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Carbon Footprint
· Of a fuel = total mass of carbon dioxide produced by a
fuel from production to combustion
· For biofuels, subtract carbon dioxide absorbed in
· Of an organisation = net amount released daily
Carbon Neutrality
· No activity is carbon neutral (except going for a walk)
· Even biofuels are not, as carbon dioxide released before
they are used…read more

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· Should be: abundant, ignite easily, high energy output,
easily transferred to point of use + stored, non-toxic, no
environment damage
· Fossil fuels = mixture of hydrocarbons laid down over
millions of years through anaerobic decay of animal and
vegetable matter
· Gas/oil/coal. For CO2 released per 1000kJ produced,
coal is worst, gas is best. Changing power-stations to
natural gas markedly reduces greenhouse gas
production.…read more

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· Bad: Cannot be liquefied till -83°C, not suitable for
· Good: Found in gas deposits, burns cleanly, can be
piped into houses
· Manufactured from natural gas: CH4 + H2O CO + 3H2
or by electrolysis but this needs electricity
· Derived from fossils fuels so significant carbon footprint,
can only be liquefied at -240°C, explosive, cannot be
stored so not a motor fuel
· However liquid hydrogen best fuel for boosters in rockets…read more

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· In natural gas and produced when oil is cracked. Mixed
with propane, used as domestic fuel + for camping.
Transported in pressurised cylinders. As liquid under
pressure = fuel for vehicles (need to be specially
adapted). Produces less CO2
Other liquid hydrocarbons
· Obtained from crude oil. Easy to transport and transfer as
they are liquids + not volatile. Produce high yield of
energy per mass. However, much more CO2 . If air
supply limited (engines) CO produced (can be removed
by catalytic converter but reduces efficiency).
· Methanol from coal/methane. CO + 2H2 CH2OH
· Highly toxic but great fuel, clean and less CO , more…read more

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· Biofuels = are made from renewable organic materials,
eg. Sugar/grain/vegetable oils
· Bioethanol
· Made by fermentation of carbs. Starch Glucose. Sucrose
Glucose. Enzymes ferment glucose Dilute ethanol.
· Atom economy is max 67% and obtained by fractional distillation
· 96& ethanol, 4% water. 63% of petrol energy output (not as energy
· Biodiesel
· Vegetable oil + methanol (+acid catalyst) =
TRANSESTERIFICATION reaction. Produces methyl ester. Have
similar combustion properties as diesel from petrol.
· Vegetable oil from crops/restaurants and oil from algae.
· Problem with growth = use land that could be food production…read more

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