Determination of carbonate-C in biochars
(2014) In Soil Research 52(5). p.495-504- Abstract
- Although carbonate-carbon (C), an integral part of biochar-C, contributes to the liming properties of that material, it also interferes with the estimation of the stable organic C fraction in biochars. In this study, four methods were compared in order to quantify the carbonate-C in biochars: two direct (a titrimetric procedure and thermogravimetric analysis, TGA), and two indirect (acid treatment with separation by filtration and acid fumigation). The titrimetric method showed a high recovery of added carbonate-C (average 98.8%, range 1.5-38 mg), and the standard deviations of carbonate-C for all biochars tested were <0.1% when 1 g of sample was used. The acid treatment with a filtration step overestimated the carbonate-C content (on... (More)
- Although carbonate-carbon (C), an integral part of biochar-C, contributes to the liming properties of that material, it also interferes with the estimation of the stable organic C fraction in biochars. In this study, four methods were compared in order to quantify the carbonate-C in biochars: two direct (a titrimetric procedure and thermogravimetric analysis, TGA), and two indirect (acid treatment with separation by filtration and acid fumigation). The titrimetric method showed a high recovery of added carbonate-C (average 98.8%, range 1.5-38 mg), and the standard deviations of carbonate-C for all biochars tested were <0.1% when 1 g of sample was used. The acid treatment with a filtration step overestimated the carbonate-C content (on average by a 4-fold increment) due to the loss of dissolved or fine particulate organic C during filtration. The acid fumigation method was suitable for biochars containing high amount of carbonate-C (>0.3% wt) and when the isotopic signature of organic C in biochars is to be determined. The TGA method (either in N-2 or a dry air atmosphere) was reliable when calcite was the main carbonate form in biochars, but was inadequate for samples containing a considerable amount of whewellite and certain carbonate-bearing minerals (e. g. magnesite) that decompose at <600 degrees C. Because more than half of the biochar samples investigated in the literature and in this study (58% of the 117 samples) contained <0.4% carbonate-C (and 38% of these contained no detectable carbonate-C), low-cost screening methods were developed to identify the biochars needed for carbonate-C analysis. For this purpose, two methods were proposed: (i) a manometric test; and (ii) a ratio between predicted fixed C : total C (FC/TC) and measured FC/TC, where predicted FC/TC was estimated using the following relationship: (FC/TC) = -0.1081(H/C)(2) - 0.1794(H/C) + 1.0097, as derived from values obtained in the literature. A decision tree, including two steps (a screening step and a titrimetric procedure) could be used to determine accurately the carbonate-C in biochars. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/8034176
- author
- Wang, Tao LU ; Camps-Arbestain, Marta ; Hedley, Mike ; Singh, Bhupinder Pal ; Calvelo-Pereira, Roberto and Wang, Congying
- organization
- publishing date
- 2014
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Soil Research
- volume
- 52
- issue
- 5
- pages
- 495 - 504
- publisher
- CSIRO Publishing
- external identifiers
-
- scopus:84903396668
- ISSN
- 1838-675X
- DOI
- 10.1071/SR13177
- language
- English
- LU publication?
- yes
- additional info
- 5
- id
- 62d48365-fb92-4624-baeb-a36fb05c433d (old id 8034176)
- date added to LUP
- 2016-04-01 10:57:47
- date last changed
- 2022-04-28 03:14:09
@article{62d48365-fb92-4624-baeb-a36fb05c433d,
abstract = {{Although carbonate-carbon (C), an integral part of biochar-C, contributes to the liming properties of that material, it also interferes with the estimation of the stable organic C fraction in biochars. In this study, four methods were compared in order to quantify the carbonate-C in biochars: two direct (a titrimetric procedure and thermogravimetric analysis, TGA), and two indirect (acid treatment with separation by filtration and acid fumigation). The titrimetric method showed a high recovery of added carbonate-C (average 98.8%, range 1.5-38 mg), and the standard deviations of carbonate-C for all biochars tested were <0.1% when 1 g of sample was used. The acid treatment with a filtration step overestimated the carbonate-C content (on average by a 4-fold increment) due to the loss of dissolved or fine particulate organic C during filtration. The acid fumigation method was suitable for biochars containing high amount of carbonate-C (>0.3% wt) and when the isotopic signature of organic C in biochars is to be determined. The TGA method (either in N-2 or a dry air atmosphere) was reliable when calcite was the main carbonate form in biochars, but was inadequate for samples containing a considerable amount of whewellite and certain carbonate-bearing minerals (e. g. magnesite) that decompose at <600 degrees C. Because more than half of the biochar samples investigated in the literature and in this study (58% of the 117 samples) contained <0.4% carbonate-C (and 38% of these contained no detectable carbonate-C), low-cost screening methods were developed to identify the biochars needed for carbonate-C analysis. For this purpose, two methods were proposed: (i) a manometric test; and (ii) a ratio between predicted fixed C : total C (FC/TC) and measured FC/TC, where predicted FC/TC was estimated using the following relationship: (FC/TC) = -0.1081(H/C)(2) - 0.1794(H/C) + 1.0097, as derived from values obtained in the literature. A decision tree, including two steps (a screening step and a titrimetric procedure) could be used to determine accurately the carbonate-C in biochars.}},
author = {{Wang, Tao and Camps-Arbestain, Marta and Hedley, Mike and Singh, Bhupinder Pal and Calvelo-Pereira, Roberto and Wang, Congying}},
issn = {{1838-675X}},
language = {{eng}},
number = {{5}},
pages = {{495--504}},
publisher = {{CSIRO Publishing}},
series = {{Soil Research}},
title = {{Determination of carbonate-C in biochars}},
url = {{http://dx.doi.org/10.1071/SR13177}},
doi = {{10.1071/SR13177}},
volume = {{52}},
year = {{2014}},
}