46 3 Life cycle assessment of biofuels: methods and tools Concluding Interpretation As with the comparison biofuels versus fossil fuels, no final interpretation was carried out here, other than answering the five questions addressed. But even with regard to these questions, the answers cannot be taken to be absolute. The reason for this is that the term “the most ecological” still depends on the parameters which are given priority. Again, the discussion of the results in Chapter 4 is intended to aid the interpretation of the quantitative data and to enable every decision maker to reach his or her own conclusions on a sound scientific basis.
4 Environmental results: presentation, discussion and interpretation In this chapter the following groups of results are presented: • comparisons between biofuels and fossil fuels investigated on the European level • comparisons between different biofuels regarding special objectives on the European level • country specific life cycle comparisons (summary of Chapter 7.1) • comparisons between the countries for each biofuel (summary of Chapter 7.2) Before the result discussion, in the following introduction information will be given on various aspects of the result presentation. 4.1 Introduction In this chapter the most important definitions documented in the previous chapters are summarised. Furthermore, presentation criteria, the types of sensitivity analyses carried out and the chosen form of result presentation will be explained. 4.1.1 Life cycles under study As explained in Chapter 2, each biofuel investigated was compared to its fossil counterpart by means of complete life cycle analyses. The biofuels under study and their fossil counterparts are listed below. Table 4-1 Life cycle comparisons and the countries that investigated them Life cycle comparison Countries involved Traditional firewood vs. light oil for residential heating Austria, Italy, Switzerland Triticale vs. coal for electricity production Austria, Denmark, France, Germany Miscanthus vs. light oil / natural gas for district heat production Denmark, France, Germany, Netherlands Willow vs. light oil / natural gas for district heat production Denmark, Germany, Netherlands Wheat straw vs. light oil / natural gas for district heat produc- Austria, Denmark, France, Germany, tion Greece Biogas from swine excrements vs. natural gas for combined Austria, Denmark, Greece, Italy, heat and power production Netherlands, Switzerland Rape seed oil methyl ester vs. diesel fuel for transportation Austria, Denmark, France, Germany, Switzerland Sunflower oil methyl ester vs. diesel fuel for transportation France, Greece, Italy ETBE from sugar beet vs. MTBE for transportation France, Germany, Netherlands All intermediate calculations and all result tables regarding the European chains are documented in the external annex. Further information on this can be found in Annex 7.5. 4.1.2 Impacts under study and presentation criteria The environmental impact categories that were considered in the analyses were discussed in the Chapters 3.3 and 3.4. They are listed in Table 4-2. In the presentation of the results the following observations have already been considered: with regard to the parameter greenhouse effect, the differences in the results for the 100 year and 500 year time horizon respectively were smaller than their uncertainties. Therefore only the 500-year values are presented here. The effect of nitrous oxide is uncertain as explained in Chapter 3.4.2, due to the fact that N2O has both ozone depletion as well as ozone forming properties and the net effect is not yet scientifically proven. In the graphs a higher N2O emission is indicated as a disadvantage however.