and the related air pollution, including the release of the greenhouse gas carbon dioxide, dioxin, , , and particulates. Production of Portland cement contributes about 10% of world carbon dioxide emissions. The International Energy Agency has estimated that cement production will increase by between 12 and 23% by 2050 to meet the needs of the world's growing population. There are several ongoing researches targeting a suitable replacement of Portland cement by supplementary cementitious materials. Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants, from the Centers for Disease Control, states: An independent research effort of AEA Technology to identify critical issues for the cement industry today concluded the most important environment, health and safety performance issues facing the cement industry are atmospheric releases (including greenhouse gas emissions, dioxin, , , and particulates), accidents, and worker exposure to dust. The associated with Portland cement manufacture comes mainly from four sources: Overall, with nuclear or hydroelectric power, and efficient manufacturing, generation can be reduced to per kg cement, but can be twice as high. The thrust of innovation for the future is to reduce sources 1 and 2 by modification of the chemistry of cement, by the use of wastes, and by adopting more efficient processes. Although cement manufacturing is clearly a very large emitter, concrete (of which cement makes up about 15%) compares quite favourably with other modern building systems in this regard.. Traditional materials such as lime based mortars as well as timber and earth based construction methods emit significantly less . Cement plants used for waste disposal or processing Due to the high temperatures inside cement kilns, combined with the oxidising (oxygen-rich) atmosphere and long residence times, cement kilns are used as a processing option for various types of waste streams; indeed, they efficiently destroy many hazardous organic compounds. The waste streams also often contain combustible materials which allow the substitution of part of the fossil fuel normally used in the process. Waste materials used in cement kilns as a fuel supplement: Car and truck tires – steel belts are easily tolerated in the kilns Paint sludge from automobile industries Waste solvents and lubricants Meat and bone meal – slaughterhouse waste due to bovine spongiform encephalopathy contamination concerns Waste plastics Sewage sludge Rice hulls Sugarcane waste Used wooden railroad ties (railway sleepers) Spent cell liner from the aluminium smelting industry (also called spent pot liner) Portland cement