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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

148 7 Annex In all

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

7.1 Country specific life cycle comparisons 149 higher concentration of mineral nitrogen in fermented manure compared to non-fermented manure. The mineral nitrogen concentration in manure rises due to fermentation. Another reason for acidification is the high NOx emission for combustion of biogas. Eutrophication – The Netherlands g NO3 eq./MJ useful energy 2 1,5 1 0,5 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 eutrophication than the reference system. Hemp has the largest difference in eutrophication compared with the reference system and sugar beet for ETBE the smallest. For Miscanthus the eutrophication score during the energy production part with the fossil reference system is remarkable. This is related with the NOx emissions from combustion (see previous graph). For sugar beet and especially hemp the difference is mainly caused during the agricultural part. This can be explained by the more intensive fertilising for these crops compared with fallow. The difference between biogas and its reference is caused by a higher ammonia volatilisation due to the application of fermented swine manure and a higher NOx emission in the chain of biogas compared with the reference. Compared with the other biofuels, biogas has a larger impact on eutrophication.

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