When eggshells were present, the CES compost raised the soil pH to values higher than 6 and reduced
the soil mobile fraction for both Pb and Zn, in more than 95%. Soil toxicity towards Vibrio fischeri was also
suppressed and environmental risk decreased to “low level”. However, the immobilisation in the acid
insoluble soil component was significantly achieved only for Zn. In addition, regarding soil carbon dynamics
the CO2eC emissions were enhanced, mainly in the case of the highest rate of amendment. Both
first order-E and parallel first order models may adequately describe the kinetic data of CO2eC cumulative
release. Without eggshells, the CWES compost revealed limited effect on heavy metals immobilisation,
likely due to its small capacity to correct soil acidity, at lower application rates. Using solely
eggshells, the ES waste had similar outcomes when compared with CES, but at the higher application
rate, CO2 emissions were enhanced with the eggshell compost due to the contribution of biotic carbon
present therein. Therefore, this study points out that CES is an effective liming material and may be used
for in situ remediation of contaminated soil with Pb and Zn.