between 1st and 2nd generation bioethanol is the source of
feedstock. 1st generation feedstocks are for instance corn,
sugarcane and crops, whereas 2nd generation feedstocks
could be agricultural waste, wood or household waste. Typically,
1st generation feedstocks are based on sucrose or starch
whereas 2nd generation feedstocks are based on lignocellulose and chitin .
Ethanol is produced by fermentation of glucose, which
is readily achieved from the first group of feedstocks through
simple hydrolysis. 2nd generation feedstocks typically consist
of cellulose, hemicelluloses and lignin with the glucose bound
in complex structures and more energy is required to release
the glucose for fermentation. It is important to realize
that the 1st generation feedstocks are also used as food for
humans and animals, which is usually not the case for the
2nd generation feedstocks. The use of 1st generation
bioethanol has led to a vehement debate about the ethical
issues of using food for fuels, see for example reference.
Contrary to 1st generation bioethanol, 2nd generation bioethanol
significantly reduce greenhouse gas emissions from
fuels, thus the use of 2nd generation plants are expected
to increase at the expense of 1st generation bioethanol plants.
Exist also a 3th generation based on algae and