sustainability Research & information: general 62 Technology: general issues 58 sustainable development 43 History of engineering & technology 36 circular economy 31 climate change 31 renewable energy 24 optimization 23 energy efficiency 22 Biology, life sciences 20 innovation 19 machine learning 19 COVID-19 18 Technology, engineering, agriculture 15 biomass 15 life cycle assessment 15 China 14 Humanities 14 simulation 14 environment 13 food security 13 education 12 efficiency 12 resilience 12 bioenergy 11 energy 11 mechanical properties 11 performance 11 recycling 11