Peak phosphorus is the next big environmental challenge after peak oil and clean water. Peak phosphorus – when phosphate rock, the only source of phosphorus for agricultural fertilisers begins running out – may only be 25 years away.
New sources of phosphate rock may be found under the Atlantic and Pacific Oceans, and in outback Western Australia, but environmentalists say these are likely to be highly energy intensive to mine and process, lower in quality and higher in radioactive waste than current phosphate rock stocks.
They are still a non-renewable resource.
Peak Phosphorus researcher, Dana Cordell, of Australia’s Institute For Sustainable Futures and Department of Water and Environmental Studies, Linkoping University, Sweden, says it’s preferable to reduce demand on phosphate rock by reusing phosphorus locked up in the soil, and stored in food waste and human excreta.
Her paper, "The Story of Phosphorus: Global Food Security and Food For Thought", will be published in the journal, Global Environmental Change. She has also contributed to a Sustainable Phosphorus Futures website.
Phosphorus Vital for Food Production
Plants create food by photosynthesis, using the sun’s energy to transform CO2 into carbohydrates. Animals eat plants, and animals eat other animals along the food chain, with humans and carnivores at the top.
The missing link is phosphorus, a chemical element necessary for plant growth, and only available to plants through phosphorus in the soil, deposited after millions of years by the breakdown of phosphate rocks, or by the application of phosphorus containing fertilisers.
The amount of phosphorus required to make a kilogram of food varies in inverse proportion to its position on the food chain. A kilogram of prime grain fed beef takes 5 kilograms of grain to produce. One-third of croplands worldwide are now used to produce food for meat animals.
Phosphorus Locked in the Soil and Stored in Food
Humans need only about 0.4 kg of phosphorus each per year, yet because of losses between the soil and what ends on our plate, 22.5 kg of phosphate rock is mined for each person.
Of the millions of tonnes of phosphorus applied to fields and paddocks every year, only 20% makes it onto dinner plates.
Much of the phosphorus is locked in the soil, in a form that plants can’t use, but a huge 50% is lost in production and storage processes between the paddock and the plate.
Food Scraps Waste Phosphorus
Then, if not all the food on the plate, or stored in the fridge is eaten, and is thrown in the trash or down the waste disposal unit, that phosphorus is lost to landfill
Ms Cordell says consumers should be aware of the issue of phosphorus in their food, and of the importance of not wasting food.
Huge amounts of food are thrown away every day from households buying too much food and throwing out what isn’t eaten, restaurants and fast food chains throwing out uneaten food from plates and food scraps from preparation, supermarkets binning less than perfect vegetables and fruit and products past their use by/best by date.
Phosphorus, water, energy and food dollars can all be saved by cooking and eating more economically – using cheaper cuts of meat, all the edible parts of fruit and vegetables, making conserves and pickles from less than perfect produce. Food scraps can be composted, fed to worm farms, and the results put on vegetable gardens to grow more food cheaply.
See also: Ten Tips for Greening Ypur Garden
Sue Cartledge - I'm a science, health, nutrition and lifestyle journalist, fascinated by the way the physical world operates in all its forms, and how ...
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