The reading lists three alternative fuel to replace traditional petroleum fuel, aiming at
addressing the global warming issue caused by excessive carbon dioxide release. The lectur
e, however, closely examines these options and eventually reaches a conclusion that none o
f these solutions is reliable.Firstly, the reading passage claims that hydrogen fuel cells
can be used on vehicles to provide power. Since these cells involve only hydrogen and oxy
gen in chemical reaction, no carbon dioxide will be emitted to the environment. However, t
he professor directly refutes this idea, saying that hydrogen, the raw material for cells
to function, need to be produced by burning fossil fuels like natural gas. Therefore, duri
ng the process of manufacturing hydrogen, carbon dioxide is released into the atmosphere,
which also contributes to the global warming effect.Secondly, the article put biofuel at t
he candidate position for replacing petroleum. This is because while burning plants materi
als produce carbon dioxide, living plants can absorb it from the air and maintain a balanc
ed level of carbon dioxide in the atmosphere. The lecturer, on the other hand, casts doubt
on this idea. He points out that in order to grow crops to provide enough fuel, twice of
the area of the current farming land in the United States is required, which is simply unr
ealistic since food also need to be cultivated in this country.Thirdly, one exciting techn
ological innovation mentioned in the reading is that today we can extract carbon dioxide f
rom the air and use it as energy. Nevertheless, the speaker argues that currently we can o
nly produce half a liter of fuel per day by applying this method. Despite the fact that ma
ny people are investing their money and time in improving it, it still remains obscure in
the future of this field. At least in current conditions, the energy provided from this te
chnology is far from satisfying the need of energy on a global scale.