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| Titel |
The impacts of pyrolysis temperature and feedstock type on biochar properties and the effects of biochar application on the properties of a sandy loam |
| VerfasserIn |
Steve Aston, Stefan Doerr, Alayne Street-Perrott |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082088
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| Zusammenfassung |
| The production of biochar and its application to soil has the potential to make a
significant contribution to climate change mitigation whilst simultaneously improving
soil fertility, crop yield and soil water-holding capacity. Biochar is produced from
various biomass feedstock materials at varying pyrolysis temperatures, but relatively
little is known about how these parameters affect the properties of the resultant
biochars and their impact on the properties of the soils to which they are subsequently
applied.
Salix viminalis, M. giganteus and Picea sitchensis feedstocks were chipped then sieved to
2 – 5 mm, oven dried to constant weight, then pyrolyzed at 350, 500, 600 and 800Ë C in a
nitrogen-purged tube furnace. Biochar yields were measured by weighing the mass of each
sample before and after pyrolysis. Biochar hydrophobicity was assessed by using a
goniometer to measure water-droplet contact-angles. Cation-exchange-capacity
(CEC) was measured using the ammonium acetate method. Biochars were also
produced in a rotary kiln from softwood pellets at 400, 500, 600 and 700Ë C then
ground to 0.4 – 1 mm and applied to a sandy loam at a rate of 50 g kg-1. Bulk
densities of these soil-biochar mixtures were measured on a tapped, dry, basis.
The water-holding-capacity (WHC) of each mixture was measured gravimetrically
following saturation and free-draining. The filter paper method was used to assess
how pyrolysis temperature influences the effect of biochar application on matric
suction.
For all feedstocks, large decreases in biochar yield were observed between the pyrolysis
temperatures of 350Ë C and 500Ë C. For Salix viminalis and M. giganteus feedstocks,
subsequent reductions in the yield with increasing pyrolysis temperature were much lower.
There were significant differences in hydrophobicity between biochars produced
from different biomass and mean biochar hydrophobicity decreased with increasing
pyrolysis temperature for all feedstocks. Results for CEC and WHC measurements will
also be presented. With water contents of 0.04, 0.08 and 0.16 cm3 cm-3, the mean
matric suctions of a sandy loam were higher when biochar was added. However,
the differences were only statistically significant at a water content of 0.16 cm3
cm-3, where biochar produced at 500Ë C had the highest suction. Biochar additions
always lowered the mean bulk density of a sandy loam, but there were significant
differences in the extent to which biochars produced at different temperatures did
this.
Biochar yields and hydrophobicity vary according to feedstock type and decrease with
increasing pyrolysis temperature. Application of biochar can significantly reduce bulk density
but the extent of this effect varies according to the pyrolysis temperature at which the biochar
is produced. Pyrolysis temperature can have a significant influence on how biochars affect
soil suction.
Acknowledgements: This study was funded by a UK Natural Environment Research
Council (NERC) Doctoral Training Grant: NE/H525154/1. |
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