Exhaust emissions

With increasing emissions in densely populated areas and newly introduced environmental taxes, exhaust emissions are a closely monitored variable. Today, most manufacturers automatically provide a CO2 value in the technical data for each car. Unfortunately, carbon dioxide is not the only component of exhaust gases, what other pollutants come out of the tailpipe?

In order for a car to be homologated, it must meet a series of standards, including an important emission standard. The emission standard determines the amount of pollutants that a car can emit into the air. These regulations are based on the standards of the United Nations Economic Commission for Europe (UNECE) and the European Community (EC). As a collective designation of the emission standards, the EURO designation + the number of the standard is used, e.g. the currently applicable EURO 7. Thanks to these standards, emissions such as CO2, although somewhat paradoxically the EURO standard does not limit the amount of carbon dioxide. From 1995 to 2003, the average emissions of CO2 decreased from 186 to 164 g/km. The European Economic Commission would like to achieve a general average of 120 g/km by 2012. However, the development and production of such engines are according to car manufacturers very costly. One of the ways to support the development of ecological engines are tax and other incentives for environmentally conscious drivers.

illustrative image of exhaust gases

Most manufacturers are of the opinion that the introduction of new Euro emission standards will lead to an increase in the prices of new cars. On the other hand, the introduction of the new Euro 5 standard has reduced the amount of particulate matter in diesel engines compared to Euro 4 fivefold. Interestingly, the currently valid Euro 5 standard allows 97% less particulate matter than the fifteen-year-old Euro 1 standard.

Monitored emission components:

CO – colourless, tasteless and odourless gas, lighter than air, non-irritating and explosive; carbon monoxide binds to hemoglobin (blood pigment) 200-300 times faster than oxygen, which is thus displaced, preventing the transfer of air from the lungs to tissues – it is toxic. It is formed during incomplete combustion of hydrocarbons. In normal concentrations in the air, it oxidizes relatively quickly to carbon dioxide CO2.

CO2 – colorless gas, tasteless and odorless; not toxic, but enhances the effects of CO and contributes to the greenhouse effect. The EURO emission standard does not limit the amount of CO2. More about CO2 here.

HC – unburned hydrocarbons, containing carcinogenic aromatics, toxic aldehydes and non-toxic alkanes and alkenes, plus other components. They are formed during combustion if there is insufficient oxygen supply or if the mixture is too lean and the cylinder content does not burn sufficiently. In sunlight, they react with nitrogen oxides to form mucous membrane irritants. In summer, these substances contribute to the formation of poisonous ground-level ozone.

NOx – nitrogen oxides have similar effects as NO, NO2, attacking the lungs and mucous membranes. They are formed in the engine at high temperatures and pressures during combustion with excess oxygen. Some nitrogen oxides are harmful to health! Measures to reduce fuel consumption may lead to an increase in the proportion of nitrogen oxides in exhaust gases, as more efficient combustion leads to higher combustion temperatures. It often happens that an “ecological” turbo diesel has low CO2 emissions, but due to excessive NOx production, it only meets Euro 4 emission standards. One solution to reducing nitrogen oxides is, for example, the additive AdBlue.

SO2 – pungent, colorless, non-flammable gas, attacks the mucous membranes and lungs. It promotes the onset of respiratory diseases. Using fuel with lower sulfur content reduces the content of sulfur dioxide in exhaust gases.

Pb – Lead is a toxic heavy metal, today fuel at gas stations is commonly available only unleaded, the lubricating properties of lead are replaced by additives.

PM (Soot) – PM (Particulate Matter) particles of soot, cause mechanical irritation, act as carriers of carcinogens and mutagens.

Other Emission Components:

N2 – Nitrogen is a non-flammable, colorless, non-toxic gas without odor. Nitrogen is the main component of the air we breathe (78% N2, 21% O2, 1% other gases). The majority of nitrogen returns to the air in the exhaust gases after the combustion process is completed. A small portion reacts with oxygen and nitrogen oxides NOX are formed.

O2 – Oxygen is a colorless, non-toxic gas without taste or odor. It is essential for the combustion process.

H2O – Water in the form of water vapor, is absorbed together with air