Swamp gas or marsh gas has been known by many names throughout the ages. The fascination was not with the gas but with the lights they produced. Travellers, campers and hunters generated innumerable stories over the eerie burning light often seen over swamps. English folklore has them mentioned as ‘ will-o’-the-wisp’. In USA they are called ‘ghost lights’. There have been countless myths associated with this phenomenon. Science has given the answers to the occurrence of these mysterious lights. But even in present day people get spooked on sighting these over swamps or marshlands.
What are Swamps?
Swamps are wetlands inhibited by woody trees and shrubs. Wetlands are defined as areas of land whose soil is saturated with water either permanently or seasonally. Swamps have their unique ecosystems and contain lots of thriving plants and animals.
What is Swamp Gas?
Swamp gas is the gaseous decomposition product originating from decaying organic matter in the absence of air. In order to understand why and how swamp gas is formed we need to understand the process of degradation or breakdown of dead plants and animals.
Aerobic decomposition
People see death and decay of plants and animals all around them. These are all made up of organic matter i.e. mainly made up of carbon, hydrogen and oxygen. When the decomposition occurs in the presence of air which has oxygen, the bi-products are carbon-di –oxide (CO2), water (H2O) and energy in form of heat.
It is exactly how food people consume is broken down in the body. The gastric juices, enzymes and friendly germs in our gut break down the carbohydrates proteins and fats into smaller units called glucose, amino acids and fatty acids. Our body either uses these molecules to form new units or degrade them in simple waste products thereby releasing energy. This process is called metabolism.
You can also observe the degradation process in household composting or garden composting. The compost heap is turned every few days to aerate it. A compost heap gets get hot during the degradation process. Temperatures can reach to 60 degree centigrade. The degraded simple waste products in this case are water, carbon dioxide and energy or heat.
However the above mentioned processes occur mostly in the presence of air. These are aerobic processes. In the absence of air, the end products are different which why swamp gas is formed.
Anaerobic decomposition
Within any ecosystem death plays an important part. However dead and decaying plants and animals in the swamps slowly get buried in the supersaturated soil. There they keep degrading in absence of air. The anaerobic bacteria, present in abundance in swamps, breakdown the dead plants and animals. The gases formed as a result are Methane(CH4), carbon di oxide(CO2) , nitrogen(N) and traces of Hydrogen(H),carbon mono oxide(CO), propane(C3H8), hydrogen sulphide (H2S), phosphines(PH3) other hydrocarbons.
Famous scientist Alessandro Volta (1745-1847) isolated methane from swamp gas in 1783, prior to his work on electricity. Possible explanation of self ignition of the ‘swamp gas’ given by science is that the combination of methane with self igniting phosphines or diphosphines (P2H4) which also emit from the swamps, result in the light eerie blue flames.
Methane is a greenhouse gas and a major contributor of global warming. Besides swamps, landfills, bogs, rice fields, animals like cows produce methane.This gets accumulated in the atmosphere and traps the heat emitting from the earth, resulting in raising temperatures of the Planet.
