Alternative Fuels
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what other two problems come to mind when relying on the combustion of alkanes for energy, other than pollution
• the depletion of natural resources - global warming and climate change
what is the name given to new fuels being created that are an alternative to fossil fuels
biofuels
why are these fuels called biofuels
• because they are obtained from living matter that has died recently • rather than millions of years ago
what is the most common biofuel that is and always has been used and why is ti considered one
• wood - it is one because it can be grown quickly (at least a lot quicker than millions of years)
what are examples of non-renewable sources of energy
• the fossil fuels - like coal, gas, and crude oil
what are examples of renewable sources of energy
• biofuels - but also sunlight, wind, tidal or geothermal
what does it mean if a source of fuel is completely carbon neutral
• it uses or absorbs the same amount of carbon dioxide it produces when turned into fuel • meaning the net amount of carbon dioxide released by that fuel is 0
what is an advantage of using biofuels rather then fossil fuels when it comes to carbon neutrality
• biofuels are a lot more carbon neutral than fossil fuels • meaning they produce less CO2 • and therefore contribute less to climate change
why are biofuels more carbon neutral
• when some form of vegetation is grown it absorbs CO2 from the atmosphere (photosynthesis) • however when it is burned and used a fuel it releases some CO2 • although, because it initially absorbs CO2 its net release of CO2 would be less than a fossil fuels • which doesnt absorb CO2 • making it closer to carbon neutral than fossil fuels
where does the carbon dioxide from the air go when absorbed and why does it turn into CO2 again when the plant is burned
• the CO2 from the air is basically split into O2 which is released and C which becomes part of the structure of the plant • when burned, the carbon combusts with the oxygen • forming CO2 again which is released
some fossil fuels are formed from trees. these trees absorbed CO2 when they were alive, so why arent they considered to be carbon neutral to some extent
• the carbon dioxide that they absorbed was from the atmosphere millions of years ago • at this time the amount of CO2 in the atmosphere was much higher • in other words, it doesnt count as the atmospheres were too different for there to be a comparison
what are the two types of biofuels we need to know about
• biodiesel - bioalcohols
although a plant may absorb the same amount of CO2 it releases when it is burned and turned into fuel, why cant it, as a product, still be considered carbon neutral
• because even more CO2 is produced in the process of creating and transporting the fuel • such as harvesting, transporting to a factory, being processed in a factory then being transported to the sale point • all these steps require energy • and so are therefore releasing CO2
where would you find the starting materials for making biodiesel
• vegetable oils - such as those obtained from rapeseed and sunflowers
what is the most common bioalcohol
bioethanol
what was the good old way of producing ethanol
• through fermentation • which involves fermenting sugars into alcohol • you use yeast that contain enzymes to produce it
why is fermentation an ineffective way of producing ethanol
• there is an upper limit to the concentration of the ethanol in the solution (20%) before the yeast die • the ethanol then has to be separated from water using distillation before it can be used a fuel • this separation requires a lot of energy
what actually is bioethanol then
• ethanol produced in a different way - involving bacteria rather than enzymes
what are the advantages of using bacteria rather than yeast containing enzymes for the fermentation
• it is now possible to use a much wider range of plants (sugars) and also plant waste • the upper amount of ethanol that can be obtained from a given amount of starting material is increasing • this is much higher than traditional fermentation
what is the main source of ethanol used in cars made from
corn
why are some people against the use of corn as a source of fuel
because it could be used to feed people insteaed
what are the four main factors of any biofuel that need to be taken into consideration when producing it
• land use • yield • manufacture and transport • carbon neutrality
why does land use need to be considered
• you need to know how much land will be used to grow the crop • should the land be used for other purposes • or even to feed people
why does yield need to be considered
• you need to know how much of a crop can be grown in a given piece of land • and how quickly it grows • you can also think about what percentage of carbon and hydrogen atoms in the crop end up in the fuel