5 years ago



48 4 Environmental

48 4 Environmental results: presentation, discussion and interpretation The values for the human toxicity category tend to be rather uncertain. The reason for this is that it is extremely difficult to obtain reliable input data (emission and characterisation factors) for all toxicity parameters of relevance. Furthermore, within the scientific community the methodology on the assessment of toxicity is still being discussed. The category biodiversity and soil quality is discussed qualitatively in Chapter 4.2.10 and is not included in the graphs of the following sections since they are extremely difficult to quantify. Table 4-2 Environmental impact categories and data quality Impact category Data quality Use of fossil fuels good data quality; quantitative results presented in the graphs Greenhouse effect good data quality; quantitative results presented in the graphs Acidification medium data quality; quantitative results presented in the graphs Eutrophication medium data quality; quantitative results presented in the graphs Summer smog medium data quality; quantitative results presented in the graphs Nitrous oxide poor data quality; quantitative results presented in the graphs Human toxicity poor data quality; quantitative results presented in the graphs Biodiversity and soil quality very poor data quality; results discussed qualitatively The actual presentation of the results is different regarding the various questions as well as the individual countries and the EU. They are described in detail within the respective chapters. 4.1.3 Sensitivity analyses Three types of sensitivity analyses were carried out: I Data uncertainty analysis II Different system boundaries III Different life cycle comparisons These are discussed in turn in the following sections. I Data uncertainty analysis While in the calculations minimum-maximum evaluations were carried out, the results for these are not included in the graphs. Two types of methods were used for calculating the ranges: first the minimum and maximum values were calculated using the MonteCarlo method based on standard deviation values. However, it was found that the extreme values using this method are so large/small that a clear presentation including the mean values was not possible. The second method employed was simply to use the minimum and maximum values from the individual countries involved and to calculate average minimum and maximum values from these. As shown in Figure 4-1, this method leads to a clear presentation and also indicates the reliability of the country specific data, as it implies that the results of the various countries are reasonably similar at least regarding the order of magnitude – as should be expected. However, the validity of this method in terms of indicating the range of input data may be questioned. Therefore it was decided to leave the minimum-maximum evaluations out of the general results. II Different system boundaries Concerning different system boundaries, within LCA also described as “different allocation procedures”, two types of sensitivity analyses were carried out. Influence of various credits: during the production of three of the biofuels investigated here, namely RME, SME, and ETBE certain co-products are also produced. Therefore the environmental effects of their equivalent conventional products are considered as credits for the respective biofuel life cycles. In order to show the potential influence of these credits on the final result, in Figure 4-2 the results of the complete life cycle of RME are given as examples – in one case including the credits and in the other

4.1 Introduction 49 case excluding them. Credits are given for the agricultural reference system (for details see the next paragraph), rape seed meal, and glycerine. The result of this comparison indicates that significant differences may result. This shows firstly that it is necessary to include the co-products adequately in the life cycle analyses (in accordance with the principle “from cradle to grave”) as it is done here. Secondly, the results presented here may only be interpreted in the light of the system boundaries (and credits considered) used within this study. Influence of agricultural reference systems: in the calculations of the life cycles of the bioenergy carriers, so-called agricultural reference systems are included (in the form of credits) as described in Chapter 3.2.1. These define the type of land use that would be applied if no bioenergy carriers were to be produced. Figure 4-3 shows the influence of the agricultural reference system on the final result of various life cycle comparisons between biofuels and their corresponding fossil fuels. In each case the result is given with and without the agricultural reference system. Concerning the biofuels shown in the graph, it must be noted that the ratio for the ETBE values is similar to that of the others, but the absolute numbers differ by an order of magnitude, whereas the residues straw and wood show no difference at all as there is no direct change of the agricultural land use. Use of fossil fuels Greenhouse effect Acidification Eutrophication Summer smog Nitrous oxide Human toxicity -15000 -10000 -5000 0 5000 10000 15000 European inhabitant equivalents* per 100 million kWh Figure 4-1 Exemplary data uncertainty analysis for triticale (based on unweighted averages) Concerning the different environmental parameters under concern, the greatest differences of the results are associated with the parameter use of fossil fuels (besides eutrophication as this depends strongly on country specific differences in agricultural practices and conditions). The other parameters show smaller or even much smaller differences. Therefore, use of fossil fuels was chosen for the graph to show the largest occurring differences. The graph indicates that in the cases considered here the agricultural reference system influences the results concerning the production and use of biofuels to a certain degree. But it does not significantly influence the overall results when the biofuel is compared with its fossil counterpart. That means that the chosen reference system does not significantly affect the results. However, it should be noted that the consideration of other agricultural reference systems might lead to completely different results, due to various factors such as transport processes or the cultivation of virgin land (Jungk & Reinhardt 2000).

Bioenergy Update 10-02 - General*Bioenergy
Maximising the environmental benefits of Europe's bioenergy potential
Desktop Management Tools — Which One Is the Best?
Choose The One That Best Fits Your Lifestyle! - Java Fundraiser