Guano

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For other uses, see Guano (disambiguation).

Guano (from the Quechua 'wanu', via Spanish) is the name given to the collected droppings of seabirds, bats, and seals [1]. It is highly prized as an effective fertilizer or gunpowder ingredient due to its high levels of phosphorus and nitrogen. Superphosphate made from guano is used for aerial topdressing. Soil that is deficient in organic matter can be made much more productive by addition of this manure. Guano consists of ammonia, along with uric, phosphoric, oxalic, and carbonic acids, as well as some earth salts and impurities. The high concentration of nitrates also made guano an important strategic commodity; in fact, the War of the Pacific between the Peru-Bolivia alliance and Chile was primarily based upon Bolivia's attempt to tax Chilean guano harvesters.

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The ideal type of guano is found where there is little rainfall and exceptionally dry climates, as the rainwater drains the guano of nitrates. Guano is harvested on various islands in the Pacific Ocean (for example the Chincha Islands and Nauru) and in other oceans (for example Juan de Nova Island). These islands have been home to mass seabird colonies for many centuries, and the guano has collected to a depth of many metres. In the 19th century, Peru was famous for its supply of guano which was treated like gold. Bat guano is usually mined in caves. One of the major innovators in guano harvesting was Benjamin Drake Van Wissen.

Guano has been harvested over several centuries along the coast of Peru, where islands and rocky shores have been sheltered from humans and predators and administered by private and state companies. The Guanay Cormorant has historically been the most important producer of guano; its guano also tends to be more rich in nitrogen than guano from other seabirds. Other important guano producing species off the coast of Peru are the Peruvian Pelican and the Peruvian Booby.

[edit] Fertilizer

It is estimated that there is only enough phosphorus from current resources to last about 30 years. This is a problem as vast volumes of phosphorus are needed to produce fertilizer, as it is an essential plant macronutrient. Guano is rich in phosphorus and is an effective phosphorus fertilizer. Use of guano for this purpose will undoubtably increase as phosphorus, from traditional mined resources, becomes more scarce and thus more expensive. It is a $1.4 billion industry.