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 N2 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°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.
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References
37
[1]
Bisutti "Determination of total organic carbon—an overview of current methods." TrAC – Trends in Analytical Chemistry (2004) 10.1016/j.trac.2004.09.003
[2]
Brewer "Criteria to select biochars for field studies based on biochar chemical properties." BioEnergy Research (2011) 10.1007/s12155-011-9133-7
[3]
Bundy "A simple titrimetric method for determination of inorganic carbon in soils." Soil Science Society of America Journal (1972) 10.2136/sssaj1972.03615995003600020021x
[4]
Bush "A rapid method for the determination of carbonate carbon and organic carbon." Chemical Geology (1970) 10.1016/0009-2541(70)90006-9
[5]
Calvelo Pereira "Contribution to characterisation of biochar to estimate the labile fraction of carbon." Organic Geochemistry (2011) 10.1016/j.orggeochem.2011.09.002
[6]
Chen "Biomass-based pyrolytic polygeneration system on cotton stalk pyrolysis: Influence of temperature." Bioresource Technology (2012) 10.1016/j.biortech.2011.10.074
[7]
Dean "Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition; comparison with other methods." Journal of Sedimentary Research (1974)
[8]
Donahue "Proximate analysis of coal." Journal of Chemical Education (2009) 10.1021/ed086p222
[9]
Enders "Characterization of biochars to evaluate recalcitrance and agronomic performance." Bioresource Technology (2012) 10.1016/j.biortech.2012.03.022
[10]
Fernandes "How does acid treatment to remove carbonates affect the isotopic and elemental composition of soils and sediments?" Environmental Chemistry (2008) 10.1071/en07070
[11]
Gunasekaran "Thermal decomposition of natural dolomite." Bulletin of Materials Science (2007) 10.1007/s12034-007-0056-z
[12]
Harris "Acid fumigation of soils to remove carbonates prior to total organic carbon or carbon-13 isotopic analysis." Soil Science Society of America Journal (2001) 10.2136/sssaj2001.1853
[13]
Harvey "An index-based approach to assessing recalcitrance and soil carbon sequestration potential of engineered black carbons (biochars)." Environmental Science & Technology (2012) 10.1021/es2040398
[14]
Heiri "Loss on ignition as a method for estimating organic and carbonate content in sediments: Reproducibility and comparability of results." Journal of Paleolimnology (2001) 10.1023/a:1008119611481
[15]
International Biochar Initiative (2012) Guidelines for specifications of biochars for use in soils. International Biochar Initiative. Available at: www.biochar-international.org/
[16]
Keiluweit "Dynamic molecular structure of plant biomass-derived black carbon (biochar)." Environmental Science & Technology (2010) 10.1021/es9031419
[17]
Keith "Interactive priming of biochar and labile organic matter mineralization in a smectite-rich soil." Environmental Science & Technology (2011) 10.1021/es202186j
[18]
Lehmann "Bio-char sequestration in terrestrial ecosystems—a review." Mitigation and Adaptation Strategies for Global Change (2006) 10.1007/s11027-005-9006-5
[19]
Lin "Migration of dissolved organic carbon in biochars and biochar-mineral complexes." Pesquisa Agropecuaria Brasileira (2012) 10.1590/s0100-204x2012000500007
[20]
Macías "Soil carbon sequestration in a changing global environment." Mitigation and Adaptation Strategies for Global Change (2010) 10.1007/s11027-010-9231-4
[21]
[22]
[23]
[24]
[25]
Schimmelpfennig "One step forward toward characterization: Some important material properties to distinguish biochars." Journal of Environmental Quality (2012) 10.2134/jeq2011.0146
[26]
Singh "Long-term influence of biochar on native organic carbon mineralisation in a low-carbon clayey soil." Scientific Reports (2014) 10.1038/srep03687
[27]
[28]
Singh "Characterisation and evaluation of biochars for their application as a soil amendment." Soil Research (2010) 10.1071/sr10058
[29]
Singh "Biochar carbon stability in a clayey soil as a function of feedstock and pyrolysis temperature." Environmental Science & Technology (2012) 10.1021/es302545b
[30]
Walthert "Determination of organic and inorganic carbon, d13c, and nitrogen in soils containing carbonates after acid fumigation with HCl." Journal of Plant Nutrition and Soil Science (2010) 10.1002/jpln.200900158
[31]
Wang "Optimizing the weight loss-on-ignition methodology to quantify organic and carbonate carbon of sediments from diverse sources." Environmental Monitoring and Assessment (2011) 10.1007/s10661-010-1454-z
[32]
Wang "Comparisons of three methods for organic and inorganic carbon in calcareous soils of northwestern china." PLoS ONE (2012) 10.1371/journal.pone.0044334
[33]
Wang "Predicting phosphorus bioavailability from high-ash biochars." Plant and Soil (2012) 10.1007/s11104-012-1131-9
[34]
Wang "Chemical and bioassay characterisation of nitrogen availability in biochar produced from dairy manure and biosolids." Organic Geochemistry (2012) 10.1016/j.orggeochem.2012.07.009
[35]
Wu "Removal and recycling of inherent inorganic nutrient species in mallee biomass and derived biochars by water leaching." Industrial & Engineering Chemistry Research (2011) 10.1021/ie200679n
[36]
Yuan "Effects of biochars generated from crop residues on chemical properties of acid soils from tropical and subtropical china." Soil Research (2012) 10.1071/sr12118
[37]
Yuan "The forms of alkalis in the biochar produced from crop residues at different temperatures." Bioresource Technology (2011) 10.1016/j.biortech.2010.11.018
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