Stable isotope evidence for the atmospheric origin of CO2 involved in carbonation of MSWI bottom ash

Stable isotopes were used to constrain the origin of CO2 involved in the ageing process of municipal solid waste incineration (MSWI) bottom ash under open-air conditions. The delta 13C and delta 18O values of CaCO3 occurring in MSWI bottom ash samples of variable age and the delta 13C of the residual organic matter content were measured, and laboratory assessments made of the isotopic fractionation accompanying CaCO3 neo-formation during accelerated carbonation experiments of bottom ash or pure lime with atmospheric or industrial CO2. The results indicate that stable isotopic compositions exhibited by fresh and aged bottom ash samples reflect non-equilibrium processes resembling those described in the carbonation of concrete and mortar. They also lead to conclusions on the prevalent involvement of atmospheric CO2 in the open-air carbonation of MSWI bottom ash.