1/9/2004 · Current estimates of world cement manufacture are of the order of 1.7×10 9 t/year, enough to produce well over 6 km 3 of concrete per year or at least 1 m 3 per person. For the production of each cubic meter of concrete, average CO 2 emissions are about 0.2 t, which amounts to about 0.08 t CO 2 per ton