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BIO-ENERGY CHAINS Sintesi della relazione

Project ID: ENK6-CT-2001-00524
Finanziato nell'ambito di: FP5-EESD
Paese: Germany

Environmental assessment of selected bioenergy chains - LCA

An LCA study was performed to compare the environmental impacts of the different bioenergy chains of perennial crops with respect to their fossil alternatives and among each other, considering their life cycles from the growing region and agriculture to conversion and usage.

Biofuels can help saving energy and greenhouse gases. To some extent they are, however, associated to environmental disadvantages. An objective decision for or against a particular fuel cannot be made. However, based on a subjective value system a decision is possible.

Depending on the crop, the conversion technology, and usage, the environmental effects show at times large or even very large differences. The largest environmental advantages with the smallest environmental disadvantages at the same time can be achieved as follows:
- For obtaining a high environmental benefit, one should grow crops permitting high yields while being ecologically sound.

- In order to produce heat, one should combust biomass directly instead of using the products of gasification or pyrolysis. Only for very advanced technology conversion efficiency can get significantly higher and there is still waste heat left over for heating uses. If one desires to produce electric power or combined heat/power from biomass, the decision whether direct combustion, gasification, or pyrolysis is the best option depends on the individual case.

- For utilising the bioenergy crop the optimal way, every effort should be taken to optimise the efficiency of gasification and pyrolysis and to utilise the waste heat of the conversion processes and pyrolysis residues.

- Given a certain conversion technology, the optimal usage (heat, power, or combined heat/power) depends to a large extent on the individual case.

- If biomass is to be gasified it should be used for heat production at the site of the plant; if it is pyrolysed it should be used rather for power production. If the biomass is to be combusted directly it depends on the single case if heat production or combined heat/power production are preferable.

- For the sake of the greenhouse effect especially light oil should be replaced, only in the second run natural gas.

- If one attaches highest environmental value to the saving of depletable energy resources one should, in the best case, produce electric power from biomass in France in order to replace the French power mix. If, instead, one deems the greenhouse gases most important one should replace the Greek power mix.

The general outcome, e.g. the advantages for biofuels regarding energy savings and greenhouse gases, can generally speaking also be transferred to other bioenergy chains. An exact quantification of the respective life-cycle assessment and
a site-specific environmental impact assessment, however, have to be undertaken for each individual case.

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