Methane emissions from coal mining operations have a large global warming effect, and their recovery is only 15–23% in China (14, 15), compared with 35% with more advanced recovery technologies or 60% with the best system available (16). Adopting one or another of these would lower the emission factor from the current 0.24 t CO2-eq t
−1 coal to 0.20 or 0.14. The emission reduction benefit would extend beyond the N fertilizer industry because coal constitutes 70% of the total energy supplies in the entire country (12).