Fossil energy saving and CO2 emissions reduction performance, and dynamic change in performance considering renewable energy input

Energy environmental and non-radial Malmquist indexes are proposed employing a non-radial directional distance function to evaluate fossil energy saving and CO2 emissions reduction performance, and dynamic change in performance internationally. Renewable energy is also proposed as an essential energy input for the models. An empirical study of 26 Organization for Economic Cooperation and Development countries and Brazil, Russia, India, and China was performed, with the following outcomes: fossil energy saving and CO2 emissions reduction performance is underestimated for most countries, regardless of renewable energy input, however, this underestimation has little influence on performance rankings; there is no significant correlation between the proportion of renewable energy consumption and fossil energy saving and CO2 emissions reduction performance; the 30 countries can be divided into four categories with corresponding specific strategies for energy saving and emissions reduction; Generally, technological progress and efficiency improvement are out of sync, mainly because of the difficulty to achieve the efficiency improvements.