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What is Guano?

By S. Mithra
Updated Mar 05, 2024
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Any excrement from seabirds, seals or bats that has value to humans as fertilizer might be referred to as guano. The term originated in Peru to differentiate useless bird feces from the nutrient-rich droppings of cormorants, pelicans and other sea birds. The word's usage has since been widened to include, especially, the mixture of remains and excrement of bats that collect on the floor of caves.

Economic Benefits

Centuries ago, farmers in South America harvested the white piles of bird droppings from shorelines and islands to use as fertilizer on their crops. The export of guano to Europe became economically beneficial for the farmers. Bat guano also has a long agricultural and economic history in Cuba. In the 21st century, feces from bat caves in the United States, Asia, Cuba and South America is marketed as the some of the best organic fertilizer available.

Chemical Composition

Bat guano is an ideal fertilizer because of its chemical make-up. Rich in nitrogen and phosphorous, it provides important chemicals for crops. It is harvested from deep inside caves, where it is protected from sunlight, rain and wind and doesn't break down as quickly as other organic matter does. When the droppings are exposed to water, the nitrates in them can be washed away, so being protected from rain helps maintain their usefulness. Guano also has beneficial fungi and bacteria that act as a natural fungicide to protect plants from disease.

Organic Fertilizer

Although chemical fertilizers are more widely used by modern farmers, guano remains a key resource for organic farmers, especially those in the United States. Farmers can request a certain color, species of bat or place of origin in addition to requesting a certain chemical composition. Bat droppings are richer than seabird or seal feces, and they are more plentiful. They also are much richer in plant nutrients than the same amount of horse or cow manure is, and they do not have the same pungent odor.

Negative Aspects

Some critics say that the harvesting of bat guano from caves has certain detrimental effects. The process, which is also called mining, disturbs the bats' habitat and can cause them to panic, which can result in the bats dropping their young, not eating or not getting enough rest. It has been blamed for bat populations decreasing in areas where guano is harvested. Removing bat feces from the caves also affects other animal species that rely on the droppings for nutrients.

Frequently Asked Questions

What exactly is guano and where does it come from?

Guano is the accumulated excrement of seabirds, bats, or seals. It is primarily found in regions where these animals congregate in large numbers, such as islands, coastal areas, or caves. Guano is rich in nutrients like nitrogen, phosphate, and potassium, making it a highly valued natural fertilizer that enhances soil fertility and crop yields.

Why is guano considered an important natural resource?

Guano is prized for its high nutrient content, which is essential for plant growth. According to the International Fertilizer Development Center, guano's rich composition of nitrogen, phosphorus, and potassium, along with trace elements, makes it an excellent organic fertilizer. Its use can significantly improve soil quality and increase agricultural productivity without the environmental drawbacks of synthetic fertilizers.

How has guano impacted historical events or economies?

Guano has played a significant role in history, particularly in the 19th century when the Guano Islands Act of 1856 allowed U.S. citizens to take possession of unclaimed islands rich in guano deposits. The guano trade boomed, impacting global agriculture and economies. It even led to conflicts over territory due to its value as a natural resource for agriculture.

What are the environmental concerns associated with guano harvesting?

Guano harvesting can disrupt wildlife habitats and ecosystems. Over-extraction can lead to the destruction of nesting grounds for birds and bats, which are crucial for maintaining ecological balance. Responsible management is necessary to ensure that guano is collected sustainably, preserving both the environment and the species that produce it.

Can guano be used in all types of farming practices?

Guano is versatile and can be used in various farming practices, including organic farming, due to its natural origin. It is particularly beneficial for crops that require rich soil, such as coffee and cacao. However, the application must be managed carefully to avoid nutrient runoff and potential eutrophication of nearby water bodies.

How does the nutrient content of guano compare to synthetic fertilizers?

Guano typically contains higher levels of certain nutrients compared to some synthetic fertilizers. For instance, it can have a nitrogen content of up to 10%, phosphorus up to 14%, and potassium up to 2%, according to the Food and Agriculture Organization. These nutrients are also more slowly released, providing a longer-term benefit to plants and reducing the risk of leaching.

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Discussion Comments

By anon287572 — On Aug 26, 2012

I would say if your relative uses a charcoal respirator and lightly sprays the guano with water so that there is no dust when scooping it up, they should be fine.

By anon76263 — On Apr 09, 2010

Is bat guano harmful to domestic pets?

By anon70567 — On Mar 15, 2010

i'm from Malaysia and working as a part time guano organic fertilizer distributor. Guano that i sell is mixed with effective microorganism. Is it true that guano is hazardous to human life?

By anon60872 — On Jan 16, 2010

Bat Guano or bat poo is used in manufacturing in most mascaras as well. so ladies what do you say we go botanical like Arbonne?

By OMGbuster — On May 06, 2009

let's all just say that this stuff can be highly deadly, but most things you use in farming are highly dangerous. about 30% of all injuries occur in some kind of farming or farm vehicle experiment. it's not that big of a surprise. bats eat poisonous bugs for goodness sake.

By anon30001 — On Apr 12, 2009

My understanding of this fertilizer is ancient in origin and that the Natives of South America had the dung burnt in a special manner, a slow burning process. It was then used as a fertilizer.

A program on this topic aired on Coast to Coast AM with George Nooray.

By anon28705 — On Mar 20, 2009

I work at a hospital in Canada, and I have recently had a patient who developed farmers lung from inhalation of bat dung. Yes, it is very dangerous and yes, you should hire a professional to have it removed.

This particular individual for whom I have cared for will be in the hospital for a long-term period, and if i were you I would not take the chance of cleaning it yourself, because it is not worth the risks associated with exposure to guano.

By ericakayy — On Mar 17, 2009

Can guano be a health hazard?

By deetui — On Mar 03, 2009

are there any chemical reactions regarding guano?

By anon24038 — On Jan 06, 2009

hmm. i was watching a show on youtube, now it is one of those online websites that show minerals and other natural resources... now they were talking about animal by-products and its uses and they said bats by-products known as guano is also asbestos... is this true?

By bigdog13 — On May 01, 2008

I am removing bat guano from a barn for someone. He wants me to spread it in his garden. after reading your article i am not sure if I should. It has been there for a few years i'm sure. I have respirators and suits and gloves for protection. Please let me know if it is OK to put in the garden. Also if too much is bad for the garden.

By anon8854 — On Feb 22, 2008

is it true that energy drink co. use guano in their products that we drink?

By anon6113 — On Dec 16, 2007

Is there really any type of guano bowl?

By violetsky70 — On Sep 13, 2007

After guano has lain around for a couple of years, a fungus can grow in it, releasing spores into the air that cause histoplasmosis in humans. The east and central parts of the U.S. are especially susceptible to the fungus that causes this disease.

Histoplasmosis can cause serious respiratory diseases in humans, causing fever and chest pains. If left untreated, histoplsmosis can turn into a chronic lung disease that resembles tuburculosis. In the very young and the very old, or people who already have cancer, AIDS or other serious illnesses, histoplasmosis can be fatal. Histoplasmosis can also travel from the lungs to the eyes, causing ocular histoplasmosis syndrome, which destroys the central vision (not periphreal). The lung problems can many times be cured with anti-fungal medications, but the ocular disease has no cure.

If bat guano is found in a home or other building, it is important to have it removed as soon as possible by a trained professional. A professional will search for any roosting bats that may be inside, then for any passageways that may be accessible to bats. Any points of entry have to be closed so that the bats do not reappear.

To remove guano, a professional will wear a respirator and dress in protective gear. The guano is usually sprayed with water or a fungicide so that the removal process will not cause the fungus to become airborne. It can then be cleaned up via a specialized vacuum, together with cleaning chemicals, or can be collected manually, or a combination of both.

If bat guano has been found in the house, especially if it has been there for a few years, it is important to watch for any symptoms and to get medical attention if any lung or eye disease symptoms begin. Early treatment is extremely important in the ocular histoplasmosis, as laser treatments can stop the vision loss, though they can not restore any vision that has already been lost.

By anon2925 — On Jul 31, 2007

I have suspicions that there are bats in the chimney in the home I am renting. The fireplace is gas and has not been used for years; glass-enclosed firepit, standard chimney. Concerned there is guano in the firepit. Very interested in comments/responses to the above story.

By anon2501 — On Jul 14, 2007

I have recently found out that I have bats in my attic (since one was found in my kitchen and I nearly went spastic)....

Now, I am being told by the person from Wild Life Control whom I am paying $700 to bat proof the outside of my home (a way for them to get out and not return but only guaranteed for THREE years).

In addition they want $1,200 to clean the bat droppings from the attic area and disinfect it because they are telling me that the

"guano" is cancer causing and as dangerous as asbestos. Is this true? What danger is there in removing this guano, if any? Can this cause lung disease? Should I let the professionals remove it and not allow a family member to do this removal due to danger? I appreciate a reply.

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