Bronte Wells
Diesel cars have been the subject of much controversy in recent times, with some governments even planning to ban them from urban areas. This is due to the amount of toxic emissions they produce, which can be extremely harmful to human health. While diesel engines are lean-burn, meaning they use less fuel and more air than petrol engines, they produce higher levels of particulate matter, which has been linked to poor heart health and increased hospital admissions. However, the comparison between diesel and petrol engines is complex, and some sources argue that modern diesel engines are very clean and that the health risks have been overstated. So, how much more polluting are diesel cars?
| Characteristics | Values |
|---|---|
| Pollution compared to petrol cars | Diesel vehicles cause more than four times the pollution than petrol cars. |
| Toxic emissions | Diesel cars produce higher levels of toxic emissions. |
| Fine particulate matter | Diesel engines emit higher levels of fine particulate matter, which is associated with poor heart health. |
| CO2 emissions | Diesel engines produce lower CO2 emissions, but this advantage is offset by higher emissions of other pollutants. |
| NOx emissions | Diesel engines generally have lower NOx emissions, but some models emit up to 15 times the laboratory limits when used in real-world conditions. |
| Maintenance | Diesel engines require more maintenance, such as the regular addition of a urea mixture to the engine. |
| Fuel efficiency | Diesel engines are lean-burn and use less fuel than petrol engines for the same performance. |
| Health impact | Diesel emissions have a negative impact on human health, including increased stroke rates and heart attacks. |
| Public perception | Diesel cars have received negative publicity due to their emissions, leading to a decline in sales. |
| Government response | Some governments plan to discourage the use of diesel cars or ban them from urban areas. |
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What You'll Learn
Diesel cars produce more toxic emissions than petrol cars
Diesel cars have received negative press in recent years due to the volume of toxic emissions they produce. Some governments are even considering banning them from urban areas. This backlash comes despite diesel being promoted as a more environmentally friendly fuel as part of the EU's response to the 1997 Kyoto Protocol, which aimed to reduce greenhouse gas emissions.
While diesel engines are "lean-burn", meaning they use less fuel and more air to achieve the same performance as a petrol engine, they produce higher levels of particulates. These microscopic bits of soot are left over from the combustion process and can penetrate deep into the lungs, causing irritation and potentially triggering asthma attacks. The smallest of these particles, known as "ultrafine" particles, are the most dangerous as they can enter the bloodstream and cause an increased risk of strokes and heart attacks in susceptible individuals.
Research has proven that increases in background concentrations of particulate matter result in more hospital admissions and deaths from heart attacks, particularly among those already at risk. This has led to a disconnect between air pollution policy and climate change policy, as the focus on reducing CO₂ emissions has come at the cost of human health. While diesel engines produce lower CO₂ emissions, they emit more toxic pollutants, with some studies showing that they cause over four times the pollution of petrol cars.
It is worth noting that not all diesel engines are the same, and some models compare favourably to petrol equivalents. Well-maintained, newer diesel vehicles have similar levels of particulate emissions to petrol cars, although they are still higher. The introduction of mandatory on-road emissions testing in the EU is expected to bring down emissions levels, and manufacturers are also working to make petrol engines more efficient. However, the current consensus is that petrol vehicles are, on average, less polluting than diesel.
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Diesel engines are lean-burn and use less fuel
Diesel engines are "lean-burn", meaning they use less fuel and more air to get the same performance as a petrol engine. Lean-burn engines have a much higher air-to-fuel ratio, which can be as high as 65:1, compared to 14.64:1 for stoichiometric gasoline combustion. This higher ratio results in lower fuel consumption and fewer hydrocarbon emissions.
The lean-burn approach was first introduced by Chrysler in 1976 with their Electronic Lean-Burn (ELB) system, which used spark control and engine parameter sensing strategies. This system was produced in both open-loop and closed-loop variants, with the latter using an oxygen sensor and a feedback carburettor to meet increasingly stringent emissions regulations. Lean-burn engines do not work well with modern 3-way catalytic converters, which require a pollutant balance at the exhaust port. Instead, they often use a complex catalytic converter system to reduce NOx emissions.
The main advantage of lean-burn engines is their improved fuel efficiency, which can be up to 20% higher than that of stoichiometric gasoline engines. This is achieved through higher compression ratios, which also result in improved performance and lower exhaust hydrocarbon emissions. However, one drawback of lean-burning is the need for a complex catalytic converter system to reduce NOx emissions.
While diesel engines are lean-burn and use less fuel, they have been criticised for producing more toxic emissions than petrol engines. Fine particulate matter emitted from diesel engines is associated with poor heart health, and the higher levels of NOx emissions can also have negative health and environmental impacts. Overall, while diesel engines may have lower CO₂ emissions, their impact on human health and the environment through other types of emissions is a significant concern.
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Diesel cars are more damaging to human health
Diesel cars have been the subject of much negative publicity due to the volume of toxic emissions they produce. Some governments are even planning to discourage their use or ban them from urban areas. This is because diesel engines produce higher levels of particulates, microscopic bits of soot left over from the combustion process. These particulates can penetrate deep into the lungs, causing irritation and potentially triggering asthma attacks. The greatest danger lies with the smallest particles, known as "ultrafine" particles, which can get to the surfaces where oxygen enters the blood and even enter the bloodstream. They can cause an increase in stroke rates and heart attacks in people with underlying health conditions. Research has proven that increases in background concentrations of particulate matter result in more hospital admissions and deaths from heart attacks, particularly among those already at risk.
While diesel fuel contains slightly more carbon (2.68kg CO₂/litre) than petrol (2.31kg CO₂/litre), overall CO₂ emissions from a diesel car tend to be lower. This is because diesel engines are ""lean-burn", meaning they use less fuel and more air to get the same performance as a petrol engine. However, diesel engines produce more NOx emissions, and these emissions have been found to be much higher when driven on the road than in laboratory tests.
It is worth noting that some diesel models do compare favourably with their petrol equivalents, but they are currently in the minority. Well-maintained diesel vehicles have similar levels of particulate emissions to petrol cars, although they are still higher. In addition, diesel engines generally pollute much more in real-world conditions than official statements from manufacturers suggest, despite the presence of filters.
The promotion of diesel as a more environmentally friendly fuel option in the EU's response to the 1997 Kyoto Protocol has led to an increase in the number of diesel vehicles on the road. This has resulted in more damage to human health, as the health impact of fine particulate matter emitted from diesel engines is significant. Overall, while diesel engines may have lower CO₂ emissions, they are more damaging to human health due to the toxic emissions and particulates they produce.
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Diesel engines produce higher levels of particulates
DPM levels are expected to decline as additional controls are adopted and the number of new technology diesel vehicles increases. However, currently, most vehicle fleets are dominated by older, more polluting vehicles, which will remain in operation for many years, continuing to damage human health.
The higher levels of particulates in diesel exhaust are due to the combustion process and the nature of diesel engines. Diesel engines are ""lean-burn", meaning they use less fuel and more air than petrol engines, but the high temperatures and pressures of the combustion process result in the significant production of NOx (gaseous nitrogen oxides). While total nitrogen oxides from petrol cars have decreased by around 96% through the adoption of exhaust catalytic converters, diesel cars still produce nitrogen oxides at similar levels to those of 15 years ago.
To reduce particulate emissions, diesel engine manufacturers have turned to technologies such as particulate filters, which can clog when used mainly for urban driving, and the addition of a urea mixture to the engine. However, these technologies can be costly and require more maintenance and driver input.
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Electric motors are the only engines that reduce CO2 emissions
Diesel cars have been subject to negative publicity due to their toxic emissions. Some governments are even planning to ban them from urban areas. Diesel engines are "lean-burn", meaning they use less fuel and more air to achieve the same performance as a petrol engine. While diesel fuel contains slightly more carbon per litre than petrol, overall CO2 emissions from a diesel car tend to be lower. However, diesel vehicles produce more than four times the pollution of petrol cars.
Electric vehicles (EVs), on the other hand, produce zero tailpipe emissions and are responsible for significantly fewer greenhouse gas emissions during operation. They are also more energy-efficient, using 87-91% of the energy from the battery and regenerative braking to propel the vehicle, compared to gasoline vehicles, which only convert about 16-25% of energy from gasoline into movement.
However, it is important to consider the emissions associated with the production and charging of electric vehicles. The manufacturing of electric motors and batteries can contribute to CO2 emissions, especially if produced in a fossil fuel-burning facility. Additionally, the electricity used to charge EVs may create carbon pollution, depending on the energy sources used in the local power grid. Nevertheless, as more renewable energy sources are adopted, such as wind and solar, the total GHG emissions associated with EVs can be significantly reduced.
In summary, while electric motors are a crucial step towards reducing CO2 emissions, it is important to acknowledge that their production and charging can contribute to carbon emissions. However, over the lifetime of the vehicle, EVs are generally responsible for lower GHG emissions compared to gasoline or diesel cars.
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Frequently asked questions
Yes, diesel cars produce more pollution than petrol cars. Diesel engines produce higher levels of particulates, microscopic bits of soot left over from the combustion process. These particulates can be harmful to human health, increasing the risk of heart attacks and strokes.
Diesel engines are “lean-burn”, meaning they use less fuel and more air to achieve the same performance as a petrol engine. This results in lower carbon dioxide emissions, but higher emissions of other pollutants.
Manufacturers have installed particulate filters to comply with new, more restrictive standards on diesel particulate matter pollution. These filters can remove between 90 and 99% of polluting mass particles. However, they are not effective at retaining the finest and most dangerous particles produced by diesel engines.
