Are CNG Buses An Environmentally Friendly Option?
Combating climate change requires innovation in various sectors, and public transportation is no exception. For example, compressed natural gas buses—or CNG buses—use emerging technologies that could revolutionize public transit’s carbon footprint.
As the US government introduces many climate-positive transportation measures, CNG buses could be the key to reaching new emissions reduction benchmarks and decreasing reliance on nonrenewable fossil fuels.
But what is a CNG bus? Are CNG buses any more environmentally friendly than their diesel counterparts? Throughout this guide, we’ll explore CNG and discuss four key advantages of implementing CNG in bus fleets nationwide.
What is Compressed Natural Gas (CNG)?
The US currently uses two forms of natural gas—liquefied natural gas (LNG) and compressed natural gas (CNG).
Fuel manufacturers create CNG by substantially compressing natural gas. As a result, CNG takes up less than 1% of the volume it did in its original form. But why compress natural gas in the first place?
- Harnessing Boyle’s Law – Compressibility is a property of all gasses, including natural gas. It was first observed by chemist Robert Boyle in the 1660s, who reported that the volume of a gas is inversely proportional to the pressure applied to it at a constant temperature. Compressing a gas optimizes its storage and transport without changing its chemical properties.
- Size matters – Using natural gas in its extracted form for vehicle fueling wouldn’t be feasible. To mirror fuel combustion performance, vehicles must have access to a significantly higher volume of natural gas than traditional fuel. But, since compressing the gas doesn’t change its chemical composition, pressurizing it can solve the volume problem for natural gas-powered vehicles and machinery.
Advantages of Using CNG for Public Transit
We’ve mentioned that CNG can be used to power internal combustion engines—thus, they can be used in public transit applications. Let’s explore four significant benefits of incorporating CNG buses into transportation infrastructure.
Internal combustion relies upon a basic chemical reaction:
- Fuel + Oxygen (O2) → Carbon dioxide (CO2) + Water (H2O)
There are always two byproducts of combustion: carbon dioxide and water. However, diesel combustion produces more carbon dioxide emissions than CNG.
In diesel combustion, forty-eight parts of carbon dioxide are released for every four parts of fuel burned. But, only four parts of carbon dioxide are emitted for every four parts of CNG combusted—a significantly lower emissions profile than diesel combustion.
So, CNG vehicles are much less expensive to operate than their diesel counterparts.
But it’s important to note that CNG buses come at a higher upfront cost. The average CNG bus is between $25,000 and $50,000 more expensive to build than diesel buses. But with over $1.00 per gallon saved on fuel, CNG buses rapidly pay for themselves as the fuel savings grow to offset the increased purchase price.
Many suburban areas regulate noise pollution, enforcing noise ordinances that can impede the expansion of public transit. Simply put, buses can be distractingly loud.
However, CNG engines are up to ten decibels quieter than comparable diesel engines. While reduced engine noise may not sound like a significant concern, studies have shown that noise pollution can cause numerous health detriments, including:
- Noise-Induced Hearing Loss (NIHL)
- Sleep disruption
- High blood pressure
- Speech interference
In addition, the US Environmental Protection Agency (EPA) sets limits on noise sources, including construction equipment, transport vehicles, trains, and more. Municipalities can bolster their compliance efforts by implementing CNG buses, improving the quality of life for riders and residents.
All in all, CNG performs better than diesel fuel in a combustion context. Let’s explore three critical performance metrics:
- Particulate matter emissions: While diesel engines emit visible and detectable particulate matter (PM) in black soot, CNG engines emit nearly zero PM. According to the US Department of Energy, a study on a Colorado bus system demonstrated that CNG buses emitted 97% less PM than diesel buses, including a 57% drop in nitrous oxide emissions.
- Collision safety: CNG fuel tanks are much stronger and safer than diesel tanks. Since CNG is stored (even in vehicles) at high pressures, fuel tanks are robustly designed, preventing explosions in the event of CNG-powered bus crashes.
- Vapor safety: CNG vapors are odorless, colorless, and non-toxic—however, diesel and gasoline vapors are dangerous to ingest and breathe. While vapor buildup in enclosed spaces can lead to asphyxiation, fuel inhalation during fueling is a significantly lower concern for CNG vehicles.
Choose FASTECH for Your Renewable Energy Fueling Projects
CNG buses are an environmentally friendly option, outperforming diesel and gasoline engines in emissions profiles, price, and safety.
As alternative fuel becomes more mainstream, is your business prepared to embrace a fossil-fuel-free world? If you’re ready to champion a clean energy future, turn to the experts at FASTECH. We engineer and build end-to-end renewable energy solutions, helping green companies crush their emissions goals.
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