BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

148 7 Annex
In all studied chains, the biofuel chains cause less impact on the greenhouse warming effect than the
fossil fuel chains. Clearly this relates to the difference in use of primary fossil energy (see previous
diagram). Another important issue which affects the results is the amount of useful energy per ha produced
by each energy crop, because a high production of useful energy per ha can result in a high saving
of CO2 emission. For the different energy crops the following useful energy productions per ha have
been determined: ETBE 125 GJ/ha, Miscanthus 212 GJ/ha, willow 140 GJ/ha and hemp 197 GJ/ha.
For biogas the difference between the emission of CO2 equivalents for the biofuel and the fossil
fuel system is the biggest of all studied biofuels. This significant difference is mainly caused by the
difference in emission of CH4 in the biofuel and reference system. In the biofuel system we assumed
that all CH4 formed in the manure was used in the fermentation process to produce biogas. For the reference
system we assumed that all CH4 formed due to spontaneous fermentation was emitted to air.
This has a large effect as the greenhouse effect of CH4 is 8 times the effect of CO2 (with a 500 year time
horizon, 25 with a 100 year time horizon).
The agricultural part of the bioenergy chains results in a higher emission of global warming pollutants
than the fallow land in the fossil fuel chains. The reason for this is the more intensive use of the
land in the bioenergy chains.
The difference in impact on the greenhouse effect for the four energy crops compared with the accompanying
fossil fuels is about the same. Only for hemp the difference is smaller. This is partly due to
a more intensive use of the land compared with the perennials willow and Miscanthus.
Acidification – The Netherlands
g SO2 eq./MJ useful energy
1,4
1,2
1
0,8
0,6
0,4
0,2
0
willow heat natural gas
heat
Miscanthus
heat
natural gas
heat
Processing & utilisation
Agriculture/forestry part
Fossil fuel life cycle
Agricultural reference system
hemp
electricity
natural gas
electricity
sugar beet
ETBE
transport
MTBE
transport
biogas
electricity +
heat
natural gas
electricity +
heat
All biofuels cause a higher effect on acidification than the fossil fuels. For the energy crops this is
mainly or partly due to a bigger effect on acidification during the agricultural part. This can be explained
by the more intensive fertilisation for these crops compared with fallow, and its accompanying
emission of ammonia.
The results of Miscanthus show an obvious higher effect on acidification due to the energy production
part compared to the energy production part of natural gas. This is partly explained by a 3 times
higher NOx emission during the combustion of Miscanthus. The large difference in effect on acidification
between biogas and its reference can be explained by a higher volatilisation of ammonia during
spreading of the fermented manure compared with non-fermented manure. The reason for this is the