Is feces biodegradable? (5 types of fecal color)

This topic shall answer the question of feces biodegradation.

It shall also cover other areas such as:

  • Definition of fecal matter.
  • The formation of feces.
  • The components of feces.
  • Applications of feces.
  • Environmental impact of feces.

Is feces biodegradable?

Yes, feces or fecal matter is biodegradable. The fecal matter is produced as a waste product of digestion. This waste matter is made up of organic residues like carbohydrates, proteins, lipids, and fiber. These are organic plant products that are susceptible to microbial degradation.

Feces is broken down by different microorganisms to produce small non-toxic molecules.

Biodegradation is the breakdown of organic matter by water, oxygen, light, radiation, bacteria, and fungi.

Biodegradation breaks down naturally occurring substances into small biomass and other products such as methane and carbon dioxide gases.

Some of the biomass becomes part of the soil, enriching the soil fertility, while some are assimilated by the bacteria and fungi to be used in their body systems.

Bacteria and fungi produce different products on biodegradation, depending on their enzymes or the chemical constituents of the substances being degraded.

Adhesives are also broken down into small matters depending on their chemical structure.

Another determinant for the products of biodegradation is the type of biodegradation that is taking place.

Aerobic biodegradation: this involves the breakdown of substances by bacteria or fungi in the presence of oxygen.

The gas produced in aerobic biodegradation is carbon dioxide.

Anaerobic biodegradation: this is the breakdown of substances in the absence of oxygen.

The bacteria or fungi use other gases like methane in place of oxygen.

The gas produced in this type of biodegradation is mainly methane which is used by the microorganisms for respiration.

Aerobic biodegradation occurs at a much faster rate than anaerobic respiration, on the other hand, anaerobic respiration is more efficient and thorough than aerobic respiration.

What is feces?

This is an animal’s solid or semi-solid waste of digestion that is excreted through the anus in a process called egestion or defecation.

Process of feces formation.

Feces is formed from the process of digestion. The following steps of digestion result in the formation of feces:

  • First, food is introduced into the mouth through a process called ingestion.
  • The food is then mechanically broken down into small particles by the use of teeth in a process called mastication.
  • Digestion of starch begins in the mouth where salivary amylase or ptyalin enzyme in the saliva breaks it down into maltose and dextrin.
  • Food is then turned into a bolus by the tongue and pushed down the stomach through the gut in a process called peristalsis.
  • Upon reaching the stomach, proteins are broken down by the enzymes pepsin and trypsin together with hydrochloric acid into small amino acid molecules.
  • The lipids are emulsified in the stomach by the bile salts, sodium glycocholate, and sodium taurocholate.
  • Water is absorbed in the stomach.
  • The pyloric sphincter muscle opens up and food is taken to the small intestines by the peristalsis.
  • Most of the digestion occurs in the small intestines.
  • Starch is broken down by pancreatic amylase and into maltose, and sucrose which are then acted upon by maltase and sucrase enzymes and converted into glucose.
  • Protein is broken down by trypsin and chymotrypsin into amino acids.
  • Lipids are broken down into fatty acids and glycerol by enzyme lipase.
  • At this point, the digestion process is complete, the products of digestion such as fatty acids, amino acids, and glucose are absorbed from the small intestines through the villi into the bloodstream.
  • Water is absorbed further from the large intestines or colon.
  • The indigestible material such as fiber, some proteins, some starch, some lipids, and unabsorbed water is then pushed into the rectum through the large intestines where they wait for excretion via the anus as feces.

Fecal matter produced has different names depending on the animals.

  • In humans, it is feces or poop in North America.
  • For cattle, it is called cow dung when in bulk, but cowpats or meadow muffins for individual cows.
  • For deer it is fewmets.
  • For wild carnivores it is scat.
  • For birds it is droppings.
  • For bats and seabirds, it is guano.
  • For herbivorous insects like beetles and caterpillars, it is frass.
  • For worms such as lugworms and earthworms, it is worm castings.
  • For horses, it is horse manure.
  • When animal feces are mixed with urine and other materials, they are called manure.

Properties of feces.

The following are the properties of fecal matter.

  • It has a unique smell due to thiols and skatoles, which are sulfur-containing compounds.
  • The appearance of feces depends on different diets and health but it is usually semisolid with a brownish color.

The brown color is due to digestion products of bile and bilirubin; a compound from dead red blood cells.

  • Fecal matter devoid of bilirubin will be free green.
  • Feces contain around 70% water and most of their solid texture is due to organic wastes.

What are the different colors of human feces?

Feces occur in different colors depending on the health or diet of an individual.

  • The brown color is the standard color of feces. It is formed by the bile and bilirubin products of digestion. Bile is obtained from the liver and bilirubin from the red blood cells.
  • The yellow color is caused by giardiasis infection that is caused by giardia bacteria. People with Gilbert’s syndrome also pass yellow feces. 

Yellow feces is also a sign of food passing very fast in the gut and therefore doesn’t contain bilirubin.

  • the pale or gray color is due to conditions such as cholecystitis, gallstones, hepatitis, pancreatitis, or cirrhosis that cause insufficient bile in the body.
  • Black or red color. Black is due to the presence of red blood cells in the feces, a condition called melena, caused by bleeding in the digestive tract, like in peptic ulcers, hemorrhoids, anal fissures, colon cancer, and ulcerative colitis.
  • The blue color is due to poisoning by radiation, thallium, and cesium.
  • The silver color is due to carcinoma of the ampulla of Vater.
  • The green color is due to a large amount of undigested bile in the digestive tract.

Applications of feces.

Feces have been put into different uses for some time now. The uses may vary from agricultural, and industrial to medical. Some of the applications of feces include:

  • Feces is used as a fertilizer.
  • Some useful bacteria can be extracted from feces and be transplanted to individuals with irritable bowel syndrome.
  • Feces are used in the production of biogas.
  • Feces, called paleofeces, are used in archeological research.
  • Animal dung is used as a cement to make mud-brick huts.
  • Some seeds are extracted from feces after their dormancy has been broken.
  • In Thailand, elephants are used to digest coffee beans to make black ivory coffee. These seeds are obtained from elephant dung.
  • Dog feces was once used in leather tanning.
  • Cow dung and urine are used in India to make the Hindu drink, panchagavya.
  • In some countries, cow dung is consumed to treat illnesses such as dysentery.

Is feces eco-friendly?

According to a journal on the eco-friendliness of human feces, the waste is biodegradable and therefore eco-friendly.

Feces contain waste products of digestion. The majority of components found in feces are water and organic compounds such as sugars, cellulose fibers, some amino acids, and some lipids.

These materials are broken down into simpler biomass that is not environmentally toxic.

Feces can be used in making biogas and fertilizer and therefore do not accumulate in the environment.

The handling of feces should be done carefully though, if improperly disposed of, feces contain some bacteria and worms such as Ascaris lumbricoides which may enter the body and cause diseases such as ascariasis.

Feces also contain sulfur-based molecules with a foul smell that pollutes the air. 


This article has covered the biodegradability of fecal matter and its physical properties and uses.

It has also covered other areas such as:

  • The digestion process.
  • Applications of feces.
  • Different names for feces.
  • Eco-friendliness of feces.

For any questions or comments please use the comment section below.

Frequently Asked Questions (FAQs): is feces biodegradable?

Is human feces good for plants?

Yes, feces is rich in nutrients such as nitrogen, sulfur, and carbon which are essential nutrients of the plant.

Fecal matter has long been used as fertilizer because of its high amounts of essential elements.

What happens to poop in nature?

Poop, an informal name for feces, is broken down by bacteria and fungi to form simple particles that are non-toxic to the environment. 

Can you compost human poop?

Yes, human poop can be broken down by microorganisms in compost to release essential elements necessary for healthy crops. So feces can be composted to make that very nutrient-rich manure.


Ping Zhu, Xusheng Pan, Yilin Shen, Xiang Huang, Fang Yu, Deli Wu( June 2022). Biodegradation and the potential effect of ranitidine during aerobic composting of human feces.

Retrieved from:!

Miguel Angel Lopez Zavala et al.,( March 2004). Modeling of aerobic biodegradation of feces using sawdust as a matrix.

Retrieved from:

Yokoyama, M. T.; Carlson, J. R. (1979). “Microbial metabolites of tryptophan in the intestinal tract with special reference to skatole”. The American Journal of Clinical Nutrition. 32 (1): 173–178. doi:10.1093/ajcn/32.1.173

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