As an adsorbent material, porous carbon (PC) with high specific surface area, renewability and excellent thermal stability has been certified to be a potential candidate for carbon dioxide (CO2) adsorption. However, its high manufacturing cost and insufficient CO2 adsorption capacity are still significant problems to be solved urgently. The present work reported a nitrogen-doped porous carbon (NPC) synthesized from hazardous waste oil sludge (OS) via a facile and low-cost approach. The NPC possessed favorable features for excellent adsorbent, such as outstanding specific surface area (1224 m(2).g(-1)), large pore volume (1.738 cm(3).g(-1)) as well as tunable and large range of pore size distribution, among which the specific surface area and pore volume of porous carbon (PC) were just 632 m(2).g(-1) and 0.826 cm(3).g(-1), respectively. The carbon material NPC prepared by mixing oil sludge pyrolysis char with KOH and urea at 700 degrees C achieved the formation of nitrogen-containing functional groups, with CO2 adsorption capacity as high as 3 mmol.g(-1). Furthermore, NPC possessed excellent reproducibility and thermal stability. It is demonstrated that the NPC synthesized from OS via a facile and low-cost approach was a promising adsorbent material for CO2 capture. This work provides a new strategy for synergetic processing of hazardous industrial waste and greenhouse gas.