Keeping the annual mining rate of about 19.5 MMT P yr- constant, the world's known phosphate reserves could be exhausted in about 120 years. Moreover, it has been projected that the utilization trend is unlikely to decline in next 30 years. It will instead probably increase at the rate of 0.7-1.3% annually. This strongly suggests that phosphate rock, as a finite nonrenewable resource, may be exhausted in a much shorter time. It has been shown that the global average phosphorus content in raw ores dropped to 29.5% in 1996 from 32.7% in 1980, and that global reserves can sustain the current mining intensity for only another 80 years. Some phosphorus-rich deposits around the world can be exploited much sooner. China's phosphorus reserves, for instance, constitute 26% of the world's total reserve base, second only to Morocco and the Western Sahara. With a high intensive extraction activity as well as losses incurred during mining, the basic reserve of the nation's phosphorus resources, that is, 4054 million tons with average P2O5 content of 17-22%, could be exhausted in 64-83 years. Certainly, the larger reserve base and probably more reserves to be discovered in the future guarantee a longer lifespan of the extraction. Even so, the deposits of phosphorus in the lithosphere will inevitably be depleted before new igneous or sedimentary rocks to be formed via the biogeochemical process at the time-scale of millions of years.
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