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Diesel Emissions

oil rig producing crude oil used to manufacture diesel

Crude Oil is a valuable resource used across the globe.

Diesel was invented by Rudolf Diesel, a German engineer, back in 1892.

Both diesel and petrol are refined from the same source material known as crude oil. When crude oil was first being refined in the mid 1800's it was largely for Kerosene leaving a large element of petroleum by-products remaining and it was these by-products that attracted the attention of Rudolf Diesel and the first diesel engine was finally born at the end of the 1800's.

Over 200 years later, both engines and fuel still carry Rudolf's name.

Diesel fuel releases more energy on combustion than equal volumes of petrol fuel, so diesel engines generally produce better fuel economy than petrol engines. In addition, the production of diesel fuel requires fewer refining steps than petrol, so the prices of diesel fuel has traditionally been lower than that of petrol. So, you can see the appeal of diesel engines that helped spawn their popularity, but there is a downside.

Diesel fuel has traditionally produced greater quantities of air pollutants (emissions) than petrol and over time governments have sought to reduce these by requiring extra refining steps and emission-control mechanisms be put into place to reduce the emissions which gradually narrowed the price advantage diesel had over petrol. In addition, diesel fuel emits more nitrogen dioxide per unit than petrol, offsetting some of its efficiency and price benefits with its greenhouse gas emissions.

Diesel was promoted as a more environmentally friendly fuel as part of the European Union's response to the 1997 Kyoto Protocol to reduce greenhouse gas emissions, especially carbon dioxide (CO₂). Per kilometre, diesel engines produced less CO₂ than petrol engines, but more toxic emissions.

The UK government promoted the purchase of diesel cars despite knowing the issue of toxic emissions. The problem is that governments often end up focusing on one issue at a time, such as the CO₂ output, inevitably ignoring others, such as the toxic NOx emissions. To that end, many people were incentivised to purchase diesel cars (which nowadays can be good for 200,000 miles or more) with government funded subsidies, only to now be penalised by new rules designed to curb diesel emissions. These people are rightfully unhappy.

The emissions from petrol cars can be cleaned up using a Catalytic converter, but for diesel cars it’s a little more challenging. In addition to NOx, diesel cars also produce fine particulate matter that has been linked to cancer and respiratory illnesses. Particulate filters can reduce the emissions, but they require maintaining as they are prone to clogging up (especially in vehicles undertaking only small journeys) and some vehicles require additional additives such as AdBlue.

car exhaust showing diesel smoke emissions

The UK Government encouraged the purchase of diesel cars in the early 2000's

So you could say that diesel is worse for people, but petrol is worse for the planet.

Diesel engines produce emissions in the form of Nitrogen Oxides commonly referred to as NOx which are formed during the combustion of fuel and organic material at high temperatures.

NOx is composed of nitric oxide (NO), and a smaller percentage of more poisonous nitrogen dioxide (NO2) and a range of other gases including Nitrous Oxide (N2O), Nitrogen Trioxide (N2O3) and Nitrogen Tetroxide (N2O4).

NOx can react with, amongst other things, water vapor to form Nitic Acid (Acid Rain), the inhalation of which can cause a number of breathing symptoms and which has been linked to many other illnesses. NOx is also one of the reasons for the famous smog you often see reported in places like China, but which is becoming increasingly more common in major cities across the globe.

Diesel cars produce ten times the NOx levels of a comparable petrol car.

an electric charger being plugged into a car

Whether you're a fan or not, EV cars are our future.

There is no doubt that the government encouraging consumers to purchase diesel cars through tax breaks and money back schemes in the early 2000’s was a mistake, but we are getting better at identifying and addressing environmental issues and to that end we realise that fuel sources like petrol and diesel need to go at some point. The problem though, is that the current government drive toward electric vehicles looks almost as singularly focused and possibly flawed as their previous focus on diesel vehicles.

The UK doesn’t have the electricity infrastructure to cope, is constantly being threatened with ‘brown outs’ and has moved towards more renewable sources rather than nuclear which some argue will produce less reliable sources of electricity.

In an interview on Radio 4, Lord Drayson (the former Labour Science Minister responsible for encouraging the public to invest into diesel cars) admitted that “We got it wrong. We now have a much better understanding than we did back then of what the health effects are of the by-products of diesel cars and they are literally killing people so it’s clear that in retrospect that was the wrong policy.”

Maybe we will be here in 20 years' time talking about the current government's net zero campaign by 2030 and how that too was as flawed as the 'buy diesel' campaign was in 2000! Who knows...