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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

136 7 Annex Use of

136 7 Annex Use of fossil fuels – Greece The production and use of all biofuels under study instead of their fossil counterparts result in net savings of fossil fuels. The substitution of diesel oil with SME results in a net finite energy gain of 2.8 MJ/MJ useful energy while the respective value for biogas is 1.4 MJ/MJ useful energy. In the case of wheat straw energy savings are up to 1.2 MJ/MJ useful energy when it replaces light oil and 1.4 MJ/MJ useful energy when it replaces natural gas. The energy requirements per MJ of useful energy are higher in the SME chain compared to the other two biofuels mainly due to increased energy demand during the production of the raw material (sunflower seed). However, SME proves to be the most favourable biofuel in this impact category saving twice as much energy as the other two biofuels. MJ / MJ useful energy 2 1.75 1.5 1.25 1 0.75 0.5 0.25 0 Greenhouse effect – Greece g CO 2 eq. / MJ useful energy 500 400 300 200 100 0 4 Processing & Utilisation Agriculture/forestry part Fossil fuel life cycle Agricultural reference system SME Diesel Biogas Natural gas Straw Light oil Natural gas Processing & Utilisation Agriculture/forestry part Fossil fuel life cycle Agricultural reference system SME Diesel Biogas Natural gas Straw Light oil Natural gas

7.1 Country specific life cycle comparisons 137 All biofuels under study result in savings of greenhouse gas emissions. The substitution of natural gas with biogas saves 404 g CO2 eq./MJ useful energy, diesel oil with SME 144 g CO2 eq./MJ useful energy and light oil with straw 87 CO2 eq./MJ useful energy. Straw instead of natural gas saves 74 CO2 eq./MJ useful energy. The advantage of biogas in this impact category can be attributed to CH4 use as a fuel in the biogas chain instead of its uncontrolled release to the environment in the reference system as well as the avoided CO2 emissions from the substitution of a fossil fuel with a biofuel. Acidification – Greece Acidification is an impact category in which all biofuels under study present worse results than the reference fossil fuel. The least favourable biofuel is biogas emitting 1.7 g SO2 eq./MJ useful energy more than natural gas due to increased SO2 and NOx emissions from biogas combustion. The increased acidifying emissions in the SME chain (0.5 g SO2 eq./MJ useful energy) are in the agricultural part mainly due to NH3 emissions from nitrogen fertilisation while in the case of straw increased emissions are due to straw combustion. g SO2 eq. / MJ useful energy 6 5 4 3 2 1 0 Eutrophication – Greece Processing & Utilisation Agriculture/forestry part Fossil fuel life cycle Agricultural reference system SME Diesel Biogas Natural gas Straw Light oil Natural gas In the impact category eutrophication all biofuels present worse results compared to their fossil counterparts. In the biogas chain NOx emissions from biogas combustion are mainly responsible for the increased emissions of the biogas chain (0.52 g NO3 eq./MJ useful energy more than in the natural gas chain).In the SME chain as shown in the above figure 7.37 g NO3 eq./MJ useful energy are subtracted from the total emissions of the chain due to system expansion (see Chapter 3.2.4., glycerine and sunflower meal) and therefore SME emits 0.67 g NO3 eq./MJ useful energy more than diesel oil through its life cycle due to increased emissions in the agriculture/forestry part. Wheat straw proves to be the least disadvantageous biofuel in this impact category emitting 0.16 NO3 eq./MJ useful energy more than light oil and natural gas.

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