Critical Review of Climate and Resource Costs and Benefits of Machinery and Equipment

Environmental input–output analysis suggests that we use one-third of all metals to produce machinery and equipment (ME) and that their production causes 5% of global greenhouse gas emissions globally. Yet, our empirical understanding of material use and emissions associated with ME remains limited, making it the least researched major aspect of material consumption. Machines are not represented explicitly in climate change mitigation models and there is little research considering mitigation opportunities related to ME. Meanwhile the practice and potential for circular material flows, which have dynamic interactions with machinery, have yet to be explored. ME is a very diverse category and so the use of economic statistics and input–output models are essential for a holistic understanding. Mitigation, however, can only be understood through bottom-up engineering research. We identify data sources for future empirical research and suggest how to combine these. Future demand for ME can in part be foreseen by assuming that lower-income countries will use machines to increase their productivity to levels seen in high-income countries. Additional demand will arise from the introduction of autonomous machines, service robots, and artificial intelligence in workplaces and homes. We describe knowledge gaps and outline research questions important for anticipating the future requirements for machines and their potential contributions as both causes of and solutions to climate change and resource overconsumption.