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| Titel |
Biochar degradation in different soils |
| VerfasserIn |
B. Wilske, M. Bai, C. Eckhardt, C. Kammann, P. Kraft, M. Bach, H.-G. Frede, L. Breuer |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069392
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| Zusammenfassung |
| Current expectations in biochar products (BC) are numerous, e.g., including improved soil
fertility & plant growth, support to combat desertification, and an increase in the carbon
sequestration of soils. Costs for biochar production & application must be covered by a
positive budget of benefits, which may crucially depend on the residence time (or half life
T1-2, yr) of BC in soils. The objective of the present study was to assess the biodegradation
rates of BC in different soils by means of a cost-efficient and standardized laboratory
method.
Investigated BC were from the source material of the C4 plant Miscanthus, and
converted via (1) pyrolysis (pyrBC) and (2) hydrothermal carbonization (htcBC). The
high-labelling of the educt allowed the quantification of degradation by measurement of the
13CO2 efflux. The pyrBC and htcBC were mixed with four different agricultural soils
ranging in texture from sand to loam and in soil organic carbon (SOC) from 0.63% to
2.53%.
Four samples of each BC-soil combination (1% BC wt/wt in a 300-g sample mixture) and
soil-only reference were incubated in 1-L glass bottles at 40% water holding capacity and
25Ë C. Biodegradation of BC was monitored weekly over a period of 7 months
using an automated open-dynamic chamber system. The system couples the batch
of samples to microprocessor- controlled valves, by which flushing is provided
for the batch, while individual samples are consecutively connected through to a
wavelength scan cavity ring down spectrometer (WS-CRDS). Net 13CO2 efflux from BC
was obtained by subtracting the 13CO2 efflux from “soil-only” samples. T1-2 was
calculated based on the ln(k)-based algorithm recently suggested by Zimmerman et al.
(2010).
Results show an orders-of-magnitude larger T1-2 of BC in poor sandy soil than in
SOC-richer soils (T1-2 up to 106 yrs) but not a statistically clear trend of biodegradability
along the four-point SOC gradient. This was similar in both BC types, although T1-2 was
generally shorter for htcBC than for pyrBC.
Results are consistent with the general understanding of which are the main and the
contributing drivers of BC degradability. The large variability in T1-2 obtained within
the individual BC-soil mixtures seems at least as much a product of the algorithm
sensitivity as of the samples’ preparation, incubation, and measurement together. |
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