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| Titel |
N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels |
| VerfasserIn |
P. J. Crutzen  , A. R. Mosier, K. A. Smith, W. Winiwarter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 2 ; Nr. 8, no. 2 (2008-01-29), S.389-395 |
| Datensatznummer |
250005432
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| Publikation (Nr.) |
 copernicus.org/acp-8-389-2008.pdf |
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| Zusammenfassung |
| The relationship, on a global basis, between the amount of N fixed by
chemical, biological or atmospheric processes entering the terrestrial
biosphere, and the total emission of nitrous oxide (N2O), has been
re-examined, using known global atmospheric removal rates and concentration
growth of N2O as a proxy for overall emissions. For both the
pre-industrial period and in recent times, after taking into account the
large-scale changes in synthetic N fertiliser production, we find an overall
conversion factor of 3–5% from newly fixed N to N2O-N. We assume the
same factor to be valid for biofuel production systems. It is covered only
in part by the default conversion factor for "direct" emissions from
agricultural crop lands (1%) estimated by IPCC (2006), and the default
factors for the "indirect" emissions (following volatilization/deposition
and leaching/runoff of N: 0.35–0.45%) cited therein. However, as we
show in the paper, when additional emissions included in the IPCC
methodology, e.g. those from livestock production, are included, the total
may not be inconsistent with that given by our "top-down" method. When the
extra N2O emission from biofuel production is calculated in
"CO2-equivalent" global warming terms, and compared with the
quasi-cooling effect of "saving" emissions of fossil fuel derived
CO2, the outcome is that the production of commonly used biofuels, such
as biodiesel from rapeseed and bioethanol from corn (maize), depending on N
fertilizer uptake efficiency by the plants, can contribute as much or more
to global warming by N2O emissions than cooling by fossil fuel savings.
Crops with less N demand, such as grasses and woody coppice species, have
more favourable climate impacts. This analysis only considers the conversion
of biomass to biofuel. It does not take into account the use of fossil fuel
on the farms and for fertilizer and pesticide production, but it also
neglects the production of useful co-products. Both factors partially
compensate each other. This needs to be analyzed in a full life cycle
assessment. |
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