Cars have catalytic converters to stop pollutants from escaping into the air. These devices monitor exhaust oxygen levels so the engine control unit can adjust the air-to-fuel mix. The goal is hitting the stoichiometric point. That’s the ideal ratio. It ensures just enough oxygen exists to burn off carbon monoxide and other bad stuff in the exhaust stream.
The catch is heat. Catalytic converters only work when hot. Cold starts are a problem. Pollution isn’t reduced effectively right when you turn the key.
You could preheat the converter with an electric resistance heater. But most car electrical systems can’t do it fast enough. People don’t want to wait minutes before driving. Hybrid batteries have the power to heat the unit quickly. Standard 12-volt systems? Not so much.
Diesel engines run cooler than gasoline ones. Their converters struggle with nitrogen oxides. NOx causes acid rain and smog. The solution is a urea solution. Also called carbamide. It contains carbon, hydrogen, nitrogen, and oxygen.
Injecting urea into the exhaust pipe causes it to evaporate. It mixes with the exhaust gas. A chemical reaction occurs. The urea breaks down NOx. It produces water vapor and nitrogen. Over 90 percent of nitrogen oxides are disposed of this way. Urea comes from the urine of amphibians and mammals.
