Peak phosphorus

24 03 2009

You have no doubt heard of peak oil. The point at which the rate of oil production begins to decline. Well there’s another peak you should be concerned about if you like to eat food grown in fertilised soil, like much of the world’s population does. Phosphate is a non-renewable resource and is therefore not created on a timescale meaningful to people. This presents us with a bit of a problem because we are using a lot of it and it could potentially run out within the next 50-100 years, having enormous consequences for global food supply and geopolitics. But, its demise could improve the condition of our rivers, lakes, seas and oceans.

A recent paper published in the journal Global Environmental Change titled “The story of phosphorus: Global food security and food for thought” has explored the phosphate dilemma. Here are some of its main points.

Food production is fundamental to our existence, yet we are using up the world’s supply of phosphorus, a critical ingredient in growing food.

Phosphate rock reserves are in the control of only a handful of countries (mainly Morocco, China and the US), and thus subject to international political influence. Morocco has a near monopoly on Western Sahara’s reserves, China is drastically reducing exports to secure domestic supply, US has less than 30 years left of supplies, while Western Europe and India are totally dependent on imports.

Existing rock phosphate reserves could be exhausted in the next 50–100 years.

The demand for phosphorus is predicted to increase by 50– 100% by 2050 with increased global demand for food and changing diets.

The need to address the issue of limited phosphorus availability has not been widely recognized.

As well as the problem of eutrophication due to the leakage of excess phosphorus into waterways, the production of fertilizers from rock phosphate involves significant carbon emissions, radioactive by-products and heavy metal pollutants.

The peak in global phosphorus production could occur by 2033.

Phosphorus can be recovered from the food production and consumption system and reused as a fertilizer either directly or after intermediate processing. These recovery measures include: ploughing crop residues back into the soil; composting food waste from households, food processing plants and food retailers; and using human and animal excreta. Such sources are renewable and are typically available locally.

Fertilizing urban agriculture with phosphorus recovered from organic urban waste could be a significant step towards reaching the Millennium Development Goals on eradicating hunger and poverty, and providing access to safe sanitation.

Shifting to a vegetarian diet, combined with reducing over-consumption, would be one of the most cost-effective measures to reduce agricultural resource inputs (including water, energy, land and fertilizers) and would also minimize greenhouse gas emissions and other forms of pollution.

+ organic farming, permaculture and ending capitalism (an unlikely suggestion in a mainstream academic journal).