Propane buses aren’t clean. We need electric buses instead.

Switching from one dirty fuel source to another isn’t the public health or climate progress we need.  

Mac Dressman

America’s accelerating transition to clean energy and electric vehicles presents an existential threat to the fossil fuel industry. With its back against the wall, the industry has been forced to get creative about rebranding dirty fossil fuels as “clean, green” solutions. In particular, industry lobbyists have started to push propane, a byproduct of methane or “natural” gas production, as a clean and environmentally-friendly alternative to replace diesel buses

But propane buses are not a clean, safe alternative to diesel. First off, propane and methane gas emit climate-warming greenhouse gasses. Instead of switching from one climate change-causing fuel source to another, we should be focused on zero-emission vehicle technology that can run on renewable energy. There is no reason to dig ourselves a deeper hole of fossil fuel-dependency. 

Transportation is the nation’s number one source of climate-harming emissions, contributing to worsening droughts, hurricanes and wildfires. Moreover, every year, air pollution from cars, trucks and other vehicles cuts short an estimated 58,000 lives. To address these environmental and public health crises, we need to move away from fossil fuel pollution and embrace clean transportation solutions instead.   

While diesel is one of the dirtiest transportation fuels, propane buses are still dangerous to public health. Thomas Built Buses, which produces diesel, propane and electric buses, has found that although propane buses emit less nitrogen oxide pollution than diesel, propane buses still emit air pollutants like carbon monoxide and non-methane hydrocarbons.

Carbon monoxide is lethal at high doses in enclosed spaces. Even as outdoor pollution, it can be harmful to those with some types of heart disease. Non-methane hydrocarbons are also dangerous, as they contribute to ground-level ozone. Exposure to ground-level ozone is particularly harmful to children and the elderly, often causing chest pain, coughing, throat irritation and airway inflammation. It can also aggravate lung diseases such as asthma, emphysema, and chronic bronchitis. 

Unfortunately, propane buses still emit these air pollutants, sometimes at even higher levels than diesel buses.

To prove the benefits of propane, proponents generally point to one study that compared emissions from diesel buses and propane buses. The study concludes that propane gas buses emit less harmful nitrogen oxide pollution. However, during city and interstate driving, propane buses actually emitted more carbon dioxide than the diesel buses. Furthermore, propane buses emitted higher levels of carbon monoxide (CO) and total hydrocarbons. 

The picture is clear: Propane buses still emit toxic fumes that endanger public health and threaten the climate. 

In comparison, zero-tailpipe-emission electric buses do not release direct emissions or harmful fumes that pollute our communities. Even though we still rely on fossil fuels to produce electricity in many places, electric buses still emit less CO2 emissions compared to fossil-fuel powered buses. And as the share of renewable energy used across the country continues to rise, electric buses will get even cleaner. 

The bipartisan Infrastructure Investment & Jobs Act, passed in November, will deliver $2.5 billion in funding specifically for zero-emission electric school buses. It also included an additional $2.5 billion for all types of “low-emission” school buses, which could fund electric, propane or methane gas buses. For maximum environmental and public health benefits, the majority of this “low-emission” funding should go to clean electric buses instead of to buses that rely on fossil fuels.  

In the face of massive environmental and public health crises, America has a choice. We can rebrand dirty fossil-fuel powered vehicles as “clean” and continue to pollute our air and harm the climate, or we can seize this opportunity for healthier air and a safer planet by truly transforming transportation for the better.


Image credit: Stuart Cunningham,


Mac Dressman