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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

144 7 Annex Biogas

144 7 Annex Biogas versus natural gas for combined heat and power production – Italy Use of fossil fuels Greenhouse effect Acidification Eutrophication Summer smog Nitrous oxide** Human toxicity** * How to interpret the diagram Advantages for biofuel Advantages for fossil fuel -7500 -6000 -4500 -3000 -1500 0 1500 3000 4500 Italian inhabitant equivalents* per 100 TJ The figure shows the results of comparisons between complete life cycles where natural gas is substituted by biogas from swine manure for heat and electricity generation. The unit refers to an amount one hundred TJ. This is equivalent to the average heat requirement of about 4,000 inhabitants of Europe in one year. In this case for example the amount of fossil fuel saved is equal to the amount which about 1,100 Italian citizens would on average consume in one year (this is what is meant by “Italian inhabitant equivalents”). Again the use of biogas leads to a reduction of summer smog equal to that that 4700 Italian citizens would cause in one year. Conclusion The results show that both biogas as well as natural gas have certain ecological advantages and disadvantages: • Advantages of the biofuel: use of fossil fuels, greenhouse effect and summer smog • Advantages of fossil fuel: acidification and eutrophication The data for ozone depletion and human toxicity tend to have a high uncertainty. Therefore these categories should not be included in the final assessment. (**For more information on this and the other environmental parameters investigated see Chapters 3.3 and 3.4 as well as 4.1.2.) A further assessment in favour of or against biogas or natural gas cannot be carried out on a scientific basis, because for this purpose subjective value judgements regarding the individual environmental categories are required which differ from person to person. Whether biogas is assessed as better or worse than natural gas depends upon the focus and priorities of the decision makers.

7.1 Country specific life cycle comparisons 145 Ecological aspects: impacts related to saved energy – Italy Greenhouse effect Acidification Eutrophication Summer smog Nitrous oxide** Human toxicity** * How to interpret the diagram Advantages for fossil fuel Advantages for biofuel SME Wood Biogas -3500 -2000 -500 1000 2500 4000 5500 Italian inhabitant equivalents* per 100 TJ of energy saved The figure shows the results of comparisons between complete life cycles where each biofuel under study (SME, Traditional Firewood, Biogas) is substituted to a conventional energy carrier (respectively light oil, diesel, natural gas) for energy production. The results for the various categories are given with reference to the category use of fossil fuels, i.e. 100 TJ of fossil energy saved. For example for every 100 TJ of fossil energy saved through the substitution of diesel fuel by SME the amount greenhouse gas emissions avoided is equal to those on average generated by about 550 Inhabitants of Italy in one year (this is what is meant by “Italian inhabitant equivalents”). On the other hand, in this case for every 100 TJ of energy saved an amount of N2O is emitted that is equal to that on average generated by 3400 Italian inhabitants in one year. Note that in this diagram the advantages of the fossil fuels are on the left hand side and vice versa. Conclusion Comparing the investigated bioenergy carriers (in turn compared to their fossil counterparts) against each other, the following result emerges: Greenhouse effect: for all biofuels a clear advantage over the fossil counterparts can be pointed out. The effect is the greatest for Biogas and lowest for SME. Acidification: Wood has a very low positive impact, whereas SME and Biogas have a negative impact. Eutrophication: SME has a good advantage, whereas Wood and Biogas show disadvantages. Summer smog: all the biofuels show advantages, but the results of SME and Wood are non significant. The data for nitrous oxide and human toxicity tend to have a high uncertainty. Therefore these categories should not be included in the final assessment. (**For more information on this and the other environmental parameters investigated see Chapters 3.3 and 3.4 as well as 4.1.2.). A further assessment in favour of a specific biofuel cannot be carried out on a scientific basis, because for this purpose subjective value judgements regarding the individual environmental categories are required which differ from person to person.

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