Town gas, a manufactured gaseous fuel, served as a major public utility for households and industries across the world, particularly during the 19th and early 20th centuries. Before the widespread adoption of natural gas, this manufactured gas was the primary source for municipal public and domestic supply. Its introduction marked a significant step in urban infrastructure, providing a clean, controllable energy source compared to burning raw coal in homes.
Composition and Production Methods
Town gas was not a single, standardized substance but a mixture of gases whose composition varied based on the raw materials and manufacturing process used. The primary combustible components were hydrogen and carbon monoxide, along with smaller amounts of methane and other volatile hydrocarbons. The high hydrogen content, often ranging from 30% to over 50% of the total volume, gave the fuel a relatively high burning velocity.
The initial and most common production method involved the carbonization of bituminous coal, known as “destructive distillation,” which yielded “coal gas.” Coal was heated in the absence of air, releasing volatile matter as gas and leaving behind coke as a solid by-product. This raw gas was highly impure, containing toxic hydrogen sulfide and ammonia, necessitating an extensive purification process before distribution.
Another important manufacturing technique was the water gas process, which involved blowing steam over incandescent coke or coal. This reaction produced a gas mixture rich in carbon monoxide and hydrogen. Later, especially in the 1960s, processes were developed to manufacture town gas from liquid feedstocks like heavy oil and naphtha through steam reforming, offering a cleaner and more efficient gas.
Primary Domestic and Industrial Uses
The earliest and most prominent use of town gas was for public and commercial illumination, giving rise to the iconic gaslight era. Gas lamps became common fixtures on city streets, offering a much brighter and more stable light than oil lamps or candles. The invention of the gas mantle in the late 1800s significantly enhanced this utility, producing a brighter, more efficient light when heated by the gas flame.
Town gas utility expanded into domestic heating and cooking, replacing raw coal in many urban areas. Gas stoves and ovens offered a controllable and quick-to-use alternative to cumbersome coal stoves, providing major convenience for households. Furthermore, town gas was used in early industrial processes requiring a stable and concentrated heat source.
Key Safety and Health Concerns
The most significant difference between historical town gas and modern natural gas is the presence of high concentrations of carbon monoxide (CO), which presented a serious public health hazard. Town gas, particularly that produced from coal or water gas processes, contained substantial amounts of this colorless and odorless gas. CO is highly toxic because it binds to the hemoglobin in the blood, effectively displacing oxygen and depriving the body’s organs of the necessary supply.
Accidental exposure to carbon monoxide from a leaky pipe or an unlit appliance burner was a frequent cause of accidental poisoning. Even low concentrations could lead to symptoms like headache and fatigue, while prolonged exposure could cause unconsciousness, brain damage, and death. In contrast, the natural gas used today is primarily methane, which is non-toxic, although it still poses risks related to explosion and suffocation.
The Transition to Natural Gas
The widespread use of town gas began to decline with the discovery of large, accessible reserves of natural gas, primarily composed of methane, starting in the mid-20th century. This transition was driven by compelling economic and safety factors, as natural gas was cheaper to produce and transport over long distances. A major advantage of the new fuel was its non-toxic nature, as it lacked the dangerous carbon monoxide content of town gas, thereby eliminating the risk of CO poisoning from leaks.
The switch required a massive, coordinated infrastructure project because natural gas has a higher calorific value and different burning properties than town gas. For instance, in the United Kingdom, a nationwide conversion project began in the late 1960s, requiring access to every home and business on the network. Over the course of about a decade, approximately 40 million domestic appliances were either converted or replaced entirely to handle the new fuel’s chemical properties. This effort involved building a national transmission system and ultimately led to the complete replacement of the old manufactured gas system with the modern natural gas network.