CO2 emission Technology: general issues 9 climate change 4 energy efficiency 4 sustainability 4 China 3 History of engineering & technology 3 Research & information: general 3 biochar 3 biomass 3 circular economy 3 life cycle assessment 3 optimization 3 renewable energy 3 simulation 3 temperature 3 CO2 emissions 2 DEA 2 LCA 2 Saharan dust 2 adsorption 2 air quality 2 bioenergy 2 climate change mitigation 2 crop production 2 deterioration 2 digestate 2 economic analysis 2 economic growth 2 energy transition 2