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 detailed view of camel feces at the animal waste transfer station in Adhen Village, Ras al Khaimah, United Arab Emirates July 16, 2019. Picture taken July 16, 2019. REUTERS/Christopher Pike

A camel defecates at a farm in Adhen Village, Ras al Khaimah, United Arab Emirates July 16, 2019. Picture taken July 16, 2019. REUTERS/Christopher Pike

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

A woman puts feces in a bucket to prepare "Poopootovs", which is a play on Molotov cocktails, before they are thrown at security forces during protests, in addition to the usual rocks and petrol bombs, in Caracas, Venezuela May 9, 2017. REUTERS/Christian Veron TPX IMAGES OF THE DAY

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 cow is silhouetted in front of manure at the farm owned by French farmer Franck Pellerin (not pictured) in La Chapelle-Caro, central Brittany, France, September 2, 2015. REUTERS/Stephane Mahe

A girl stands beside the gate of her family home with cow dung cakes on wall, on the outskirts of Peshawar January 22, 2015. REUTERS Fayaz Aziz (PAKISTAN - Tags: SOCIETY)

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)

A woman pastes cow dung cakes on a wall for drying in the northern Indian city of Allahabad April, 16, 2014. REUTERS/Jitendra Prakash (INDIA - Tags: SOCIETY TPX IMAGES OF THE DAY) FOR BEST QUALITY IMAGE ALSO SEE: GM1EAB40N8U01

Sadhus, or Hindu holy men, perform prayers while sitting inside circles of burning "Upale" (or dried cow dung cakes) on the banks of the river Ganges during the Magh Mela festival in the northern Indian city of Allahabad February 4, 2014. REUTERS/Jitendra Prakash (INDIA - Tags: RELIGION SOCIETY TPX IMAGES OF THE DAY)

Butterflies congregate on dog faeces set by butterfly hunters in Bangui, Central African Republic, December 1, 2013. Mosaics made out of butterfly wings are a popular art form in Central African Republic. Professional butterfly hunters gather butterflies in the forest outside Bangui, then sell them to artists, who use the wings to make mosaics. The hunters use palm wine, urine and dog feces as traps to attract the butterflies. Picture taken December 1, 2013. REUTERS/Joe Penney (CENTRAL AFRICAN REPUBLIC - Tags: ANIMALS SOCIETY ENVIRONMENT BUSINESS)

Marinela Bucurestean (L) watches as her grandson Amador (C) poops in his diaper, while combing the hair of her niece's daughter Rebeca and babysitting her other grandson Iani (R) at her home in the shanty town settlement of El Gallinero, in the outskirts of Madrid November 23, 2013. Several hundred Romanian gypsies live in precarious conditions, without running water or sewage services, in El Gallinero, just 15 km (9 miles) away from Madrid's centre. The inhabitants live in ramshackle huts made out of cardboard and zinc in an area prone to flooding. REUTERS/Susana Vera (SPAIN - Tags: SOCIETY POVERTY)