Diesel exhaust

Diesel exhaust is the gaseous exhaust produced by a diesel type of internal combustion engine, plus any contained particulates. Its composition may vary with the fuel type or rate of consumption, or speed of engine operation (e.g., idling or at speed or under load), and whether the engine is in an on-road vehicle, farm vehicle, locomotive, marine vessel, or stationary generator or other application. Diesel exhaust is a Group 1 carcinogen, which causes lung cancer and has a positive association with bladder cancer. It contains several substances that are also listed individually as human carcinogens by the IARC. Methods exist to reduce nitrogen oxides (NOx) and particulate matter (PM) in the exhaust. So, while diesel fuel contains slightly more carbon (2.68 kg CO2/litre) than petrol (2.31 kg CO2/litre), overall CO2 emissions of a diesel car tend to be lower due to higher efficiency. In use, on average, this equates to around 200 g CO2/km for petrol and 120 g CO2/km for diesel. The primary products of petroleum fuel combustion in air are carbon dioxide, water, and nitrogen. The other components exist primarily from incomplete combustion and pyrosynthesis. While the distribution of the individual components of raw (untreated) diesel exhaust varies depending on factors like load, engine type, etc., the adjacent table shows a typical composition. The physical and chemical conditions that exist inside any such diesel engines under any conditions differ considerably from spark-ignition engines, because, by design, diesel engine power is directly controlled by the fuel supply, not by control of the air/fuel mixture, as in conventional gasoline engines. As a result of these differences, diesel engines generally produce a different array of pollutants than spark-driven engines, differences that are sometimes qualitative (what pollutants are there, and what are not), but more often quantitative (how much of particular pollutants or pollutant classes are present in each).