Advantages of using chemical fractionation to alkaline extraction for accessing the organic matter in biochar.

abstract

English

This contribution is focused on utilization of a sequential chemical fractionation method for determination of organic matter content, its distribution in biochar and the possible use of biochar as a soil conditioner in agriculture. For these purposes the optimized chemical fractionation procedure [1,2] was used to reveal the content of organic matter in different biochar samples with different properties (samples with European biochar certification for usage in agriculture) which depend significantly on the temperature used during a pyrolysis of biomass residues in the process of biochar production. For the purpose of this study, a biochar from the Czech company BIOUHEL.cz was used. In parallel, these samples were also fractionated by classic alkaline extraction to obtain the so-called extractable fraction of organic matter (NOM – natural organic matter). Biochar is one of the important soil conditioners, known for having positive effect on crop yield, soil quality, nutrient cycle and carbon sequestration due to the transfer of organic carbon from it to the soil. However, the effect depends on the properties of the biochar, its doses to the soil, but also on the properties of the soil itself. Using the sequential chemical fractionation allowed us to separate all the different-strongly bound fractions of similar types of molecules. The alkaline extraction only allowed us to see a mixture of organic molecules contained but overall, this method wasn`t really good to use in order to separate the organic matter from biochar. Individual fractions obtained from sequential chemical fractionation as well as NOM samples were characterized by methods of elemental analysis (determination of organic elements content), thermogravimetry (contents of ash, organic matter and moisture). The results showed that the method of sequential chemical fractionation gives higher yields of organic matter compared to classical alkaline extraction. Overall, the analyzes show that the investigated biochar is a really rigid and durable material that, even after using of aggressive reagents and high temperatures, still contains a high amount of organic matter. The structure couldn`t be cleaved at a level where really strongly bound organic matter could be extracted, which is indicating the high resistance of organic matter in biochar structure. To be able to make more detailed description we will perform chromatographic analysis (GC-MS and LC-MS) which will provide us information on the molecular level of fractions or structural analysis methods (e.g. FTIR, NMR). Another follow-up research will include using these separation methods to characterize a biochar that has been cultivated and treated with soil microorganisms. That will make it possible to better assess their potential effect on biochar in the soil.

fractionation; extraction; biochar; organic matter

ŠIRŮČEK, D.; KALINA, M.; KLUČÁKOVÁ, M.

11. 7. 2022

UA Editora Universidade de Aveiro

Aveiro

978-972-789-771-1

5th International Conference on Nanomaterials Science and Mechanical Engineering

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http://icnmsme2022.web.ua.pt/wp-content/uploads/2022/07/ICNMSME2022-abstracts-book-1.pdf