화학적 산화를 이용한 농축산 부산물 기반 바이오차 탄소 격리 효과의 정량적인 예측 = Quantitative Estimation on Carbon Sequestration Potential of Agricultural By-products Biochar using Chemical Oxidation

다국어 초록 (Multilingual Abstract)

Biochar is considered a promising carbon sequester for mitigating climate change. However, carbon in the biomass is partially lost during pyrolysis by releasing gases such as CO and CH4. In addition, biochar contains labile carbon to be mineralized by soil microbes, potentially reducing its actual carbon sequestration potential. Therefore, quantifying unstable carbon in biochar is essential to accurately evaluate biochar's carbon sequestration potential. Chemical oxidation has been used as a rapid method to quantify the unstable carbon in biochar. Although lots of studies on the quantification of unstable carbon have used chemical oxidation, it is unclear whether the unstable carbon fraction by chemical oxidation is mineralized in soil or not. Therefore, this study aims to establish a chemical oxidation method by matching the chemically oxidized carbon of biochar with the fraction mineralized in soil and to quantify the carbon sequestration potential of biochar. Firstly, the chemical oxidation method was optimized to oxidize unstable carbon. Among various oxidants, K2Cr2O7/H2SO4 was selected as an optimal oxidant due to its high oxidation potential and minimal influence on the properties of biochar. Thereafter, applying biochar made from agricultural by-products, 30 mmol/g biochar (K2Cr2O7/H2SO4) showed a strong correlation with mineralized carbon (R² = 0.87, p = 0.01), confirming its applicability under optimal conditions.
Based on the proposed chemical oxidation method, hanwoo manure and swine manure-derived biochar showed the highest carbon sequestration potential. The results indicate that the characteristics of feedstock and pyrolysis carbon loss significantly influence the carbon sequestration potential. Therefore, chemical oxidation offers an effective strategy to assess the carbon stability of biochar without long-term incubation.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• 1.1 Climate Change 1
• 1.2 Biochar 2
• 1.3 Qualitative Estimation on Carbon Stability of biochar 4
• 1.4 Quantitative Estimation on Carbon Stability of biochar 6
• 1.5 Research objectives 9
• Chapter 2. Materials and Methods 10
• 2.1 Chemicals and materials 10
• 2.2 Characterization of biochar 11
• 2.3 Incubation experiments 13
• 2.4 Chemical oxidation experiments 15
• Chapter 3. Results and Discussion 17
• 3.1 Characteristics of biochar 17
• 3.1.1 Physicochemical properties of biochar 17
• 3.1.2 Surface functional groups of biochar 21
• 3.1.3 Degree of condensed aromatic carbon structure 23
• 3.1.4 Thermogravimetric analysis 26
• 3.2 Incubation 30
• 3.3 Chemical oxidation 34
• 3.3.1 KMnO4 oxidation according to dose 34
• 3.3.2 H2O2 oxidation according to dose 37
• 3.3.3 K2Cr2O7/H2SO4 oxidation according to dose 40
• 3.3.4 Quantification of labile fraction according to types of feedstock 43
• 3.3.5 Qualitative analysis of biochar after oxidation 46
• 3.3.6 Incubation of oxidized biochar 50
• 3.4 Correlation with incubation and chemical oxidation 53
• 3.5 Carbon sequestration potential of biochar 55
• Chapter 4. Conclusions 58
• References 60