Carbon dioxide emissions from overburden fertilised with sewage sludge in the reclamation process was studied. A greenhouse pot experiment was conducted in the third and fourth year of a six-year research cycle. Samples of overburden, taken at a gravel-pit in Żabi Róg, and samples of sewage sludge obtained from the Municipal Wastewater Treatment Plant in Olsztyn were combined at a ratio of 75 to 25% and 50 to 50%. A mixture of grasses was grown in pots. During the growing season, samples of overburden soil were brought to a moisture content of 40, 60 and 80% of the maximum water-holding capacity, put into tightly sealed jars with NaOH, placed in a phytotron and incubated at 10, 20 and 30ºC. Carbon dioxide emissions were determined according to the modified ISERMEYER method. The results of the study were verified statistically. It was found that incubation temperature had the most significant effect on CO2 emissions, which reached the highest level on the first day and decreased approximately 2- to 2.6-fold on the second and third day respectively. A rise in temperature to 20ºC and 30ºC increased carbon dioxide emissions by 133% and 296% respectively, relative to the initial temperature of 10ºC. Sludge dose also contributed to a significant increase in CO2 emissions, but this increase was around twofold lower, compared to that caused by temperature. Carbon dioxide emissions were affected by the moisture content of overburden to a much lower degree, and only a moisture content equal to 80% of the maximum water-holding capacity was found to exert a statistically significant effect. An analysis of correlation revealed a highly significant effect of temperature on CO2 emissions (r = 0.78), a less significant effect of sludge dose (r = 0.46), and a slight negative effect of moisture content (r = –0.01).