“Electrification” is good for your air

When you live in a city and use public transportation, there are certain conveniences, like not having to put gas in your car for the commute, or new tires for all the miles, or paying for parking space at either end.  However, you’re at the mercy of some negative things that come with public transport: the schedule doesn’t always suit your schedule and can be delayed or changed,  there are lots of people and microbes to contend with, and the transport method can generate a lot of air pollution.  

Speaking to this last “con”, you may not realize it, but much of the grime of bus and railway stations comes from the air pollutants that settle out of the air onto surfaces.  Where trains or buses are diesel-powered, a (sometimes visible) smog covers the station, routes and neighborhoods surrounding them.  Diesel was the fuel of choice for decades because of its power.  Here’s why:  Diesel fuel is denser than gasoline and contains about 15% more energy by volume. Accounting for the difference in energy density, the overall efficiency of the diesel engine is approximately 20% greater than the gasoline engine, despite the diesel engine also being heavier.  (Differences between diesel and petrol explained)  This is why vehicles with heavy loads like buses, trains and semi-trucks are traditionally diesel-powered. 

However, city leaders are slowly understanding the toll that diesel fumes have on their cities.  When I visited London in 1999-2000, I spent a lot of time walking and took a few bus tours.  I didn’t notice any air pollution during the day, but I couldn’t believe what I saw when I blew my nose at night: the tissue turned black!  There was obviously a lot of soot in the air that I was taking in with every breath–and I was just a tourist.  What about the people who work, live and commute in this city every day of the year?  The soot is PM2.5 particulates, which contain unburned or partially burned hydrocarbons.  Newer diesel engines can be fitted with particulate filters, but these tend to clog up when used mainly for urban driving, and diesel produces more nitrogen dioxide than gasoline, making it one of the main sources of this toxic gas. (Fact Check: are diesel cars really more polluting than petrol cars?)

Diesel exhaust has bad effects on people as well the city infrastructure.  According to the EPA, exposure to diesel exhaust can lead to serious health conditions like asthma and respiratory illnesses and can worsen existing heart and lung disease, especially in children and the elderly. These conditions can result in increased numbers of emergency room visits, hospital admissions, absences from work and school, and premature deaths. Diesel emissions also contribute to the production of ground-level ozone which damages crops, trees and other vegetation. Acid rain is also produced, which affects soil, lakes and streams…and even buildings (stone and cement) in the city.  Question: would you eat from any vegetable garden in a city? 

Europe still has more diesel cars and trucks on the road than gasoline ones,  because of higher MPG and fantastic highway efficiency.  (Why Diesel Cars Are King in Europe but Nearly Extinct in the United States)  Thankfully, London is slowly transitioning to a clean bus fleet.  London has the largest zero-emission bus fleet in western Europe. Around 2,500 zero-emission buses operate across London, 28% of the entire fleet. This means more than a quarter of buses in London are using zero-emission technology.  The zero-emission fleet is made up of hydrogen, battery electric and opportunity charged buses which are topped up using a pantograph multiple times a day. (Improving Buses)  The goal is to have the entire fleet zero emission by 2034.  I’m pretty sure that visiting London today would be an entirely different experience.  

San Francisco is also experiencing a clean air “renaissance” right now. Switching from diesel to electric trains dramatically improved the air quality aboard the San Francisco Bay Area's Caltrain commuter rail line, reducing riders' exposure to the carcinogen black carbon by an average of 89%. (Study finds dramatic boost in air quality from electrifying railways)  The researchers who wrote the study happened to start measuring the pollution at the right time.  For four weeks, they tracked the rapid improvements in air quality as old diesel locomotives were replaced by new electric trains.

What does this cut in exposure to black carbon mean?  For commuters, it cuts the cancer death risk by 51 per 1 million people, and 330 per 1 million people for train conductors.   All together, it eliminates hundreds of cancer deaths per year for the area. 

Where else could this be applied?  Plenty of places.  

• When a coal-processing plant in Pennsylvania shut down in 2016 after 54 years of operation, the area experienced an immediate 42% drop in cardiovascular emergency department visits in the surrounding community compared with the preclosure average number of heart-related visits.  What a relief on the bodies of those who were exposed to these particulates and toxins 24/7 for most of their lives!  (How 70,000 people stopped “smoking” overnight)  A Detroit incinerator shut down in 2019 and although the health changes would also be interesting to analyze, these have not been disclosed.  Pre-shutdown, the children in the area were hospitalized at a rate of three times higher than the state average as a direct result of the incinerator.  (Incineration is not the best "answer" to our waste issues)  Our energy and waste disposal industries still poison residents and workers in other areas.  

• About 30% of New York City’s buses are hybrid (usually diesel-electric), compressed natural gas (CNG) or battery-driven. (Low-emission buses in New York City)  In 2022, an academic study showed that the MTA's increased use of CNG and hybrid-electric buses between 2009 and 2014 led to improvements in air pollution across the city.  

• Amtrak, the national passenger railroad company of the US, operates a fleet of 2,142 railway cars and 425 locomotives for revenue service and railroad operations. (List of Amtrak rolling stock)  At least 73% of the locomotives are diesel, some are electric and some are dual-mode (diesel electric).  In remote areas, running under combustion power seems to be cheaper than investing in long-distance electric rails.  However, the dual-mode is a good compromise because the diesel engines are used as generators to charge batteries, which then power the locomotive to move.  Using the diesel engine in this way as an “always on” generator is more fuel efficient and produces less pollutants. 

Photo by Stefano Lombardo on Unsplash