Measuring China's energy efficiency by considering forest carbon sequestration and applying a meta dynamic non-radial directional distance function

China is the world's largest consumer of fossil energy and CO2 emitter, as well as the country with the fastest growth of forest cover. While the China government regards forest carbon sequestration as one of the paths to achieve carbon neutrality, the existing research on energy efficiency measurement in China rarely takes it into account. Thus, this research introduces forest carbon sequestration as a new desirable output variable and applies a meta dynamic non-radial directional distance function to measure China's energy efficiency from 2010 to 2019, which effectively improves the accuracy of the assessment while providing dynamic comparison results. Different from previous studies, findings shows that, with the improvement of forest carbon sequestration, the technology gap ratio between the central and western regions and the eastern region has narrowed from 0.4 to 0.23 and 0.36 to 0.2 on average in 2015-2019. In addition, this study obtains the room for improvement of China's provinces in forest carbon sequestration and puts forward policy suggestions for its long-term sustainable development of forest carbon sequestration, including establishing responsibility objectives of annual minimum growth of forest carbon sequestration by provinces, accelerating the construction of forest carbon sequestration trading system, and developing urban green space carbon sequestration.