Comparative assessment of radiocarbon and balance method for determining biogenic and fossil CO2 emissions from waste-to-energy plants in Austria and China.

Accurate quantification of biogenic and fossil CO2 emissions from waste-to-energy (WtE) plants is essential for greenhouse gas (GHG) reporting and emissions trading. This study compares two standardized methods - the Radiocarbon Method (ISO 13833) and the Balance Method (ISO 18466) - based on extensive sampling campaigns at three Austrian and one Chinese WtE facility. The Radiocarbon Method determines the biogenic CO2 share via 14C analysis of flue gas, while the Balance Method derives biogenic and fossil fractions through coupled mass- and energy-balance modeling. Across all facilities, both methods yielded highly consistent results for biogenic CO2 shares, ranging from 55 to 64% for the Austrian plants and 53-63% for the Chinese plant. Fossil CO2 emission factors ranged from 320-470 kg CO2 t-1 waste in Austria and 340-370 kg CO2 t-1 waste in China, closely matching literature data. However, deviations in absolute fossil CO2 masses of up to several thousand tonnes per year were observed, mainly due to uncertainties in flue gas volume measurement. Energy-balance-based reconciliation in the Balance Method significantly reduced such discrepancies. Extrapolated over annual operation, measurement inconsistencies could affect reported annual fossil CO2 emissions by several thousand tonnes, corresponding to economic deviations of several hundred thousand euros or yuan in CO2 certificates. The study confirms the applicability of both approaches under different waste and plant conditions and emphasizes the Balance Method's potential as a reliable, continuous monitoring tool for integrating WtE into carbon accounting frameworks.