CNG CNG Environmental and Economic Benefits 2 — Questions and Answers
Question 1: CNG produces lower levels of which air pollutant, making it preferred in urban areas with smog concerns?
- Nitrogen oxides (NOx) (Correct answer)
- Sulfur hexafluoride (SF6)
- Chlorofluorocarbons (CFCs)
- Ozone (O3)
Correct answer: Nitrogen oxides (NOx)
CNG produces significantly lower NOx emissions compared to diesel, reducing smog formation in urban environments.
Question 2: What is the primary domestic source of natural gas used for CNG fuel in the United States?
- Shale gas extraction (hydraulic fracturing) (Correct answer)
- Coal gasification
- Imported liquefied natural gas (LNG)
- Biomass fermentation only
Correct answer: Shale gas extraction (hydraulic fracturing)
The majority of U.S. natural gas, including that used for CNG, comes from domestic shale gas extraction through hydraulic fracturing.
Question 3: Renewable Natural Gas (RNG) used as CNG fuel is typically sourced from which waste stream?
- Landfill biogas and wastewater treatment plants (Correct answer)
- Coal mines
- Nuclear power plant cooling systems
- Industrial chemical plants
Correct answer: Landfill biogas and wastewater treatment plants
RNG is produced by capturing and processing methane from landfills and wastewater treatment facilities, making CNG carbon-neutral or carbon-negative.
Question 4: Which CNG emission benefit makes it particularly attractive for fleet operators subject to EPA's National Ambient Air Quality Standards (NAAQS) compliance zones?
- Near-zero particulate matter and lower NOx emissions (Correct answer)
- Zero carbon dioxide output
- No need for emission testing
- Higher octane rating than diesel
Correct answer: Near-zero particulate matter and lower NOx emissions
CNG's near-zero PM and lower NOx help fleet operators comply with NAAQS in nonattainment areas where air quality standards must be met.
Question 5: For a transit agency evaluating a switch from diesel to CNG buses, which total cost of ownership (TCO) factor most commonly offsets higher vehicle purchase prices?
- Lower fuel cost per mile over the vehicle's lifetime (Correct answer)
- Reduced driver training requirements
- Lower insurance premiums
- Shorter maintenance intervals
Correct answer: Lower fuel cost per mile over the vehicle's lifetime
Lower CNG fuel costs per mile, accumulated over hundreds of thousands of miles, typically offset the higher initial purchase price of CNG buses.
Question 6: Which carbon accounting standard allows fleet operators to claim carbon-negative status when using RNG-sourced CNG?
- EPA's Renewable Fuel Standard (RFS) pathway credits (Correct answer)
- ISO 14001 environmental management
- OSHA Hazard Communication Standard
- DOT Hazardous Materials Regulations
Correct answer: EPA's Renewable Fuel Standard (RFS) pathway credits
EPA's Renewable Fuel Standard assigns RNG pathways (e.g., landfill gas) with carbon intensity scores that can be carbon-negative, qualifying for D3 or D5 RINs.
CNG CNG Environmental and Economic Benefits 2
CNG produces lower levels of which air pollutant, making it preferred in urban areas with smog concerns?