Air quality and local pollutants – Part 1

Health, Emission Standards And Technology

Despite the progress in emission standards, air pollution is still an issue, especially in urban areas. The world gets hotter and more populated, and multiple sources of pollution contribute to the quality of the air we breathe. Is there anything that could be done to prevent this air pollution that kills 7 million people every year globally?

Here’s what you’re going to learn in this article:

  1. Why air pollution damaging our health
  2. The emission standards that we currently rely on
  3. The technologies, which exist to limit bad pollutants

Hopefully, by the end of this article, you will be able to understand that the problem affects so many of us and it’s not just a matter of improving technologies or setting emission standards.

In the second article of these series on air quality, we will continue by covering the application of technologies in both light and heavy-duty vehicles.

The silent killer

Just because we can’t see toxic emissions, it doesn’t mean they are not polluting.

The bad air that we breathe affects our health. In fact, the effect is so strong that breathing polluted air is comparable to smoking and can lead to lung disease. That’s why it is a topic that we cannot afford to dismiss and we need solutions that can quickly introduce on the market zero and low emissions figures to move away from high polluting emitters.  Methane represents a clean alternative to petrol and diesel for transportation and it is the ideal and cleanest fuel to complement electrified solutions, such as hybrid buses and trucks. Furthermore, that same gas can be used to heat our homes or to generate power for our industries.

Polluted air is something you can’t easily escape. If you live and work in a city, you most likely community to work and back on a daily basis. Millions of Europeans are therefore affected by the impact of air pollution.

But, is transport the only reason why have bad air quaility?

Well, the transport sector is a major contributor to global anthropogenic (in other words, caused by humans) CO2 emissions. According to The International Council on Clean Transportation, 23% of those CO2 emissions are due to transport – around 8.8 GtCO2. Out of these, 6.5 GtCO2 are due to road transport, meaning light or heavy-duty vehicles. But, as important CO2 emissions are for climate change (CO2 is not classified as harmful pollutant), when it comes to air pollution, we have to look into other pollutants – Nitrogen Oxides (NOx) and Particulate Matters (PM), among some others.

So, why did we mention anthropogenic CO2 and road transport?

Because road transport remains an important source of some of the most harmful air pollutants – the NOx and PM. As a result, a big percentage of the European population is exposed to air pollutant concentrations above the World Health Organisation – WHO – air quality guidelines.

It is possible to see polluted air or bad air quality? 

Not always – just because we can’t see toxic emissions, it doesn’t mean they are not polluting or that the air quality is good. Transparent air is no indication that it is healthy. The only way you can be sure is to rely on actual measurements. For example the World Health Organisation, together with the UN, the Climate and Clean Air Coalition developed a campaign with an online pollution meter

What score does your city get? Send us a tweet with your city’s score.

What can you do to limit breathing polluted air?

The WHO recommends 5 actions:

  1. Limit walking on busy streets during high traffic
  2. Limit spending time in hotspots of traffic
  3. Don’t exercise in polluted areas
  4. Limit the use of air-polluting vehicles in highly-polluted days
  5. Don’t burn waste – the smoke from it is dangerous to your health

Emission Standards

Seeing the burden of this problem begs the question of how to reduce the negative effects caused by road transport. One instrument that we rely on is setting emission standards. The EU emission standards for exhaust emissions have become increasingly stringent over the past decades for both light and heavy-duty vehicles.

For light-duty vehicle, there are the Euro 5 and 6 standards in force since several years that set specific limits for all these pollutants. There are also driving cycles, which examine each vehicle to establish the emissions it produces and evaluate if it is acceptable according to these standards. 

In September 2018, the driving cycle test procedure was updated to the “World-Harmonized Light-duty Vehicle Test Procedure” (WLTP) for all vehicles. This update includes a new test cycle that is more representative of average driving behaviour and a test procedure that limits the allowed flexibilities and loopholes compared with NEDC (the previous test procedure).

For heavy-duty vehicles, similar cycles are in place: WHTC Transient Test Cycle and WHSC Steady-State Test Cycle. The first consists of second-by-second sequences of transient modes. It is based on on-road-specific driving patterns in trucks and buses. The second consists of a number of speed and power modes which cover the typical operating range of engines.

On both applications, the main effort done from the legislative standpoint regarding air quality is focused on the respect of the emissions standard under an operative field much wider than the only laboratory testing conditions.

The so-called Real Driving Emissions – RDE – testing conditions have been implemented to ensure the lowest emissions also a wider range of ambient conditions and driving modes. The introduction of Portable Emissions Measurement Systems – PEMS – allows to directly measure emissions while the vehicle is run on the road, reproducing the most common driving conditions.

Technologies  for better air quality

You might be wondering what are the existing vehicle technologies that can help us reduce these emissions. Here are 3 specific technologies that help with that:

The vehicle technologies 
that can help us 
reduce emissions.
  1. Three-way catalysts (TWC) operate in a closed-loop system including an oxygen sensor to regulate the air to fuel ratio. Under stoichiometric conditions, this technology ensures the effective conversion of all three major pollutants (CO, HCs and NOx) under a wide range of conditions.
  2. Selective catalytic reduction (SCR) is an advanced emissions control technology system that reduces NOx by injecting a liquid reducing agent through a special catalyst into the exhaust stream of exhaust gas. The reducing agent is usually urea, which converts NOx into nitrogen, water and CO2. The system is now normally used in Diesel applications.
  3. Diesel particulate filters (DPFs) are devices used with diesel engines to remove PM by physical filtration using a structure similar to a catalyst but with channels blocked at alternate ends. The exhaust gas is forced to flow through the walls between the channels and PM is deposited on the walls. Similar devices have been also developed for gasoline applications, especially where gasoline direct injection systems are used.

Natural gas engines are mainly based on Spark Ignited stoichiometric approach, so using TWC technologies, but recent Heavy Duty applications are also based on the Diesel cycle (e.g. HPDI system), thus presenting a DPF+SCR gas after-treatment system.  

So What’s Next?

  1. Check out the second article in these series when it becomes available.
  2. Tell us how bad air quality affects your life on Facebook, Twitter or Instagram.

Now you understand why it is so important to pay attention to the quality of air that we breathe. This is not a natural problem, but one made by humans and therefore, we need to not only implement new technologies and testing but, most importantly, change our behaviour for the future.

We must be conscious when we choose our next vehicle, when we order goods to be delivered or when we take public transport. More specifically, we need to choose and support technologies, such as natural gas, which are intrinsically clean and generate the lowest amount of pollutants.

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