Automobile combustion particles and their elimination devices. ADEME document
Results of the ADEME program since 1995 “Automobile particles”.
Physicochemical characterization of particles. Effectiveness of the depollution devices.
Despite significant progress in limiting pollutant emissions from automobiles, due to regulations and technological advances, there remains a concern over the emission of certain pollutants, such as nitrogen oxides and particles, due to the constant increase in passenger and freight traffic.
Indeed, Diesel, initially used almost exclusively for heavy vehicles, has seen its use grow very strongly for private vehicles in recent years. To date, it represents 60% of sales and nearly 50% of the fleet of private vehicles in France. This success is linked to the economic nature of the use of these engines (low diesel price associated with lower volume consumption than that of petrol engines) and to the technological progress which they have benefited in recent years.
The recent solutions implemented (high pressure direct injection, variable geometry turbocharger) have undoubtedly made it possible to increase the performance of these engines, while further reducing their intrinsic fuel consumption, pollutant emissions as well as their noise emissions.
From an environmental point of view, the diesel engine is however penalized by the particulate emissions it causes.
The study and treatment of these solid compounds, visible at the exhaust and highly criticized for their impact on air quality, is the subject of numerous characterization and development works. The particles emitted are found in suspension in the air and can be inhaled and deposit at a point in the respiratory tract or be exhaled. The deposition site, or the probability of expiration, depends on the properties of the particles, the respiratory tract and the respiratory regime. Short-term health effects are manifested at relatively low concentrations (below 50 μg / m3) and are verified at the medical level (consultations, emergency admissions).
For higher concentrations, a correlation is established between the presence of particles and the appearance of chronic bronchitis.
Regarding the longer-term effects (cardiovascular effects, respiratory tract cancer), numerous expert reports have been carried out by public health organizations in industrialized countries (IARC, 1989; INERIS, 1993; HEI (Health Effects Institute ), 1995; French Society of Public Health (SFSP), 1996…).
To date, the mutagenicity of these combustion residues has been experimentally proven.
However, the carcinogenic effects of such fumes could only be demonstrated for certain animal species and for concentrations of pollutants much higher than those encountered in the environment. In humans, epidemiological studies in the workplace tend to show an increase in the incidence of lung and bladder carcinomas.
In addition, studies conducted in the United States tend to show an increased risk of lung cancer, associated with long-term exposure to particulate pollution in the ambient air. Diesel particles have been classified as probable carcinogens by the International Agency for Research on Cancer.
The growing interest in the diesel engine, both for goods transport vehicles and for passenger cars, and the health impacts highlighted, prompt us to ask a certain number of important questions, in particular that of the relevance of the emission regulations.
In view of the fact that it is the finest particles which penetrate deep into the respiratory tract and that their harmfulness also depends on their chemical composition, the two questions which should be answered are the following:
- Will the technical devices envisaged to deal with the tightening of emission standards not have a more effective action on large, heavier particles than on finer particles, thus calling into question the relevance of the current regulations which relates to the mass of the particles emitted?
- What is the chemical composition of the particles emitted, are their dangerous compounds correctly eliminated by technical devices?
To answer these questions, ADEME decided, in 1990, to quantify the performance of a particulate filter (FAP).
At that time, the first application focused on a bus to take into account the quantities emitted in an urban environment. However, as the technology was not mature, the results were not satisfactory.
ADEME then decided to structure a major characterization program, structured around two major axes:
- A research program focused on the physico-chemical characterization of particles of automotive origin. The objectives of this program, launched in 1995 within the framework of the PRIMEQUAL / PREDIT program, aim on the one hand to inform the mechanisms of formation of these particles
and on the other hand to identify the characteristics of soot responsible for effects on health. This part is developed in the first part of the document.
- A performance evaluation program, in use on fleets, of the first systems available. The evaluations concerned all road vehicles, buses, dumpsters for household waste, heavy goods vehicles, light vehicles. For each type of vehicle concerned, all of the relevant systems are evaluated, both in real use (durability and efficiency) and in the laboratory, for precise and comparable data. This section is the subject of the second part of the document.