Risk assessment of nano-scale solid carbon sourced from a CO2-free hydrogen manufacturer used at a steel plant and disposed at a landfill site

A screening assessment of the human health risk from nanocarbon materials, which are solid carbon species produced in carbon-free hydrogen production by methane decomposition, was conducted during the life cycle stages of steel utilization and landfill disposal. First, the scenario was established for the use in the steel industry of a substantial amount of nano-scale solid carbon as an alternative to pulverized coal injected into the blast furnace. Additionally, the scenario was set for landfill disposal of solid carbon. For these scenarios, atmospheric emission quantities during loading and unloading and during storage of solid carbon were estimated using existing emission scenario documents. The atmospheric concentration of solid carbon was estimated using a low-rise industrial source dispersion model. Finally, human health risks were evaluated and compared with the general environmental threshold of carbon nanomaterials in the surrounding area. The results indicated that the atmospheric concentrations of solid carbon around the steel plant and the landfill site did not exceed the environmental threshold by implementing possible emission reduction measures.