On a daily basis, fleet vehicles travel dozens, hundreds or even thousands of kilometers and inevitably emit exhaust gases. These gases, produced by the burning of fossil fuels, not only impact the environment, as many people think, but also affect people's health and vehicle performance.
This is where exhaust gas purification comes in, an important practice that helps reduce these impacts, promoting a more sustainable future and, as a bonus, improving the operation's functioning.
How are exhaust gases produced?
What pollutants are present in exhaust gases?
What is exhaust gas purification?
Technologies for exhaust gas purification
Why is it important to clean the exhaust system?
How to purify exhaust gases?
How are exhaust gases produced?
To understand the impact of exhaust gases, it is worth first knowing how they appear. They are generated every time an internal combustion engine burns fuel, be it gasoline, diesel or any other type.
It's the same process that makes a vehicle move. During combustion, the chemical compounds present in the fuel react with oxygen to release energy, but this reaction also generates byproducts – the famous exhaust gases.
So every time the car or truck is turned on, it is producing these gases. In a fleet with several vehicles circulating daily, the amount emitted is significant, which makes it even more important to reduce the impact of these emissions.
Read more: How to reduce the emission of polluting gases from your fleet
What pollutants are present in exhaust gases?
Exhaust gases contain different types of pollutants, each of which can pose risks to our health, the environment and the climate. Let’s take a look at the main ones:
- carbon monoxide (CO)
This gas is colorless, odorless and toxic in high concentrations. It also contributes to air pollution and compromises the blood's ability to transport oxygen, which can result in health problems.
- Nitrogen oxides (NOx)
These compounds help form acid rain and smog (polluting fog). In addition, they affect the respiratory system and contribute to environmental degradation.
- Solid particles (MP)
Particulate matter is composed of microscopic particles that, when inhaled, can cause negative impacts on air quality and, consequently, respiratory and heart diseases.
- Hydrocarbons (HC)
These volatile organic compounds, when they react in the atmosphere, help to form tropospheric ozone, which is also associated with respiratory problems, then it is harmful to human health.
- Carbon dioxide (CO₂)
Although it is not directly toxic to humans, is mainly responsible for the greenhouse effect, contributing to climate change.
Read more: Sustainability in fleet management: 7 steps to a successful ESG implementation
What is exhaust gas purification?
Exhaust gas purification is a method that helps clean the gases that come out of the exhaust system, reducing the pollutants it releases into the air. Think of it as a smart filter: It does not allow harmful particles and substances to be released directly.
In other words, it is a way of protecting both the environment and people's health, but in the fleet, This goes beyond just meeting requirements and regulations: It is a practice that helps to optimize vehicle performance and can also reduce costs.
Technologies for exhaust gas purification
The risk involved in the emission of exhaust gases is great. On the other hand, thanks to advances in technology, there are several solutions to purify these gases and minimize their impacts. Here are the main ones:
- 3-Way Catalyst
Used in many gasoline vehicles, It transforms carbon monoxide, nitrogen oxides and hydrocarbons into less harmful substances. It is one of the most common technologies, you can even hear the catalytic converter working when the vehicle is on.
- Diesel Particulate Filter (DPF)
This filter captures solid particles from the exhaust gases of diesel vehicles. However, it needs to be cleaned regularly, or it can become clogged. There are automatic regeneration methods that burn these particles, ensuring its continued operation.
- Urea injection system (SCR)
Here, a reagent such as urea is used to transform nitrogen oxides into nitrogen and water. This technology is quite effective in fleets, significantly reducing NOx emissions.
- Exhaust gas recirculation (EGR)
In this process, part of the engine exhaust gases are burned again, reducing the amount of NOx released. This is especially useful in diesel-powered vehicles.
Why is it important to clean the exhaust system?
Exhaust system cleaning and exhaust gas purification are practices that benefit both the company and the environment. Here are some reasons why:
- Fleet performance
A dirty exhaust system can lead to engine problems, such as increased fuel consumption and lower power. Regular purification prevents these problems and helps the engine run more efficiently.
Read more: Fuel economy: 8 tips to reduce fleet expenses
- Environmental regulation
In many places, there are strict regulations on vehicle emissions. With regular maintenance and the use of purification technologies, You ensure your fleet is in compliance and avoid fines.
- Public health protection
Many pollutants are associated with respiratory diseases, cardiovascular diseases and cancer. Reducing emissions means fewer pollutants in the air, which helps to preserve the health of employees, drivers and the general population.
Read more: Corporate Social Responsibility: what it is, benefits and tips for implementation
- Air quality and impact on climate
By reducing the harmful effects on the environment, ecosystems and biodiversity, the air we breathe is of better quality. Not to mention that it is a way of mitigating the effects of climate change and global warming.
How to purify exhaust gases?
Now that you understand the importance of cleaning exhaust gases, we can discuss how to keep your exhaust system consistently clean and efficient.
The process can vary depending on the type of emission source and pollutants. So here is a general step-by-step guide that includes the use of an emissions control system, the 3-way catalyst:
1. Collection of exhaust gases
After combustion in the engine, the gases resulting from this process are collected by the exhaust system. It channels the gases from the engine to the emissions control system, where purification takes place.
2. Monitoring gas composition
Sensors analyze the composition of the gases to identify the amount of pollutants, such as nitrogen oxides (NOx), carbon monoxide (CO) and hydrocarbons (HC). This is crucial to adapt the purification process to the actual emission conditions of each vehicle.
3. Gas pretreatment (optional)
In some fleets, gases may undergo pre-treatment, which removes larger particles and other impurities before they enter the emissions control system. This is more common in diesel vehicles, where specific filters help capture particulate matter.
4. 3-Way Catalyst
Most gasoline-powered vehicles use a three-way catalytic converter in the exhaust system. This catalyst is so named because it performs three fundamental reactions:
- NOx reduction
The catalyst transforms nitrogen oxides (NOx) into nitrogen (N₂) and oxygen (O₂).
- Oxidation of CO and HC
Carbon monoxide (CO), a toxic gas, is converted to carbon dioxide (CO₂), and hydrocarbons (HC) are also oxidized to become CO₂ and water (H₂O).
5. Electronic engine control (ECM)
The ECM module constantly monitors engine performance and the operation of the emission control system, adjusting the fuel mixture and other variables to improve combustion efficiency and reduce emissions.
6. Urea injection system (SCR)
In diesel-powered vehicles, especially trucks, an SCR can be used to further reduce NOx. Urea is injected into the exhaust gases and reacts with the NOx, forming nitrogen and water – substances that are much less aggressive to the environment.
7. Continuous monitoring
Sensors monitor the flow of gases in real time to verify that the emissions control system is operating within ideal parameters. This constant monitoring allows for automatic adjustments, ensuring efficiency in reducing pollutants.
8. Regular inspection and maintenance
Finally, it is essential to keep an eye on the emissions control system to ensure that it continues to function properly. During these inspections, system components (such as the catalytic converter and particulate filter) are checked for wear or failure.
Structure a good fleet maintenance plan and not leaving these reviews out ensures that the system operates correctly and that the vehicle emits fewer pollutants, an essential practice for anyone who wants to keep a fleet operating successfully.
Read more: Sustainable maintenance: what it is and how to apply it in fleet management
As a fleet manager, you can make a big difference by taking these precautions, ensuring that your vehicles run cleaner. To help you with this task, we have put together a complete eBook on preventive maintenance.
