grains, sugarcane or vegetable waste and vegetable oils.

• The two main biofuels are ethanol and biodiesel.• They are used either alone or blended with fossil fuels such

as petrol or diesel.• Biochemical fuels are not considered to contribute to an

increase in atmospheric carbon dioxide.• The plant materials used in the generation of biochemical

fuels are produced by photosynthesis, which removes carbon dioxide from the atmosphere and produces glucose.

• The plant converts the glucose into cellulose and starch.• The carbon dioxide is then released when the biochemical

fuel is burned.• Biochemical fuels are considered as carbon neutral.

Ethanol• Enzymes are used to catalyse the breakdown of the

polysaccharide starch in grains to glucose and the the fermentation process uses other enzymes from yeast organisms to convert small sugar molecules such as glucose to ethanol and carbon dioxide.

• This is an anaerobic process, meaning it takes place without oxygen.

• The fermentation stops when the ethanol content is between 10 and 20%, at which point the yeasts and their enzymes can no longer function.

• The fermented mixture is pumped to an evaporation plant where steam is added to cause the ethanol to evaporate off.

• When cooled, the resulting liquid contains 95% ethanol and 5% water.

• This is dehydrated leaving ethanol that is 99.7% pure.• In Australia, the ethanol is denature (poisoned) by adding up

to 5% petrol to make it unsuitable for consumption as drinking alcohol.

Ethanol – minimising waste• The carbon dioxide produced in the fermentation step can be

sold to manufacturers of carbonated drinks.• The waste water and cooling water can be used for irrigating

crops.• Protein rich remains from the fermentation can be sold as

animal feed.

Ethanol• The yeasts are used to ferment material such as

molasses and grains contain enzymes that act on glucose.• However, the fibrous waste material from sugar

production, called bagasse, is made of a different type of sugar molecule, xylose.• This is a pentose – a sugar that contains five carbons

per molecule, and is not recognised by usual yeasts.• An Australian development has been to selectively

breed yeasts whose enzymes are able to digest the bagasse by product.• The development of these yeasts will greatly increase

the amount of ethanol produced from a given quantity of sugarcane.

Ethanol• The cellulose found in biomass such as woody plants can also

serve as a raw material for ethanol production.• Genetically engineered E. coli bacteria have been developed

that convert the polysaccharides in materials like corn stalks and sugarcane residue into ethanol.

• It also reduces the need to dispose of these waste materials in landfill or by burning.

Ethanol• A process developed in

Canada to convert plant cellulose to glucose.

Biodiesel• Biodiesel is a mix of esters produced by a chemical

reaction between vegetable oil and an alcohol such as methanol.• The chemical and physical properties of the esters in

biodiesel are similar to those of diesel.• The usual raw material is fresh vegetable oil from

sources such as soybeans, canola or palm oil, but recycled vegetable oil or animal fats can also be used.• Fats and oils are triglycerides with a molecular structure

consisting of three hydrocarbon chains attached by ester functional groups to a backbone of three carbon atoms.

Biodiesel• The triglyceride is hydrolysed by warming it with

methanol and potassium hydroxide solution.• The potassium hydroxide solution acts as a catalyst in

this hydrolysis reaction so that overall the triglyceride breaks down to three molecules of fatty acid esters, plus glycerol.

Biodiesel• Ethanol and sodium hydroxide can be used as an alternative

reagents but there are som practical issues involved that make them less useful for large-scale production.

• The esters produced are less viscous than vegetable oil, when burnt they release a similar amount of energy to petrodiesel.

• Biodiesel can also be used in a mixture with petrodiesel; 5% and 10% mixtures of biodiesel in petrodiesel are known as B5 and B10.

• Biodiesel is biodegradable, non-toxic and produces fewer pollutants in the vehicle emissions.

• It is not adding to the overall amount on carbon dioxide in the atmosphere as it is simply recycling the carbon dioxide already present.

Biogas• Biogas consists mainly of carbon dioxide and methane in

roughly equal quantities and is generated when organic material decays in the absence of oxygen.

• Biogas generators are particularly useful for farms as the waste from the generators can be used as a rich fertiliser.

Developing Biochemical Fuels• Our current use of fossil fuels is releasing carbon

into the environment mainly in the form of atmospheric carbon dioxide.• Gases such as water vapour and carbon dioxide

absorb heat energy from the Sun an act as a blanket to trap this heat in the atmosphere.• Life on Earth would not survive without this process,

however, with the increased amount of carbon dioxide there are further temperature increases causing a shift in the climate.• Biochemical fuels are seen as a useful alternative to

the use of fossil fuels.