Peak Phosphorus – Peak Food? The Need to Close the Phosphorus Cycle

Abstract

The peak in the world production of phosphorus has been predicted to occur in 2033, based on world reserves of rock phosphate (URR) reckoned at around 24,000 million tonnes (Mt), with around 18,000 Mt remaining. This figure was reckoned-up to 71,000 Mt, by the USGS, in 2012, but a production maximum during the present century is still highly probable. There are complex issues over what the demand will be for phosphorus in the future, as measured against a rising population (from 7 billion to over 9 billion in 2050), and a greater per capita demand for fertiliser to grow more grain, in part to feed animals and meet a rising demand for meat by a human species that is not merely more populous but more affluent. As a counterweight to this, we may expect that greater efficiencies in the use of phosphorus - including recycling from farms and of human and animal waste - will reduce the per capita demand for phosphate rock. The unseen game changer is peak oil, since phosphate is mined and recovered using machinery powered by liquid fuels refined from crude oil. Hence, peak oil and peak phosphorus might appear as conjoined twins. There is no unequivocal case that we can afford to ignore the likelihood of a supply-demand gap for phosphorus occurring sometime this century, and it would be perilous to do so.

Leaching of Phosphorus and Cadmium in Soils Amended with Different Bone Chars

“…Modern agricultural production greatly relies on costly phosphorus (P) fertilizers from phosphate rock reserves that are being depleted and which may contain potentially toxic elements such as Cd, As, and Pb . P‐recycling from human and animal waste is urgently needed to obtain contaminant‐free P‐fertilizers, preserve P‐reserves, and avoid future crises of P‐fertilizer scarcity . Bone chars (BC) are beneficial soil amendments for safe, clean and sustainable crop production .…”

Endangered elements, critical raw materials and conflict minerals

“…20,21 Peaking, as in ‘peak oil’, does not mean the point of running out of something, but where the production rate reaches its maximum level, and thenceforth, that the output of a given material (from the particular source being evaluated) can be expected to decline relentlessly, the material eventually becoming scarce. 30 The concept of the ‘burn-off time’ has been introduced, 20–22 which has the same formal definition as the R/P ratio; however, it has been emphasised that, while this is applicable in a stagnant economy (constant production rate), in a growing economy, it overestimates the production lifetime. 20,21 From a pragmatic perspective, a low R/P value can be taken to draw attention to an element or raw material which might become scarce in the not too distant future, or whose production might prove difficult to enlarge sufficiently to meet rising demand from the expansion of new technologies.…”

“…The supply of phosphorus is a much debated and complex topic, but a production peak at some point during the present century is possible, 30 with potentially very serious consequences for industrialised agriculture. 30 It has also been determined that the global area of tilled soils peaked in 2005, while global fish production peaked in 2002–2003, with the alarming forecast that, by 2060, the fish catch will have decreased to just 10% of its maximum level. 20,21 Such factors as limited provisions of phosphorus and soil to grow food, along with falling fish catches, are likely to restrict global food supplies and therefore set limits to world population.…”

“…By way of a substitution strategy, 22 it is for example, possible to make pin-head capacitors in mobile phones from aluminium, to replace the yttrium, tantalum or hafnium, that they are currently made from; while silicon, silicon carbide or carbon nanotubes might be used to make transistors that are currently made from germanium and indium; and it has been found that silicon/polyvinyl chloride can be employed to make solar cells that have twice the energy conversion efficiency of thin-film cells based on indium and gallium. 22 Nothing, however, can replace phosphorus, which is required by all living organisms, 30 and the proposed recovery of phosphorus from seawater would most likely fail due to the necessarily very large energy inputs required to produce it on the scale that it is consumed globally. 29 It appears that production peaks will occur on the longer timescale, first in mining and producing from high grade reserves, followed by that from low grade, and finally from the ultralow grade reserves.…”

“…29 It appears that production peaks will occur on the longer timescale, first in mining and producing from high grade reserves, followed by that from low grade, and finally from the ultralow grade reserves. 30,48 Hence, if we wish to maintain its overall supply, it may be necessary to recover phosphorus from animal and indeed human waste (Figure 6). 30 There are complex issues over what the demand will be for phosphorus in the future, as measured against a rising population 25 (from 7 billion to over 9 billion in 2050), and a greater per capita demand for fertiliser to grow more grain, in part to feed animals and meet a rising demand for meat by a human species that is not merely more populous but more affluent.…”