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BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

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156 7 Annex<br />

Eutrophication potential for wood is larger because of the higher NH3 emissions at combustion. Slurry<br />

from the biogas plant contains a bit more nitrogen in the mineral form, which increases the risk of NH3<br />

emissions and NO3 - leaching and consequently causes a worse result for the biogas system.<br />

Summer smog (photochemical ozone creation potential POCP) – Switzerland<br />

POCP not only depends on hydrocarbons, included as NMVOC emissions, but also on methane. This is<br />

important for the biogas system in which no methane is emitted during slurry storage, resulting in a<br />

lower score than that of its reference system (see result table below). For the two other investigated<br />

biofuels systems, the differences of the NMVOC emissions explain the results.<br />

Impact category RME Diesel Wood Light oil Natural<br />

gas<br />

Summer smog<br />

g ethen eq./MJ<br />

Eutrophication g<br />

NO3 - eq. /MJ<br />

Ozone depletion by<br />

nitrous oxide in<br />

g N2O /MJ<br />

MJ refers to MJ of useful energy<br />

Ozone depletion by nitrous oxide – Switzerland<br />

Biogas Natural<br />

gas<br />

0.11 0.12 0.02 0.01 0.02 0.05 0.1<br />

4.1 7.6 0.2 0.1 0.1 0.5 0.1<br />

0.437 0.020 0.001 0.001 0.001 0.003 0.001<br />

For this impact category only the N2O emissions are included. RME has a considerably higher potential<br />

than its fossil alternative because of the possible denitrification of the fertiliser used (see result table<br />

above).<br />

Human toxicity – Switzerland<br />

The impact on human toxicity depends mainly on heavy metals, pesticides, NOx, SO2 and particles.<br />

Biogas has a higher score than CHP from natural gas because of higher SO2 emissions. In spite the fact<br />

that wood burning causes more particles, the toxicity potential for heating oil is higher due to more<br />

heavy metals emitted in different processes (see result diagram below).<br />

40000<br />

35000<br />

30000<br />

25000<br />

20000<br />

15000<br />

10000<br />

5000<br />

0<br />

Summary and conclusion<br />

Humantoxicity (m3/MJ useful energy)<br />

Processing & utilisation<br />

Agriculture/forestry part<br />

Fossil fuel life cycle<br />

Agricultural reference system<br />

RME Diesel Wood Heating oil Natural Gas Biogas Natural Gas<br />

In the result table below there is an overview of the advantages and disadvantages from the biofuels<br />

compared to their fossil counterparts. The scheme for determining and assessing the significance of the<br />

results for each impact category was published in Wolfensberger and Dinkel (1997).

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