Abstract
Environmental impact assessments of machinery and equipment (ME) are constrained by process-based life cycle assessment (LCA) with limited system coverage and by aggregated top-down models with reduced representativeness. Lack of knowledge about consistency across these approaches hampers the understanding of ME impacts and policy making. This study quantifies greenhouse gas emission multipliers (cradle-to-gate emissions per unit production) of ME using data from process LCA (ecoinvent), national environmentally extended input-output (EEIO) models, and a multiregional EEIO model (EXIOBASE) for the United States, China, Japan, and South Korea, assessing variations, reliability, and compatibility. While EXIOBASE (seven ME sectors) and national EEIO data (32-102 sectors) broadly align, national EEIO models differ more in production technologies, with deviations from 100-fold lower to 3.7-fold higher than EXIOBASE results. Ecoinvent offers broad ME product-level coverage (∼390 sectors), especially for general and electrical ME, but with uneven representation and limited geographic differentiation. Its multipliers vary widely and often exceed EXIOBASE values, challenging the assumption that process-based LCA underestimates impacts due to truncation. Overall, our results reveal cross-model variation, confirm the relative reliability of EEIO data, point to limitations in ecoinvent, and underscore the need to link technical detail with global trade representation in ME modeling.