BIOENERGY FOR EUROPE: WHICH ONES FIT BEST?

7.1 Country specific life cycle comparisons 113
Wheat straw versus light oil or natural gas for heat production – Denmark
Use of fossil fuels
Greenhouse effect
Acidification
Eutrophication
Summer smog
Nitrous oxide**
Humantoxicity**
* How to interpret the diagram:
Advantages for
biofuel
Advantages for
fossil fuel
Straw vs light oil
Straw vs natural gas
-1000 -500 0 500 1000 1500
Danish inhabitant equivalents* per 100 TJ
The figure shows the results of comparisons between complete life cycles where light oil (blue) or natural
gas (light blue) is substituted by wheat straw for heat production. The unit refers to an amount of
100 TJ of heat. This is equivalent to the average heat requirement of about 4,700 inhabitants of Denmark
in one year or a wheat straw production of about 2,200 ha/a.
Conclusion
The results show that both wheat straw as well as light oil/natural gas have certain ecological advantages
and disadvantages, depending on the parameters given highest priority. Thus for example, wheat
straw has significant environmental advantages over the fossil fuels with regard to the parameters
greenhouse effect and use of fossil fuels but on the other hand light oil and natural gas is superior with
regard to nitrous oxide, summer smog and human toxicity. The other parameters show less significant
result in favour of fossil fuel. As mentioned, the data for human toxicity tend to have a uncertainty
higher than average, and should therefore 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 wheat straw or light oil/natural gas cannot be carried
out on a scientific basis, because for this purpose subjective value judgements regarding the individual
environmental categories are required. Whether wheat straw is assessed as better or worse than light oil
depends upon the focus and priorities of the decision makers. If the main focus of the decision maker is
for example on the reduction of the greenhouse effect and the saving of energy resources, wheat straw
will be better suited. If on the other hand the parameter nitrous oxide is deemed to be most important,
then light oil or natural gas would be preferred.