Biofuels Flashcards
Recognise examples of fuels from biomass
- alcohol
- biogas
- wood
Explain how plants produce biomass
Biogas is mainly methane and it is produced from animal and plant waste in digesters
Understand why biogas (mainly methane) is an
important energy resource in certain remote parts of
the world lacking a mains electricity supply or mains
sewage system
They can produce biogas from human sewage, which solves the problem of safe sewage disposal in remote places
where does the rotting of organic material such as
dead plants and animal waste occur?
in marshes, septic tanks and animal digestive systems
what does the rotting of organic material such as
dead plants and animal waste produce?
a mixture of gases including methane
how is the rotting of organic material such as
dead plants and animal waste caused?
by the action of bacteria
how can biogas be produced?
on a large scale using a digester
Explain why methane being released from landfill
sites is dangerous
it can burn or explode preventing use of the site for many years
how is alcohol made?
from yeast
what can alcohol be used as?
a biofuel by mixing with petrol
what is a mixture of petrol and alcohol called?
gasohol
what is gasohol used as?
for cars in countries such as Brazil
Describe the advantages of using biofuels
- alternative sources to fossil fuels
• no increase in greenhouse gas levels
• no particulates produced
what does biogas contain?
- mainly methane
• some carbon dioxide
• traces of hydrogen, nitrogen and hydrogen
sulfide
Describe the uses of biogas
• burning to generate electricity
• burning to produce hot water and steam for
heating systems
• used as a fuel for vehicles
Describe different methods of transferring energy
from biomass
- burning fast growing trees
* fermenting biomass using bacteria or yeast
Describe how methane can be produced on a large
scale using a continuous flow method of providing
organic waste and removing the gas and remaining
solids
it can be made on a large scale using a continuous-flow method in a digester. Organic material is added daily and the biogas is siphoned off and stored. The remaining solid sludge can be used as fertiliser for crops.
Explain why the burning of biofuels does not cause a
net increase in greenhouse gas levels
• if they are burnt at the same rate as the biomass is
being produced
• if areas of land are not cleared of other vegetation
in order to grow crops for biofuels
what does the use of large areas of land result in?
habitat loss, extinction of species and the loss of previous food-growing fields
what does it mean if biogas containing more than 50%
methane is burnt? But what happens when it contains 10%?
incan be burnt in a controlled way but a lower percentage of about 10% is explosive
what is biogas in comparison to other fuels?
is a ‘cleaner’ fuel than diesel and petrol but does not contain as much energy as natural gas
Understand why gasohol is more economically viable
in countries that have ample sugar cane and small oil
reserves
it is used more in countries that have large sugar cane reserves, but low crude oil reserves. In these circumstances the production of gasohol is financially attractive.
Explain why biogas production is affected by
temperature
- low temperatures = decomposer bacteria reproduce and respire slowly so very little biogas is released
- above 45 degrees C = enzymes in bacteria are denatured and the bacteria are killed
Describe why biogas production is affected by
temperature
- low temperatures = little biogas released
- above 45 degrees C no biogas is released
