Does Land Operation Scale Improve Rice Carbon Emission Productivity? Evidence from 916 Farmers in Guangdong Province, China

China aims to reduce carbon emissions but faces challenges from small-scale farmer operations. Previous studies have predominantly examined carbon density using macro-level data. This study employs a primary field survey involving 916 rice farmers, along with input–output data from their typical paddy plots, to calculate micro-level carbon emissions and assess the impact of land operation scale. The results indicate that operational scale enhances carbon emission productivity and has a nonlinear relationship with carbon emission intensity. From survey data, the carbon emission intensity of late rice is 4648.77 kg CO2eq·ha−1 in Guangdong province China, which differs by a mere 1.14% from the figure derived from yearbook macro data. The yield carbon emission productivity and yield value carbon emission productivity of rice production are 1.347 kg·kg CO2eq−1 and 2.166 CNY·kg CO2eq−1, respectively. The operational scale significantly positively enhances indirect carbon emission productivity, a key indicator of economic growth and environmental sustainability. However, it exhibits a U-shaped effect on carbon emission intensity. Our results underscore the critical role of expanding the operational scale among individual farmers to boost carbon emission productivity, facilitating the simultaneous development of grain crops and a reduction in carbon emissions.