5 years ago



74 4 Environmental

74 4 Environmental results: presentation, discussion and interpretation 4.4.6 Italy The assessment of the Italian chains under study focused on the following comparisons: • Sunflower oil methyl ester (SME) versus fossil diesel fuel • Firewood versus heating oil and natural gas • Biogas versus natural gas The results can be summarised briefly as follows: it is difficult to identify the best biofuel among those studied since each one has its own characteristics and specific advantages and disadvantages, although firewood seems to be the energy carrier with the highest environmental advantages, thanks to a good performance over light oil in the whole set of impact categories considered. In more detail: • Use of fossil fuels: all biofuels present a better performance than the respective fossil fuels. • Greenhouse effect: all the biofuels under study are better than the respective fossil fuels. This is due to the fact that all the CO2 produced during the combustion of the biofuels is considered to be recycled by the growing crops. • Acidification: all the analysed biofuels are worse than the respective fossil fuels except wood in comparison to light oil. This means that biofuels in general lead to an increase in acidification. • Eutrophication: SME has a very good record with respect of this category due to the system expansion with soy meal which gives a credit in favour of SME. • Summer smog: all biofuels perform differently compared to their respective fossil fuels. The biogas chain has the highest advantage, due to the credits regarding its methane content. Impact category Sunflower (SME) Firewood vs. light oil Firewood vs. nat. gas Biogas Use of fossil fuels + + + + Greenhouse effect + + + + Acidification - + - - Eutrophication + - - - Summer smog - + + + (+) advantage for biofuel; (-) advantage for fossil fuel Two other environmental parameters were studied within this project, even if due to a high uncertainty of their base data the results should be considered with caution (for more information on these parameters see Chapters 3.4 and 4.1.2): • Nitrous oxide: the only biofuel able to decrease the nitrous oxide is firewood for district heating. The biogas chain presents as low N2O emissions as wood, but compared with natural gas the value for this parameter becomes negative. SME performs unfavourably with regard to N2O because of the fertilisation of the sunflower crop. In fact, the agricultural part of the sunflower chain, even if decreased by the agricultural reference system, is characterised by a certain amount of fertiliser that leads to large N2O emissions. • Human toxicity: SME seems to have a little advantage over fossil diesel, firewood versus light oil seems to have a smaller advantage whereas biogas has a negative effect with respect to this impact, but again it should be stressed that the results relevant to this last impact are characterised by a large uncertainty.

4.4 Summary of country specific results 75 4.4.7 The Netherlands Bioenergy chains that have been investigated for The Netherlands are willow and Miscanthus for heat production, hemp for electricity, sugar beet for ETBE (transport) and biogas from pig manure. The environmental analysis leads to the following conclusions: • The amount of useful energy produced (gross energy times efficiency of conversion) by the energy crops investigated range from 125 GJ/ha for ETBE to 212 GJ/ha for Miscanthus. As expected all bioenergy chains use far less primary energy than the fossil reference system and far less greenhouse gases are emitted. This is caused by the use of biomass for the production of biofuel instead of using fossil resources. • Besides that, all biofuels have lower impacts regarding summer smog. Only for Miscanthus the difference between it and the fossil fuel is quite small. This is due to the combustion of Miscanthus which emits relatively more VOC and benzene than other biofuels. • On the other hand all biofuels lead to a larger impact on eutrophication. This is partly caused by an increase in agricultural activities (fertilising) when energy crops are grown compared to fallow land in the reference system. The increased eutrophication in the case of biogas is mainly related to the increase in ammonia volatilisation from fermented manure. • For ozone depletion only nitrous oxide is looked at. All biofuels except biogas cause a higher nitrous oxide emission than the fossil reference system. This is due to fertilising, and for Miscanthus the main reason is the emission from combustion. • For acidification all biofuels cause a higher impact than their fossil counterparts. For hemp and ETBE this is explained by ammonia emission from fertilising. For willow and Miscanthus it is mainly caused by NOx emissions from combustion. Biogas from manure leads to more ammonia volatilisation, which is related to the increased mineral nitrogen content in manure due to fermentation. • For human toxicity, willow and especially Miscanthus (dioxins from combustion) have distinct disadvantages compared to the fossil fuels. The other chains have only a minor disadvantage (hemp, ETBE and biogas). • Environmental issues that have not been included in the analysis – due to methodological or data quality problems – should nevertheless be taken into account. From an earlier study (Biewinga & Van der Bijl 1996, on energy crops in the northern part of The Netherlands) we expect that the impact on ecotoxicity and persistent toxicity from pesticides will only increase significantly when growing sugar beet. Willow, Miscanthus and hemp can be grown with little or no pesticides. The same study expects that the biodiversity – compared with grass fallow – improves when growing Miscanthus. Hemp scores neutral, sugar beet and willow score negative. As The Netherlands are a densely populated country, land use efficiency is important. In the intensive crop rotations in The Netherlands, the space for perennial crops is limited. This limited space can be used for willow or Miscanthus. The choice probably depends on energy production (higher with Miscanthus) and polluting emissions from combustion (lower with willow). Multifunctional land use becomes more and more important in The Netherlands. Therefore biodiversity (better with Miscanthus) and landscape (better with willow, see chapter 5.3) also play an important role. Annual crops, like hemp and sugar beet, fit much better into Dutch arable farming than perennials. In general the results for the annuals sugar beet and hemp go in the same direction, when compared with their fossil counterparts. When implemented in The Netherlands, the relatively high amount of fertilisation of hemp is a point for improvement. On the other hand, the useful energy yield of hemp is higher than from sugar beet. But of course the fuels produced are different: electricity and MTBE respectively. Finally biogas has good perspectives in The Netherlands, because of the high availability of manure. Biogas scores better than natural gas, with exceptions for acidification and eutrophication. Biogas does not compete with energy crops, as no extra land is needed for its production.

Bioenergy Update 10-02 - General*Bioenergy