Ökobilanz von Danone Activia-Verpackungen aus ... - Foodwatch

150 Ökobilanz von Danone Activia-Verpackungen 2011 IFEU Heidelberg
Data from the analysis of corn yield and land use reveals the relative significance of
this carbon fixation in the soil through conservation tillage practices. The average
corn yield in the twenty-six counties serving the corn wet mill was 0.86 kg/m 2 . The
carbon dioxide fixed by the corn grain is 1,420 g/kg corn or 1,420 x 0.86 = 1,221
g/m 2 . This means that the carbon dioxide „fixed‟ by carbon sequestration in the soil is
about 5% (59/1,221 x 100) of the carbon dioxide fixed by the corn grain itself.
Kim (Kim 2004a) calculated soil organic carbon sequestration for continuously grown
corn under no-tillage conditions for a period of 40 years in 14 counties situated in
seven major corn production states. Results from the DAYCENT model showed that
carbon sequestration rate range from 138 to 250 g CO2/m 2 /year. Sheehan (Sheehan
2003) calculated with the CENTURY model carbon sequestration over a period of 95
years in a continuous corn, no till, no residue collection production system. Results
showed a carbon sequestration rates of about 131 g CO2/m 2 /year. Both values (Kim
and Sheehan) are higher than the no-till scenario (Case II) of Table 1. However, this
value is determined for a corn-wheat-soybean rotation system.
According to Dobermann (Dobermann 2004) one should be cautious about the
potential for soil C sequestration in agricultural no-till systems. Most estimates come
from long term experiments in which some form of conservation tillage is compared
with no-till. In other words, they assume that carbon accumulates once land is
changed to no-till. In most cases, the published carbon sequestration rates range
from about 20 to 60 CO2-C/m 2 /y (or 73-220 g CO2/m 2 /y). He had not seen much
convincing evidence that such rates have been achieved in absolute terms over
larger land areas, under normal production conditions. The preliminary results of new
studies on this, started in 2001, suggest that little C sequestration may occur in
irrigated no-till systems, mainly because residue on the surface is decomposed
quickly rather than transformed into stable soil humus. Not much evidence was seen
for significant carbon accumulation under no-till over a period of 3 years after the
fields had been disked. He recommended to be cautious about the potential for soil C
sequestration in agricultural no-till systems. The greatest uncertainty remains for
irrigated systems, i.e. most of the literature data published come from dryland/rainfed
experiments or, in other papers, are simply simulated changes in soil C with no field
verification.
West (West 2002) reports that preliminary analysis suggests that, on average,
conversion from conventional tillage to no-tillage in the US will result in a
sequestration of 337 � 108 kg C/ha/yr (124 ± 11 g CO2/m 2 /yr) in agricultural soils, to
a depth of 30 cm. This data is based on 76 long-term soil carbon experiments
assembled by the Center for Research on Enhancing Carbon Sequestration in
Terrestrial Ecosystems, US Department of Energy.
Six et al. (Six 2004) compiled all available data of soil-derived GHG emission
comparisons between conventional tilled and no-tillage systems for humid and dry
Endbericht – Bearbeitungsstand 29. März 2011