How environmentally friendly are hybrid vehicles actually?

How environmentally friendly a hybrid vehicle is, depends on a great many variables, not least the way in which the boundaries of assessment are drawn. What is often overlooked is the fact that the effectiveness of plug-in hybrid vehicles in terms of their environmental impact depends largely on the levels of driving and charging discipline end users are able to exercise.

For example, pressing heavily on the gas pedal, as opposed to driving in a more measured manner, can lead the battery power to deplete more quickly, particularly in the case of large SUVs or luxury vehicles – which are commonplace in this category – and so bring the hybrid into ICE mode more quickly.

In any case, longer journeys will inevitably lead to the increased use of the internal combustion (ICE) element of the vehicle due to range restrictions, which in the case of heavier vehicles means far higher fuel consumption in ICE mode. If we consider the added weight of a battery and additional electric drive components in this scenario, efficiency levels are greatly reduced.

Evidence also suggests that large numbers of hybrid users do not charge their battery on a regular basis, which essentially means they are driving an ICE vehicle even on shorter journeys.

Setting the boundaries of the pollution assessment strongly determines the result when evaluating the environmental friendliness of a hybrid vehicle.

For example, if we look at what we call the ‘tank to wheel’ evaluation, a hybrid vehicle used to its full potential might outperform an ICE alternative from an environmental perspective.

However, if we expand our thinking to look at ‘well to wheel’ (as in oil well), we start to see a different picture emerging. Where did the energy come from that was used to charge the battery?

If that energy was produced by green sources – such as wind or solar – then the hybrid may be the greener option. However, if that energy came from a fossil fuel power plant, using coal or gas, for example, the negative environmental impact is simply being shifted to another area.

The most realistic evaluation comes from what is known as a ‘cradle to grave’ lifecycle assessment perspective – as this gives us a true picture of the environmental impact in its entirety. Here we must open our minds even further, as the scope broadens even more significantly.

Electric hybrid vehicles require rare earth elements, which in themselves have an environmental impact in terms of how they are extracted and processed. Also the production of the battery is very energy intensive and needs to be included in the entire balance sheet.

At the end of the vehicle’s life, is the recycling or scrapping process more complex and intensive as a result of those materials? Often, it is. The point is, there are a wide range of elements that must be factored into the environmental equation that are often not commonly conveyed to the end user.

Then there is the aforementioned size issue. If a small hybrid city car is being used for short journeys in built up towns or cities then this will be favorable environmentally as – assuming the vehicle is charged regularly and driven responsibly – it will use its electric power source, which will in turn have an impact on emissions and air quality in the surrounding area. If the vehicle is a two-ton SUV being used for longer journeys, then the hybrid element is often insignificant as the ranges required means the reliance will be on the ICE powertrain.

This fact begs the question, should more hybrid vehicles use diesel engines as opposed to petrol?

The case for diesel is a compelling one, particularly for those that undertake regular long journeys, as it is a far more efficient fuel source which, when combined with highly effective catalytic reduction systems, can produce low emissions levels. It is a hard sell to end users, however, as diesel engines are often more expensive in the first instance and many options have therefore been removed from the options lists of hybrid producers.

Datwyler is a proponent of the use of diesel hybrids, and is highly active in the area of Selective Catalytic Reduction (SCR) systems for diesel engines, which use water-based urea solutions (AdBlue® or Diesel Exhaust Fluid (DEF) as it is known in the USA) as an ammonia source to neutralize the nitrogen oxides in exhaust emissions.

In SCR systems, ammonia (NH3) reacts selectively with nitrogen oxides, resulting in harmless nitrogen and water.

To guarantee the safe transport of these chemicals from their storage tank to the exhaust system, the SCR technology requires parts that are based on specifically designed elastomer materials that are exposed to and attacked by AdBlue®.

Datwyler components are used extensively for these purposes in Selective Catalytic Reduction (SCR) systems, and the company is also active in other areas that have the potential to increase the environmental efficiency of hybrid vehicles.

As we have seen, the effectiveness of hybrid vehicles in terms of their impact on the environment – including air quality – depends on whether they are used in the correct manner by the people who elect to purchase them. The boundaries need to be clear as to how efficiencies are measured, and also the education process needs to be clear to ensure there is a clear understanding of how to get the best out of the technology in the way it was intended to be used.

Simply buying a hybrid vehicle will not have much of an impact if it is a heavy SUV that is not charged and then used on a 300km journey. A smaller, city based car that is regularly charged and used on short urban journeys will be a different story.

By Andreas Minatti, Head of Business Development at Datwyler

This article first appeared in the March 2021 edition of Industrial News.