Methodology of Carbon Sink Accounting and Evaluation Model for the Full Chain of "Consolidation-Carbon Sequestration-Transaction" of Arable Land

The urgent challenge of climate change has made carbon neutrality a central policy goal worldwide.Farmland soil in China holds significant potential for carbon sequestration, yet small-scale, scattered household management has constrained the development of large-scale farmland carbon sink projects. To address this gap, this study constructs a full-chain methodological framework of “Consolidation-Carbon Sequestration-Transaction,” integrating land consolidation theory, agroecological principles, and ecosystem service valuation. A “scale-cost-benefit” analysis model was developed to quantify the economic viability of farmland carbon sinks under different land-use conversion scenarios. Results show that under the current carbon price of 40 yuan/ton, the per-mu benefit of farmland carbon sequestration is only 8–12 yuan, which is insufficient to cover monitoring and transaction costs at small scales. However, when farmland is consolidated into contiguous plots, costs can be reduced by 30–40%, allowing the cost-benefit balance point to be reached. This study provides a standardized quantitative method for farmland carbon sink evaluation, offering practical guidance for designing large-scale carbon sequestration projects in China. Furthermore, the proposed framework has broader international relevance for countries with smallholder-dominated agricultural structures, where land consolidation and carbon sink standardization can similarly promote sustainable agricultural modernization and climate mitigation.