Since steam is mostly water vapor, many people would assume that steam engines are not bad for the environment.
However, steam trains usually burn fossil fuels like coal as part of the process of creating steam, so they are not as green as you might initially think.
Here’s everything you need to know about the environmental impact of steam trains.
1. Do Steam Trains Cause Pollution?
Since steam is essentially water vapor, you might not think steam trains would cause pollution.
Unfortunately, this is not the case.
So, burning these materials does cause pollution. Mining and drilling for coal and gas can cause pollution too.
Coal releases more carbon dioxide per unit of energy than other fossil fuels, which is particularly concerning.
Methane is one of the most worrying unburned hydrocarbons because it is more potent at trapping heat than carbon dioxide.
Meanwhile, when sulfur dioxide comes into contact with other substances in the atmosphere, it can result in acid rain.
Although burning natural gas does not seem to release as much pollution as coal, it’s still not exactly green.
The biggest concern is the pollution associated with drilling for gas, so steam trains furthering the demand for gas are still unsustainable.
Combusting gas still releases ammonia (NH3), NOX, and particulate matter (PM).
While you might think burning wood is better since wood is renewable, there are still some environmental concerns.
Trees sequester CO2 throughout their lifetime, but this is released when they are burned.
Burning wood can also release PM, which can be harmful to humans or animals who breathe it in.
There has been research into using biocoal for steam engines, which is greener as it eliminates the need for mining.
This is made when biomass is heated until it becomes a solid material.
Biocoal also does not appear to be as polluting as regular coal.
2. Is Steam Harmful to the Environment?
Since steam is water in another form, you might think it’s harmless.
However, water vapor is actually considered a greenhouse gas and is the most abundant greenhouse gas in the atmosphere.
So, steam contributes greatly to the greenhouse effect.
With that said, it’s not clear if the steam from steam trains would contribute much or at all to this.
3. Are Steam Trains More Eco-Friendly than Diesel Trains?
Steam trains do not seem to be greener than diesel trains.
Diesel is a fossil fuel, while steam trains typically rely on fossil fuels too, so neither of them is sustainable in that regard.
Trains powered by diesel can release pollutants like particulate matter (PM), carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NOx).
However, burning coal or natural gas can also release these kinds of emissions.
What’s even more concerning is that diesel trains release emissions even when idle.
Steam trains also continue to release emissions when idle as the fire is not extinguished while the journey is still ongoing.
For example, an idle diesel train can release an average of 43 mg/m3 when idling but around 239 mg/m3 at the highest speed – which is referred to as notch 8.
The same idle diesel train can release an average of 147 ppm (parts per million) of thermal NOx, but at the highest speed, this increases to around 1137 ppm.
Thermal NOx refers to nitrogen oxides that are created when nitrogen in combusted hot air is oxidized.
As for CO, a diesel train can release 389 ppm at the highest speed and 94 ppm in an idle state.
Furthermore, this same idle diesel train can release an average of 4.3 ppm of HCs and 7.6 ppm at the highest speed, or notch 8.
As mentioned earlier, burning fuel matter for steam trains can also release pollutants, but it is not clear exactly how much of these compounds are released.
In the US alone, diesel-electric trains can release 35 million tonnes (35 megatonnes) of CO2 annually.
Meanwhile, research in China found that from 1975 to 1988, steam trains were behind 35 Mt (megatonnes) of CO2 per year, but the figure has fallen drastically as these trains became less popular.
4. Are Steam Trains More Eco-Friendly than Electric Trains?
Steam trains are not more eco-friendly than electric trains, quite the opposite is true.
Diesel trains emit more than 90g of CO2 per passenger for every kilometer traveled, while an electric train releases 45g per passenger.
As mentioned earlier, steam trains release similar levels of CO2 as diesel-electric trains (which are not the same as standard electric or diesel trains as the train can alternate between these two fuel sources).
Most electricity is not sustainable because it’s mostly powered by fossil fuels, so both of these trains are relying on unsustainable sources of fuel.
Although electric trains do not release tailpipe emissions, that doesn’t necessarily mean they’re emission-free.
There are still emissions released from generating the electricity in the first place, as well as from building and maintaining these trains and the train tracks.
With that said, steam trains are also not energy-efficient, but electric trains are.
While electric trains are not fully sustainable, they are a greener option since they do not release tail-pipe emissions.
There are also solar-powered electric trains which are even greener as they don’t rely on fossil fuels, however, these are not common.
5. Do steam trains still exist?
Although steam trains still exist, they are very rare these days.
Most modern trains are powered by diesel or electricity, which became the more prominent models throughout the 1940s and the 1960s, so the remaining steam engines are typically tourist attractions.