Emissions assessment

In principle, environmentally relevant emissions arise in all phases of the vehicle life cycle. Known as greenhouse gas emissions, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O, also called laughing gas) in particular contribute to the global greenhouse effect and therefore cause indirect damage to humans and nature. In addition to the greenhouse gases, numerous substances with direct negative effects on nature and human health are emitted (pollutants). While greenhouse gases have a global effect – i.e. they are unrelated to the place where they are emitted – pollutants come down hard on the area in which the emissions occur. Pollutants can cause harm to significantly more people in densely populated areas than in open countryside. Important pollutants are particles (particulates, PM), nitrogen dioxide (NO2, and/or together with nitric oxide (NO) also listed as NOx), carbon monoxide (CO), hydrocarbons (HC) and sulphur dioxide (SO2).

Environmental effect categories

The various emitted materials and substances are responsible for different – and sometimes overlapping – effects. To assess these effects in summary, certain environmental effect categories are used in environmental records. These weight the individual components as a single factor that describes the severity of the environmental effect. Important categories are:

  • Climate impact

    Our climate is influenced by the greenhouse effect, to which both natural and man-made greenhouse gas emissions contribute. Artificially intensification of the greenhouse effect leads to global warming, which poses risks for humans and nature. The most important greenhouse gases additionally emitted through human activity are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O, also called laughing gas). However, their effects are very different. To summarise the climatic effect of a process, greenhouse gas equivalents are used that give the climatic effect in comparison to carbon dioxide. So methane has a greenhouse potential of 25 – i.e. it contributes to the greenhouse effect 25 times as strongly as carbon dioxide. The greenhouse potential of laughing gas is 298 (IPCC, 2007).

  • Acidification

    Acidification means a reduction in the pH level and can be both a natural process or be caused or accelerated by human activity. Emissions of hydrochloric acids, sulphur dioxides, hydrogen sulphides, nitrous gases and ammonia are the worst offenders. Acidification can occur in bodies of water and in the soil (acid rain) and it restricts plant growth and reduces agricultural yields.

  • Eutrophication

    Eutrophication represents an excess of nutrients both in water and in soil. Phosphates and nitrates are the primary causes and they are usually applied by humans, e.g. for fertilisation in agriculture. This over-fertilisation and/or supernutrition of plants and other organisms (e.g. algae) leads to increased productivity but is also linked to oxygen depletion. As water and soil are affected in very different ways, there is often a division of environmental effects into the categories of water eutrophication and soil eutrophication. Simplistically, it is assumed that all nutrients emitted into the air represent an over-fertilisation of the soil and all nutrients emitted into the water contribute to an over-fertilisation of the water.

  • Summer smog formation

    Summer smog can be described as a high concentration of ozone close to the ground. Ozone is a harmful trace gas that leads to damage to vegetation and other materials and causes health problems. Ozone formation is supported by UV radiation, i.e. by sunny weather, which gives it the name summer smog. The environmental effect of summer smog is given as POCP (Photochemical Ozone Creation Potential). Photooxidants are reactive substances and can trigger a variety of chemical reactions in the environment that contribute to air pollution.

  • Particulates

    A range of international studies show that an increase in particulate concentration goes hand in hand with a marked increase in death rates from respiratory and cardiovascular diseases. New studies by internationally recognised organisations – currently the WHO – have confirmed a high mortality risk from particulates.
    Particulates are dust with particles with a diameter of less than 10 micrometres (µm) and are therefore also referred to as PM10 (Particulate Matter < 10µm).