What fuels release the most CO and CO2 emissions, most to least?

What fuels release the most CO and CO2 emissions, most to least?

• A. Petrol (Type 1), Diesel (Type 2), Electric-Petrol (Type 8)
• B. Diesel (Type 2), Petrol (Type 1), Electric-Petrol (Type 8)
• C. Electric-Petrol (Type 8), Petrol (Type 1), Diesel (Type 2)
• D. Petrol (Type 1), Electric-Petrol (Type 8), Diesel (Type 2)

Answer: (A)

The key idea is that emissions depend on both how much carbon is in the fuel and how efficiently that fuel is burned in the engine. Petrol engines tend to release more carbon monoxide and carbon dioxide per kilometer than diesel engines, partly because petrol combustion can produce more CO and because petrol’s energy is burned in engines that are less efficient for CO2 output per distance. Diesel engines are more thermally efficient and generally emit less CO2 per kilometer, even if they can produce more NOx or particulates in other respects. A petrol–electric hybrid uses electric power for part of its movement, which means less fuel is burned at the tailpipe and overall emissions are reduced further. So, ranking from highest to lowest CO and CO2 emissions is petrol first, then diesel, and electric-petrol last.

The key idea is that emissions depend on both how much carbon is in the fuel and how efficiently that fuel is burned in the engine. Petrol engines tend to release more carbon monoxide and carbon dioxide per kilometer than diesel engines, partly because petrol combustion can produce more CO and because petrol’s energy is burned in engines that are less efficient for CO2 output per distance. Diesel engines are more thermally efficient and generally emit less CO2 per kilometer, even if they can produce more NOx or particulates in other respects. A petrol–electric hybrid uses electric power for part of its movement, which means less fuel is burned at the tailpipe and overall emissions are reduced further. So, ranking from highest to lowest CO and CO2 emissions is petrol first, then diesel, and electric-petrol last.