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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

40 3 Life cycle

40 3 Life cycle assessment of biofuels: methods and tools Ecosystem occupation as a measure for life support functions of the soil: soil quality is an important element of life support functions. A soil with a good quality is able on the one hand to maintain a diversified and active biological activity and a typical soil structure for the site, and on the other hand to guarantee sufficient, good and safe products for man and animals in high crop yields for its type and climate. Cowell (1998) defines changes of organic matter as one factor concerning soil suitable for inclusion in an LCA. An indicator close to organic matter added to the soil is the free net primary biomass productivity. This is simply the total biomass dry matter grown on one hectare in a year, minus the biomass removed from the field in harvest. Lindeijer et al. (1998) have proposed to use free net primary biomass productivity as an indicator for the potential of nature development, as it expresses the amount of biomass free for development of higher species. The complete formula for ecosystem occupation as a measure for life support is listed in the external annex (see Annex 7.5). This method “ecosystem occupation as a measure for life support functionality” is used in this study. Tentative calculations have been carried out with this method. Since the results obtained for this parameter show significant qualitative differences compared to those for the impact categories described in Chapter 3.4.2, they are presented separately in Chapter 4.2.10. Harmful rainfall as an indicator of erosion: especially in areas with mountains the risk of erosion is high. The quantity of eroded soil can be measured, but should in most cases (due to lack of data) be calculated with the (revised) Universal Soil Loss Equation. (For details on this equation see Annex 7.5). Most factors in the formula are fixed for a certain location, at least on a short-term basis. Two factors are different between crops: the rainfall factor R and the crop management factor C. In this project, values for C and R per crop stage were collected and multiplied (R*C) which gives the amount of harmful rainfall. Finally the harmful rainfall data per crop stage are summed up to give one result per energy crop. This indicator is also suggested by Cowell (1998). It should be noted however, that according to Wolfensberger & Dinkel (1997) the factor C is the central one, which may lead to different results than those obtained in this study. Since the results obtained for this parameter show significant qualitative differences compared to those for the impact categories described in Chapter 3.4.2, they are presented separately in Chapter 4.2.10. Soil compaction: again, Cowell (1998) suggests this parameter as a factor to be considered in an environmental assessment. Soil compaction by the use of machines is an important problem in agriculture. Compaction is related to the weight of tractors and machinery, tyre width and tyre pressure, as well as soil humidity. Available formulae are incomplete, e.g. they do not include the clay and water content. The best would be to use the most complete method (Wolfensberger & Dinkel 1997). Due to the large additional data acquisition required, it was not possible to collect data for all countries. Therefore finally no scores were calculated for soil compaction in this study. 3.4.2 Description of the impact categories There is a fairly stable consensus upon how to treat some of these environmental impacts in life cycle assessments. This is especially the case for global warming or acidification. For others, such as the toxicological impacts, there exists a diversity of methods. Only methodologies specially used in this project are reported hereafter. The coefficients used are given in Chapter 3.4.3. Use of fossil fuels Contrary to the more general category of abiotic resources, the methodologies are in relative agreement for the energy resources. In this project, the finite energy carriers are characterised through their lower calorific value, because it represents the amount of energy that is practically derived from the fuel in most plants. Greenhouse effect The Intergovernmental Panel on Climate Change (IPCC) has developed an equivalence factor system, which expresses the various climate-forcing substances in the same reference unit, i. e. CO2-equivalents (Houghton et al., 1995). This procedure is based on expert judgements of scientists world wide and has gained international acceptance.

3.4 Impact assessment 41 The IPCC provides values for three different time horizons: 20, 100 and 500 years. For this project, the 100- and the 500-year time horizons were chosen. The characterisation factors used for calculating these are given in Table 3.2 in Chapter 3.4.3. In the results, only the values for the 500-year time horizon are given. Acidification Heijungs et al. (1992) suggest an equivalence factor system, which expresses the various substances in one reference unit, i. e. SO2-equivalents, according to their efficiency in reducing the ecosystem’s acid neutralising capacity. This is called the Acidifying Potential (AP). This procedure is based upon simple assumptions about the chemical formations that the substances usually form. The characterisation factors used for calculating the results are given in Table 3.2 in Chapter 3.4.3. Eutrophication Heijungs (1992) and Hauschild and Wenzel (1998) suggest an equivalence factor system, where the nitrogen- and phosphorus-related problems can be assessed individually and aggregated by either assessing the total emission of N, P, or using a reference unit NO3-equivalents in proportion to the average N/P-relationship in biomass. The characterisation factors used for calculating the results are given in Table 3.2 in Chapter 3.4.3. Summer smog The potential contribution to photochemical ozone creation from a substance is described by its Photochemical Ozone Creation Potential (POCP). This is calculated on the basis of knowledge about the types of reactions that the substance undergoes with other substances present in the troposphere, and the rate at which the various reactions proceed. The POCP-values vary between regions with high or low concentrations of NOx (see Hauschild and Wenzel, 1998). Low NOx is most relevant for Scandinavia, whereas high NOx values are more relevant in the rest of Europe. Therefore, characterisation factors for high NOx conditions are used as worstcase default. Ozone depletion by nitrous oxide The first concept for this impact category was introduced by Wuebbles (1988) and further developed by the World Meteorological Organisation (WMO), which has compiled an equivalence factor system that expresses the various substances in the reference unit “CFC11-equivalents” (WMO 1995). This is called the Ozone Depletion Potential (ODP). The procedure for its calculation is based on expert judgements of scientists world wide and has gained international acceptance. But, since in the processes studied in the present project, N2O is the only one substance contributing to a change of the stratospheric ozone layer, the assessment regarding ozone depletion has been performed on the basis of the inventory analysis, i. e. the parameter N2O only. It must be noted that it is scientifically proven that N2O has a twofold influence on the ozone layer (ozone depletion through direct and indirect processes; ozone formation through a direct process), but it is not yet established whether this leads to a net increase or decrease (Reinhardt and Zemanek 2000). Taking this fact into account, only the balance of the parameter N2O is given in this study, without linking it directly with ozone depletion. Human toxicity Toxic substances emitted to the environment also contribute to human toxicity. The distribution of human toxicity between air, water and soil follow the same principles as discussed briefly for ecotoxicity above (Chapter 3.4.1). The impact upon human health depends largely upon where the emission takes place (to air, water or soil), and whether humans are exposed through air, soil, surface water or groundwater.

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