Year 12 Chemistry: Chemistry: Chapter 11 Biochemical Biochemical fuels 11.1 Fossil Fuels Coal is used to generate ______________ . Crude oil, such as petrol and diesel are used to ____________ vehicles. It can also be used to manufacture plastics and pharmaceuticals. pharmaceuticals. Peak oil ‘Peak oil’ is the time when worldwide oil extraction is no longer able to keep up with increasing demands.
he actual timing of ‘peak oil’ is debatable. !e ma" actuall" be there now### he situation provides motivation to devise renewable and sustainable sources of the carbon compounds. 11.2 Biochemical fuels !e are making enormous demands on the planet in terms of providing sufficient fuel resource.
here is increased motivation to ensure that the new sources of energ" are$ Clean % produce much less pollution &reen % come from renewable and sustainable sources Biochemical fuels 'biofuels( are fuels derived from plant materials such as grains 'mai)e, wheat, barle" or sorghum(, sugarcane and vegetable waste and vegetable oils. he two main biofuels are$ *thanol +iodiesel he" are used either alone or blended with fossil fuels such as petrol and diesel.
+iochemical fuels are not considered to contribute to an increase in atmospheric carbon dioxide. he plant materials used in the generation of biochemical fuels are produced b" photos"nthesis, which removes carbon dioide from the atmosphere and produces glucose$
Plants then convert the glucose to starch and cellulose 'pol"saccharides(. he carbon dioide is then released when the biochemical fuel is burnt. +iochemical fuels are therefore considered to be carbon neutral.
!thanol umans have emplo"ed the en)"mes in "easts to convert starches and sugars to ethanol. *n)"mes are used to catal"se the breakdown of the pol"saccharides starch in grain to glucose, and then the fermentation process uses other en)"mes from "east organisms to convert small sugar molecules such as glucose to ethanol and carbon dioxide$
his is an anaerobic process % it takes place in the absence of ox"gen.
he fermentation stops when the ethanol content is between - to /0, at which point that "easts and their en)"mes no longer function. It is then pumped to an evaporation plant where steam is added to cause the 'lower boiling point( ethanol to evaporate off. !hen cooled, the li1uid now contains about 230 ethanol and 30 water. his is deh"drated 'water removed( leaving ethanol that is 22.40 pure. In 5ustralia, the final ethanol is then ‘denatured’ b" adding up to 30 petrol to make it unsuitable for consumption as drinking alcohol.
Care is taken to avoid wast and pollution$ Carbon dioxide produced in the fermentation step can be sold to manufacturers of carbonated drinks. he waste water and cooling water can be used for irrigating crops he protein6rich remains from the fermentation can be sold as animal feed.
he cellulose found in biomass such as wood" plants can also serve as a raw material for ethanol production. &eneticall" engineered *.coli bacteria have been developed that convert the pol"saccharides in materials like forestr" waste, corn stalks and sugarcane residue into ethanol. In 5ustralia petrol containing -0 ethanol is known as *-. Biodiesel Biodiesel is a mix of esters produced b" chemical reaction between vegetable oil and an alcohol such as methanol.
It is possible to run diesel vehicles on -0 ester fuel. he usual raw material is fresh vegetable oil from sources such as so"bean, canola or palm oil, but rec"cled vegetable oil or animal fats can also be used. 7ats and oils are tri"lycerides 'Chapter -/(.
he trigl"ceride is hydrolysed 'water added( b" warming it with methanol and potassium h"droxide solution 'catal"st(. he trigl"cerides breaks down into three ‘ fatty acid’ molecules, plus gl"cerol. #ydrolysis $eaction of a tri"lyceride
he fatt" acid then reacts with methanol to form the ester$
he esters produced are less viscous than vegetable oil. !hen burnt the" release a similar amount of energ" to petrodiesel. +iodiesel can be used in a mixture with petroldiesel and is known as +3 and +- '30 and -0 of biodiesel(. +iodiesel is biodegradable, non6toxic and produces fewer pollutants in the vehicles emissions. 5lso it is not adding to the overall amount of carbon dioxide in the atmosphere as it is simpl" rec"cling the carbo dioxide alread" present rather than releasing carbon stored in fossil fuels. here have been some feasibilit" studies on the production of oil for biodiesel from algae. Bio"as +iogas consists mainl" of carbon dioxide and methane in roughl" e1ual 1uantities and is generated when organic materials deca"s in the absence of ox"gen. It can be used for heating to power homes and farms. he waste from biogas generator can be used as a rich fertiliser.
8our local rubbish tip has the potential to suppl" biogas. %hy develop biochemicals &ases such as water vapour and carbon dioxide absorb heat energ" from the 9un and act as a sort of ‘blanket’ to trap the heat in the atmosphere. :ife on *arth could not survive without this greenhouse effect, but the enormous additional amount of carbon dioxide produced b" burning fossil fuels is causing further heating effects. !hich is believed to be triggering conse1uential shifts in weather patterns and climate. 9ome plant and animal species have alread" been driven into extinction.
5lthough the combustion of biochemical fuels produces carbon dioxide, the" are produced from plant materials made b" photos"nthesis, which consumes an e1ual amount of carbon dioxide % carbon neutral.
Production of bio ethanol at present generall" uses water material left over after food production. he production of ethanol uses resources that are available in 5ustralia. his means that production in 5ustralia is unlikel" to be influenced b" problems in importing raw materials. It also provides emplo"ment at man" different levels. $udolf &iesel: the earliest "reenie' In the "ears ;ust before his death in -2-< he stated$ ‘he diesel engine can be fed with vegetable oils and would help considerable in the development of agricultural of the countries which use it’. (uestions: /, =, --, -/, <, 4, >, ?, 2, ->. $ead: Please ensure "ou read the chapter as I did leave out interesting information.
