Peak Phosphorus

Phosphorus Matters

Compost, Food Shortages, Soil Composition, Soil Conservation, Soil Erosion & Contamination — by Marcin Gerwin

Part One: Closing the Phosphorus Cycle

NOTE: I have gone on about this in other threads, but this actually comes up with the numbers, and much more.  MUST READ.  Go to the source for the entire read.

Matrix. 

It might sound ridiculous, but for every container of bananas, coffee, tea or cocoa imported, we should send back a shipment of a fluffy, earth-like smelling compost. Why is that? With each container of food we import nutrients taken up by plants from the soil. We import calcium, potassium, magnesium, boron, iron, zinc, molybdenum, copper and many others. One of the essential elements imported in food is phosphorus. For every ton of bananas we import 0.3 kg of phosphorus, for every ton of cocoa it’s 5 kg and for ton of coffee it’s 3.3 kg of phosphorus. Tea is a bit more complicated, because the amount of phosphorus depends on the origin of tea - for example in 1 ton of tea leaves harvested in Sri Lanka there are some 3.5 kg of phosphorus, while tea from South India contains 6.6 kg of phosphorus (1).

digg_url = http://permaculture.org.au/2009/01/14/ph...
 
reddit_url="http://permaculture.org.au/2009/01/14/phosphorus-matters/"Each year some 13.5 million tons of bananas alone are exported around the world (2), containing 4,000,000 kg of elemental phosphorus up taken by the plants from tropical soils. And most of this phosphorus never comes back to the soil it was removed from. Yes, but can’t the farmers replace the nutrients lost using fertilizers? That’s what the fertilizers are used for, are they not? Sure they can. Farmers can buy a bag of ground phosphate rocks or guano (bird or bat droppings) or even a bag of artificial fertilizer such as superphosphate if they don’t farm organically. No problem. They can replace every kilogram of phosphorus taken from the soil by plants and sent overseas with their produce.

So, why should we send compost back on ships? This would add extra cost to the imported food and make it much more expensive! We should start closing nutrients cycle soon, because the world reserves of phosphate rocks, which are used for the production of phosphate fertilizers, are declining. They can be depleted even this century

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Closing the nutrients cycle

Ideally the same amount of nutrients that left the farm should come back to it. To achieve this goal we should compost or ferment all residues from farms, food processing plants and households and make them available for farmers. And yes, we need to compost urine and feces as well. There are many types of compost toilets, including the simplest sawdust toilet to the commercial types with electric fans. If handled properly they don’t smell badly and the final product of the compost toilet is just a plain ordinary compost. It can be collected in the city in special containers, standing along the curb near the containers for recycling glass and plastics. Joseph Jenkins’ “Humanure Handbook” is a great resource on the subject.

All organic waste can be collected as a part of a municipality recycling program and leftovers from the kitchen can be picked up weekly from the separate curbside container. For backyard gardeners and farmers who eat their own food there are many methods of composting to choose from – buckets, triangle cages, compost tumblers, worm composting, loose heaps or classic wooden containers. There are even composters which can be kept directly in the kitchen without any suspicious smells.

It seems also a good idea to extract carbon and hydrogen from the food residues in the form of biogas which is primarily methane (CH4). It can be used for cooking, heating, electricity generation or for powering vehicles. The exciting thing about biogas is that we don’t waste any of the minerals from the organic matter - carbon is taken by plants from the air in the form of carbon dioxide and hydrogen comes from water. After fermentation process in a biodigester the organic matter is still perfectly useful as a fertilizer.

If the resources of phosphate rocks become depleted this organic waste recycling program will be crucial for farmers. They will be able to buy or receive finished compost according to the amount of food they sold. It may sound absurd, but the content of phosphorus or other nutrients in crops may eventually be counted in the future, so that we can determine how much compost the farmer should receive. Ideally local food should be involved in this scheme to minimize transport needs. And what about the food from overseas farms like coffee or tea? Well, things get much more complicated here. Theoretically, we could exchange nutrients in the form of food, so that for every kilogram of coffee would send back wheat or barley with the equal content of phosphorus. What farmers can do now is to bring compost from the cities, where people eat imported food. The other option is sending compost back. Hmm… Wouldn’t it be just perfect to have a village scale economy where all nutrients would circulate without cars, trucks, cargo ships and complex municipality programs?

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