I need to analyse C content of biochar sample using Walkley and Black. Can any one give me modified procedure.
The method is primarily used for analysis of soil and in determination of organic carbon in soil. The detailed procedure can be found here.
http://aesl.ces.uga.edu/protected/methods/details/stl-soil/12.html
Walkley and Black method of carbon estimation is applied for soil and it only gives the oxidizable carbon fraction. Walkley and Black method is very much easily available in any of the soil analysis books. However for the carbon estimation in biochar if you applied the same method you will get only the fractions of carbon . So determination of carbon content in biochar need to estimate the total carbon content . hence please try the procedure of total carbon estimation either chemically or with the TOC analyser.
Dear Anjana,
As @ Bibhash above has answered, most appropriate method to analyze C content in biochar may be total combustion of the sample and analyzing the CO2 evolved (referred as: Duma’s combustion). This can be done using the LECO total C analyzer. I have not analyzed biochar myself, but one of my colleagues in our School done this using LECO total C analyzer. He also mentioned the following two papers (listed below). In the paper by Ronsse et al., authors have used an indirect method to characterize biochar including its C fraction (this paper is available at first author’s RG profile). Other paper has used Dumas combustion to directly analyse C content in biochar. If you are not able to get the second paper I can forward a pdf copy.
Ronsse, Frederik. et al. (2013) Production and characterization of slow pyrolysis, biochar: influence of feedstock type and pyrolysis conditions. Global Change Biology –Bioenergy: 5, 104–115, doi: 10.1111/gcbb.12018
Enders, Akio et al. (2012) Characterization of biochars to evaluate recalcitrance and agronomic performance. Bioresource Technology 114: 644–653.
-SJ
Follow this link for Walkley and Black procedure, hope it helps you a lot during your experiment.
https://www.researchgate.net/post/What_is_the_correct_procedure_of_Walkley-Black_method_of_organic_carbon_analysis_in_soil
Regards
As many colleagues have mentioned above, Walkley & Black method is appropriate for the estimation of soil organic matter up to 8%, above this threshold, it becomes inaccurate. For the anlysis of carbon in biochar samples, pyrolysis (loss of ignition) is used for the routine estimation of organic matter by the loss of weight in a sample heated at a temperature high enough to burn organic matter but not so high as to decompose carbonates (Schulte, E.E., and Hopkins, B.G. 1996).
You can also analyze the biochar sample by Dumas method, it's easy with a C-H-N Analyzer.
Good luck
Khalid
ASTM, 2013. D1762-84 Standard Test Method for Chemical Analysis of Wood Charcoal. ASTM International, Conshohocken, PA.
I have 2007 version of this method. this the best method.
I think no organic C retains in the biochar if it was pyrolysed at a temperature >550 Celcius degree for several hours. All C retains in biochar should be inorganic form.
Abbasali Malek Khalid Azim Sandeep Kumar Susantha Jayasundara Tho Nguyen Bibhash Chandra Verma Deepak Kumar Ojha Thank you very much for your suggestions
Typically, biochar organic carbon content increases with increasing pyrolysis temperature. But, I found the carbon content decreases with increasing temperature. However, I found that DOC (Dissolved organic carbon) of biochar decreases with increasing temperature. What could be the explanation?
Note: I used pineapple crown biochar to prepare biochar and I used the Black and Walkley method to determine the carbon content that is used to assess soil organic carbon as I do not have a CHN analyzer facility. I also found only 12-15% of TOC when using the method.
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