Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Are we going to run out of phosphorous?, published by John G. Halstead on December 7, 2021 on The Effective Altruism Forum.
I have recently looked into the threat of 'peak phosphorous' and thought I would quickly share my findings, as phosphorous is arguably one of the more plausible 'peak resource theories'. I conclude that the risk of phosphorous depletion to global food security are minimal.
‘Peak phosphorous’ is one of the more popular ‘peak resource’ theories, along with ‘peak oil’.[1] Phosphorous is essential for food production, and has no substitutes. Organic sources of phosphorous, such as crop residues, food waste, excreta, are classed as renewable. Phosphate rock on the other hand is classed as non-renewable and finite because it cycles from the lithosphere to the hydrosphere at rates of millions of years. When they are used in agriculture, phosphorous molecules are not being destroyed, they are just being redistributed around the world.[2] But still rock phosphate is, for practical purposes, finite because, once used, it cannot feasibly be retrieved for millions of years, at least at reasonable energetic cost.
Since supplies of phosphorous rock are finite, many argue that if current consumption continues, unless remedial action is taken, phosphorous use will peak in the next few decades, which might threaten global food security or even lead to global catastrophe.[3]
Before we discuss this, when considering peak resource theories, it is important to define the difference between reserves and resources (USGS p195):
Resource = A concentration of naturally occurring phosphate material in such a form or amount that economic extraction of a product is currently or potentially feasible
Reserve base = The part of an identified resource that meets minimum criteria related to current mining and production practices including grade, quality, thickness and depth.
Reserve = The part of the reserve base which can be economically extracted or produced at the time of the determination. This may be termed marginal, inferred or inferred marginal reserves. This does not signify that the extraction facilities are in place or functional.
On this definition, reserves are a dynamic figure: they will change depending on demand, scarcity and market prices. If scarcity increases, then the price will increase, producers will have greater incentive to find and exploit new reserves, and consumers will have incentives to economise on consumption or to recycle.
Resources are also dynamic as we might discover new deposits that we did not previously know about.
As we would expect, reserves of phosphorous change significantly all the time. In 2020, the US Geological Survey estimated that phosphorous reserves were 71 billion tons (p123), up from 16 billion tons in 2010 (p119).
In 2020, consumption of phosphate was 47 million tonnes. At current rates of consumption, it would take 1,500 years to use up the world’s phosphorous reserves, on the (false) assumption that reserves will remain static. According to the US Geological Survey, phosphate rock resources are 300 billion tons. So, at current rates of consumption, it would take more than 6,000 years to use up all phosphorous resources.
Moreover, there is ample scope for improvement in the efficiency of consumption of phosphorous.
As this shows, despite huge increases in food yields, phosphate consumption has been flat in North America since 1970 and declined dramatically in Europe since 1987.
Fertiliser use in low and middle-income countries is much less efficient than in rich countries. Li et al (2015) estimate that in China 2.2kg of phosphorous per hectare was lost in crop and animal production systems, compared to rates of 0.4kg per hectare in Sweden and 0.5kg per hectare in the UK and Ireland.[4] This suggests that fivefold phosphorous...
