Abstract: Objective Against the backdrop of China's determined pursuit of the "Dual Carbon" strategy, accurate quantification and effective management of carbon dioxide (CO2) emissions have emerged as critical imperatives across all industrial sectors. The municipal solid waste incineration industry is responsible for treating 254 million tons of waste annually, accounting for 82.5% of the country's municipal waste treatment, and is a significant contributor to greenhouse gas emissions. In 2020 alone, waste incineration and landfill processes in China generated 72.1 million tons of greenhouse gas emissions. So as the proportion of waste treated through incineration continues to increase, it has created substantial pressure for emission reduction. The complex nature of emissions from municipal solid waste incineration, which is derived from the combustion of carbon-containing materials in both waste and auxiliary fuels, combined with regional variations in waste composition and incineration technologies, necessitates sophisticated monitoring approaches. Current carbon quantification methodologies predominantly rely on emission factor-based accounting methods, while comprehensive comparative studies incorporating actual measurement approaches remain insufficiently explored. This methodological shortcomning has significantly constrained the development of precise monitoring frameworks essential for carbon market operations and evidence-based policy formulation. This study addresses this critical research need by conducting an extensive empirical investigation on CO2 emissions from two representative waste incineration units, employing a multi-methodological approach that includes both actual measurement techniques (manual sampling and online monitoring) and traditional accounting methods. Through carefully designed controlled experiments that take into account the operational specificities and emission profiles of the incineration units, this study conducts systematic on-site measurements under various load conditions, to thoroughly validate the applicability and feasibility of different emission testing technologies while quantitatively analyzing the discrepancies between methodological approaches. By establishing a robust comparative framework and generating much-needed empirical data, this study aims to provide a scientific basis for enhancing carbon emission accounting accuracy in waste management sectors. The research results are expected to contribute greatly to the development of more reliable monitoring, reporting, and verification systems, thereby supporting China's strategic objectives in carbon peak attainment and carbon neutrality realization, and promoting the advancement of green, low-carbon development strategies nationwide. Methods This study systematically investigated the carbon emissions from two 750 t/d municipal solid waste incineration units operating under three distinct steam load conditions (65%, 75%, and 85% capacity). The experimental design adopted a comprehensive methodological framework integrating three complementary approaches: guideline-based accounting methods following China's official greenhouse gas emission accounting standards, direct measurement techniques utilizing non-dispersive infrared spectroscopy for manual sampling and Fourier transform infrared technology for online continuous monitoring, and rigorous quality assurance protocols. The study established controlled experimental conditions with detailed parameter monitoring, including detailed recording of fuel input rates, ash residue quantities, and simultaneous sampling of input waste and incineration residues for laboratory analysis. A sophisticated quality assurance system was implemented, featured with identical calibration procedures for all monitoring equipment, strategic sampling positioning to ensure uniform flow distribution, and robust verification mechanisms including blind sample comparison and certified reference material verification. This integrated methodology enabled direct comparison between accounting-based and measurement-based approaches under stabilized operational conditions, with particular attention to maintaining consistent pollution control system performance throughout all testing stages. The experimental design specifically addressed methodological comparability by synchronizing measurement timelines, utilizing consistent fuel sources, and implementing parallel sampling procedures with triplicate specimens and standardized sample preparation protocols, thereby establishing a reliable foundation for assessing the applicability and feasibility of different carbon emission quantification techniques in real waste incineration operations. Results and Discussion The comparative analysis of CO2 emissions from two waste incineration units using online monitoring, manual sampling, and accounting methods shows that, although there are observable deviations, generally comparable results for different methods are achieved. The unit load rate has a significant influence on the results. At higher loads (85%), the deviation between measured methods and accounting methods is minimal (e.g., −2.7% to 4.6%), whereas at lower loads (65%), discrepancies between the methods increase (up to 13.5%). This variability is attributed to combustion instability under reduced loads and limited ability of continuous monitoring systems to capture short-term fluctuations. The accounting method, which provides theoretical estimates, is particularly sensitive to variations in fuel composition and combustion efficiency due to being constrained by the accuracy of emission factors. The primary sources of divergence include: (1) the inherent uncertainty of waste composition, which challenges the theoretical assumptions of the accounting method; (2) the limitations in the quality control of direct measurement methods, coupled with the lack of long-term, highfrequency monitoring data in the waste incineration sector. Despite the aformentioned challenges, a deviation of approximately 10% between accounting values and measured values is currently deemed acceptable. However, with the advancement of monitoring technology, transitioning toward more accurate measurement-based methods is crucial to better reflect actual CO2 emissions. This transformation will improve the reliability of emission data and support the development of robust carbon management frameworks for the waste incineration industry. Conclusion The field CO2 concentration measurements in the municipal solid waste incineration sector show strong consistency between manual and online monitoring methods. Taking manual method as the reference standard, the online method achieves a relative accuracy within 15.0% and relative error within 13.0%, both of which meet the requirements specified in relevant technical standards. Comparative analysis shows that the deviation between manual method and accounting method ranges from −2.7% to 13.5%, while the deviation between online method and accounting method ranges from 1.7% to 10.7%, indicating reasonable comparability among the three methods. The study emphasizes that measurement standards and technical specifications should be served as crucial foundations for implementing China's dual carbon goals. There is an urgent need to establish comprehensive emission monitoring standards that address monitoring technologies, data quality, and standardized protocols to ensure data comparability and credibility across different regions and industries. Recent policy developments have shown significant progress, as evidenced by 2024 technical specification of the Ministry of Ecology Environment of the People's Republic of China for carbon emission trading market in the cement industry, which for the first time explicitly allows key emission units with installed automatic CO2 monitoring equipment to report their CO2 emissions based on monitored data. This represents an official recognition of measurement-based methods from technical perspective. However, the applicability of corresponding policies or standards in other industries, including waste incineration, remains undefined. This study aims to address this gap by systematically evaluating the feasibility of applying measurement-based methods in the waste incineration sector. Considering the practical challenges in obtaining representative fuel and carbon-containing samples, and the feasibility of using measurement-based data to verify accounting method results, this study suggests establishing an industry-specific CO2 emission accounting and verification framework based on actual measurement methods. Such a framework will significantly improve the accuracy and reliability of emission data, provide robust technical support for China's carbon emission management and trading mechanisms, and promote the adoption of advanced monitoring technologies in industrial sectors.

Key words: municipal solid waste incineration, CO2, practical measurement method, accounting method