Environmental Engineering Reference
In-Depth Information
Not available
Algeria
2009
2011
Even old estimates put
Morocco in the lead
China
Jordan
Morocco/
Western Sahara
Russia
South Africa
Previously overlooked
geological reports
from the 1980s
bumped up estimates
Syria
United States
Other
0
10
20
30
40
50
Phosphate rock reserves (billion tonnes)
FIGURE 8.3
Global distribution of world phosphate rock reserves (in billion metric tons, BMT). Blue indicates
the assessment of USGS in 2009 and the purple indicates the adjustment made by Van Kauwenbergh (2010) after
comprehensive analysis of available industry and government reports, gray literature, and published studies. It is
important to note that a “reserve” is a geological deposit of a material that can be economically and legally
extracted or produced at the time of the determination. The USGS has now adopted the new estimates in its offi-
cial phosphate reports. (Reprinted from
Elser and Bennett 2011
.)
larger source of P than weathering to the world's soils. Large deposits of mineable apatite
are located in China, Morocco, South Africa, Jordan, and parts of the United States
(
Figure 8.3
). These five countries control approximately 85% of the P mined globally, with
implications for geopolitical stability. There are ongoing debates about the amount of
P remaining in reserves (
Box 8.2
).
Figure 8.4
shows the amount of P “leakage” or waste that occurs as it moves through
the food system from mined phosphate rock to human waste. Of all P mined for food
production, only one-fifth is consumed by people (
Cordell et al. 2009
). Along the way, 8
million tonnes are lost in erosion from agricultural land each year, and 7 million tonnes in
runoff from animal manure. About 3 million tonnes are forgone in crop losses (e.g., wild
animal consumption, disease). There are postharvest losses, too: 0.2 million tonnes before
crops become food products, 1 million tonnes in food chain losses (including distribution,
retail, and household losses), and 2.7 million tonnes lost as landfill or sewage.
People have also altered the transfer of P around the world in products such as
fertilizers, animal feed crops, and food crops. We remove P from mines in only a few
places, spread it around the world on agricultural soils, then trade the crops produced
using—and now containing the P from—those fertilizers. While global crop production
has nearly tripled over the past 50 years, crop trade has increased much more rapidly
(and the quantity of P in traded crops increased more than six-fold for most countries
over this same time period;
Schipanski and Bennett 2012
). Because a large fraction of
traded crops are destined for livestock feed and most P consumed by livestock ends up in
