Bags filled with bat guano are seen outside of a bat cave at Wat Khao Chong Phran in Ratchaburi, Thailand March 14, 2020. Picture taken March 14, 2020. REUTERS/Juarawee Kittisilpa 

Professor Patrick Onyango holds a black rhino excrement at the Ruma National park, Nyanza province, western Kenya, January 30, 2020. Picture taken January 30, 2020. REUTERS/Baz Ratner 

Test tubes containing samples of black rhinos' excrements are seen at the Zoology lab of the Maseno University, in Maseno, western Kenya, January 30, 2020. Picture taken January 30, 2020. REUTERS/Baz Ratner 

PhD student Collins Kipkorir Kebeni holds a petri dish containing samples of black rhinos' excrements at the Zoology lab of the Maseno University, in Maseno, western Kenya, January 30, 2020. Picture taken January 30, 2020. REUTERS/Baz Ratner 

PhD student Collins Kipkorir Kebeni holds a test tube containing samples of black rhinos' excrements are seen at the Zoology lab of the Maseno University, in Maseno, western Kenya, January 30, 2020. Picture taken January 30, 2020. REUTERS/Baz Ratner 

PhD student Collins Kipkorir Kebeni collects specimens from black rhinos' excrements in the Ruma National park, Nyanza province, western Kenya, January 30, 2020. Picture taken January 30, 2020. REUTERS/Baz Ratner 

Climate change activists of Extinction Rebellion hold banners after unloading a truck filled with horse excrements in front of U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce 

Climate change activists of Extinction Rebellion unload a truck filled with horse excrements, in front of U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce 

Climate change activists of Extinction Rebellion hold a banner after unloading a truck filled with horse excrements in front of U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce 

Climate change activists of Extinction Rebellion unload a truck filled with horse excrements, in front of U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce 

Climate change activists of Extinction Rebellion unload a truck filled with horse excrements, in front of U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce 

Climate change activists of Extinction Rebellion unload a truck filled with horse excrements, in front of U.N. Climate Change Conference (COP25) in Madrid, Spain, December 14, 2019. REUTERS/Nacho Doce 

A Kenyan 'frogger' slum dweller Patrick Osunda dresses at the doorstep of his house before emptying excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 27, 2019. Picture taken February 27, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Patrick Osunda uses a broken plastic jerrycan to load excrement from a pit latrine into a metallic barrel in Kibera slum within Nairobi, Kenya February 24, 2019. Picture taken February 24, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Godffrey Ndalo uses a broken plastic jerrycan to empty excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 19, 2019. Picture taken February 19, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Godffrey Ndalo pulls a handcart loaded with excrement emptied from a pit latrine in Kibera slum within Nairobi, Kenya February 19, 2019. Picture taken February 19, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Godffrey Ndalo uses a broken plastic jerrycan to empty excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 24, 2019. Picture taken February 24, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Godffrey Ndalo uses a broken plastic jerrycan to empty excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 19, 2019. Picture taken February 19, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Godffrey Ndalo carries a broken plastic jerrycan which he uses to empty excrement from pit latrines in Kibera slum within Nairobi, Kenya February 24, 2019. Picture taken February 24, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Patrick Osunda dresses at the doorstep of his house before emptying excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 27, 2019. Picture taken February 27, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Patrick Osunda serves himself breakfast inside his house before emptying excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 27, 2019. Picture taken February 27, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Patrick Osunda washes his face outside his house before emptying excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 27, 2019. Picture taken February 27, 2019. REUTERS/Njeri Mwangi 

Kenyan 'froggers' slum dwellers Godfrey Ndalo and Patrick Osunda are assisted as they empty a metallic barrel of excrement from a pit latrine into a manhole in Kibera slum within Nairobi, Kenya February 24, 2019. Picture taken February 24, 2019. REUTERS/Njeri Mwangi 

Kenyan 'froggers' slum dwellers Godfrey Ndalo and Patrick Osunda empty a metallic barrel of excrement from a pit latrine into a stream bed that joins the Nairobi river in Kibera slum within Nairobi, Kenya March 3, 2019. Picture taken March 3, 2019. REUTERS/Njeri Mwangi 

A Kenyan 'frogger' slum dweller Patrick Osunda drinks tea inside his house before emptying excrement from a pit latrine in Kibera slum within Nairobi, Kenya February 27, 2019. Picture taken February 27, 2019. REUTERS/Njeri Mwangi 

A Correctional Services Department officer is seen next to a machine which inspects narcotics in the prisoner's excrement, at Pik Uk Prison, in Hong Kong, China February 14, 2019. REUTERS/Tyrone Siu 

Xing Hui, a 6-year-old giant panda born in China, is seen in his enclosure at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Hao Hao, a 6-year-old giant panda born in China, eats bamboo at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

A scientist collects a sample of panda excrements at the panda enclosure at Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

A scientist holds up a sample of panda excrements at the panda enclosure at Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Xing Hui, a 6-year-old giant panda born in China, defecates at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Xing Hui, a 6-year-old giant panda born in China, sits in his enclosure at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

A scientist collects a sample of panda excrements at the panda enclosure at Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

A scientist collects a sample of panda excrements at the panda enclosure at Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Xing Hui, a 6-year-old giant panda born in China, is seen in his enclosure at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Xing Hui, a 6-year-old giant panda born in China, sticks out his tongue at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Hao Hao, a 6-year-old giant panda born in China, eats bamboo at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Hao Hao, a 6-year-old giant panda born in China, eats bamboo at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Hao Hao, a 6-year-old giant panda born in China, eats bamboo at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Xing Hui, a 6-year-old giant panda born in China, eats bamboo at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

Xing Hui, a 6-year-old giant panda born in China, eats bamboo at the Pairi Daiza wildlife park in Brugelette, Belgium September 28, 2015. Belgian researchers are examining the excrements of giant pandas to understand how the bears can digest tough bamboo, hoping for clues on how to develop new generations of biofuel. REUTERS/Francois Lenoir

A Tenderloin Pit Stop portable toilet trailer is seen in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SOCIETY) 

A visitor enters a portable toilet facility held open by an attendant in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SOCIETY) 

An attendant (L) speaks with a visitor as he unlocks the door to a toilet in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SOCIETY) 

An attendant opens a door to a toilet for a visitor in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SOCIETY) 

Vehicles drive past a Tenderloin Pit Stop station in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SOCIETY) 

A used needle disposal receptacle is seen next to two portable toilets in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: DRUGS SOCIETY HEALTH) 

An attendant stands outside two portable toilets in the Tenderloin District in San Francisco, California December 30, 2014. Operated by the San Francisco Department of Public Works, the solar-powered toilets are part of a six-month pilot project aimed to provide clean and secure portable toilets, used needle disposal and dog waste stations throughout the Tenderloin District in an effort to alleviate the problem of human feces on the streets. REUTERS/Stephen Lam (UNITED STATES - Tags: HEALTH SOCIETY) 

A girl walks past a screen showing images of faeces flowing though the sewer system at an exhibition titled "Toilet !? Human Waste and Earth's Future" at the Miraikan National Museum of Emerging Science and Innovation in Tokyo July 3, 2014. The exhibition, which opened at the museum on Wednesday, explores the world of toilets, with the main exhibit centring around a massive toilet into which visitors are allowed to slide to simulate the journey of human waste matter into the sewers. The exhibit also includes five zones that range from showing exactly what one's excrement is made of to how different types of toilets are used around the world, and even a possible space toilet that could be used to grow plants. The exhibit is open until October 5 and costs 1,200 yen ($11.80) to visit. REUTERS/Issei Kato (JAPAN - Tags: SOCIETY HEALTH ENVIRONMENT) 

A woman walks past a choir of toilets that sing to thank visitors for putting in the effort of trying to learn more about what is normally a taboo topic of sitting on them, at an exhibition titled "Toilet !? Human Waste and Earth's Future" at the Miraikan National Museum of Emerging Science and Innovation in Tokyo July 3, 2014. The exhibition, which opened at the museum on Wednesday, explores the world of toilets, with the main exhibit centring around a massive toilet into which visitors are allowed to slide to simulate the journey of human waste matter into the sewers. The exhibit also includes five zones that range from showing exactly what one's excrement is made of to how different types of toilets are used around the world, and even a possible space toilet that could be used to grow plants. The exhibit is open until October 5 and costs 1,200 yen ($11.80) to visit. REUTERS/Issei Kato (JAPAN - Tags: SOCIETY HEALTH ENVIRONMENT TPX IMAGES OF THE DAY) 

A man wearing a faeces-shaped hat prepares to slide down into a five-metre (16.4-ft) toilet at an exhibition titled "Toilet !? Human Waste and Earth's Future" at the Miraikan National Museum of Emerging Science and Innovation in Tokyo July 3, 2014. The exhibition, which opened at the museum on Wednesday, explores the world of toilets, with the main exhibit centring around a massive toilet into which visitors are allowed to slide to simulate the journey of human waste matter into the sewers. The exhibit also includes five zones that range from showing exactly what one's excrement is made of to how different types of toilets are used around the world, and even a possible space toilet that could be used to grow plants. The exhibit is open until October 5 and costs 1,200 yen ($11.80) to visit. REUTERS/Issei Kato (JAPAN - Tags: SOCIETY HEALTH ENVIRONMENT) 

A girl wearing a faeces-shaped hat prepares to slide down into a five-metre (16.4-ft) toilet at an exhibition titled "Toilet !? Human Waste and Earth's Future" at the Miraikan National Museum of Emerging Science and Innovation in Tokyo July 3, 2014. The exhibition, which opened at the museum on Wednesday, explores the world of toilets, with the main exhibit centring around a massive toilet into which visitors are allowed to slide to simulate the journey of human waste matter into the sewers. The exhibit also includes five zones that range from showing exactly what one's excrement is made of to how different types of toilets are used around the world, and even a possible space toilet that could be used to grow plants. The exhibit is open until October 5 and costs 1,200 yen ($11.80) to visit. REUTERS/Issei Kato (JAPAN - Tags: SOCIETY HEALTH ENVIRONMENT TPX IMAGES OF THE DAY) 

The dog of a protestor carries a sign reading "the business of Deutsche Bank stinks more than my excrements" during a demonstration in the banking district of Frankfurt, November 12, 2011. Several thousand people build a cordon around the Frankfurt banking district on Saturday to protest against bankers, financiers and politicians they accuse of ruining global economies and condemning millions to poverty and hardship through greed. REUTERS/Kai Pfaffenbach (GERMANY - Tags: BUSINESS CIVIL UNREST) 

A worker throws bird dung to be processed on Ballestas island, south of Lima, October 9, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 9, 2011. REUTERS/Pilar Olivares (PERU - Tags: AGRICULTURE ANIMALS POLITICS ENVIRONMENT SOCIETY) 

A worker takes a rest from bird dung processing on Ballestas island, south of Lima, October 11, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 11, 2011. REUTERS/Pilar Olivares (PERU - Tags: AGRICULTURE ANIMALS POLITICS ENVIRONMENT SOCIETY) 

A worker takes a rest while processing bird dung on Ballestas island, south of Lima October 9, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 9, 2011. REUTERS/Pilar Olivares (PERU - Tags: AGRICULTURE ANIMALS POLITICS ENVIRONMENT SOCIETY) 

A worker walks among bags full of bird dung on Ballestas island, south of Lima, October 10, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 10, 2011. REUTERS/Pilar Olivares(PERU - Tags: AGRICULTURE ANIMALS POLITICS ENVIRONMENT SOCIETY) 

Workers collect bird dung on a field in Ballestas island, south of Lima, October 8, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 8, 2011. REUTERS/Pilar Olivares (PERU - Tags: AGRICULTURE ANIMALS POLITICS ENVIRONMENT SOCIETY) 

Workers run as they carry bags of bird dung on Ballestas island, south of Lima, October 9, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 9, 2011. REUTERS/Pilar Olivares (PERU - Tags: AGRICULTURE ANIMALS POLITICS ENVIRONMENT SOCIETY) 

A worker (C) walks in front of Guanay Cormorant birds on Ballestas island, south of Lima, October 9, 2011. Ballestas, like the other 21 islands along the Peruvian coast, is home to nearly 4 million migratory birds such as guanays, boobies and pelicans whose excrement make up the world's finest natural fertilizer. The bird dung, also known as guano, reached its greatest economic importance in the 19th century as a coveted resource being exported to the United States, England and France. With a current annual production of 20 thousand tons, Peru hopes to benefit mostly small farmers by boosting organic agriculture, the Rural Agrarian Productive Development Program (Agrorural) reported. Picture taken October 9, 2011. REUTERS/Pilar Olivares (PERU - Tags: POLITICS ENVIRONMENT ANIMALS SOCIETY AGRICULTURE)