The extent and fate of fossil carbon accumulation in our technosphere

Energy and non-energy use of fossil carbon-based fuels and associated emissions have been extensively studied, but the retention and accumulation of fossil carbon in the technosphere are less understood. This study uses retrospective dynamic material flow modeling to map the flows related to fossil carbon in durables between the years 1995 and 2019 using monetary multi-regional supply-use tables for 1995–2019 and multi-regional hybrid supply-use tables for 2011. In 2011, 91% of the extracted fossil carbon flowed directly to the atmosphere, with 9% accumulating in the technosphere, primarily in construction, manufacturing, and households. From 1995 to 2019, 8.4 Gt of fossil carbon (i.e., 30.8 Gt of CO₂ equiv) accumulated in all human-made artifacts, with most remaining in use and some ending up in landfills, where decomposition exceeds 50 years. This study lays a critical foundation for future research focused on reducing fossil carbon reliance by curbing its inflow and slowing its throughput in the technosphere.