BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

2.4 Life cycles of liquid biofuels 21
2.4.3 ETBE from sugar beet
Figure 2-7 shows the life cycle of ETBE (ethyl-tertiary-butyl-ether). The corresponding fossil fuel is
MTBE for utilisation in transport vehicles. ETBE is produced from sugar beets. The left hand side of
the diagram shows the various steps of conventional fuel production, whereas the middle column represents
the biofuel chain. On the right hand side processes are shown which are counted as “credits” for
the biofuel system. Thus for example the maintenance of fallow land is no longer necessary, as instead
sugar beet is cultivated. These factors are described in some more detail below.
MTBE production
Winning of
natural gas
Transport
(Pipeline)
MeOH production
MTBE production
(using iso-butene)
and blending
with gasoline
Transport
to end user
Combustion
ETBE production
( sugar beet)
Machines Fuel
Fertiliser Biocides
Cuttings
Agricultural
production
Harvest & transport
Sugar extraction,
fermentation,
dehydration
Transport
ETBE production
(using iso-butene)
and blending
with gasoline
Transport
Combustion
Figure 2-7 Schematic life cycle comparison of ETBE versus MTBE
Details of the life cycle steps
Credits
Fallow
maintenance
Heat production
Heat & pow er
production
Fossil fuel chain: MTBE is produced from oil and natural gas. The crude oil and natural gas are exploited
and transported to Europe, where the oil is refined to produce iso-butene (besides other fuels)
and the gas is used to produce methanol. These two are processed to obtain MTBE, which is blended
with gasoline for combustion in car engines. These assumptions are based on expert judgements and are
considered to represent the marginal technology.
Biofuel chain: The production, application and partial leaching of agrochemicals such as chemical
fertiliser and herbicides are taken into account, assuming good agricultural practice. The use of tractors
for field preparation, sowing, harvest etc. is also included, as is the production and transport of the
seeds. The beets are harvested and transported, while the leaves are left in the field. The sugar is extracted
from the beets and fermented to produce ethanol, which is distilled and dehydrated. The remaining
slop is fermented to give biogas for heat production and the chips are used for heat and power production,
substituting conventional heat and power production. The ethanol is transported to the refinery
and ETBE is produced from this and iso-butene. Finally it is blended with gasoline for combustion in
car engines.
Utilisation: The comparison is based on the utilisation of both types of fuel in a passenger car according
to the EURO-4 emission standard obligatory up from 2005. The reference unit is one kilometre of
distance driven.