Life-Cycle emissions: Going beyond Well to Wheel

It is finally time to talk about Life-Cycle emissions and see how they differ or rather upgrade upon the partial understanding from the Tank-to-Wheel and Well-to-Wheel emissions. In our previous two articles, we started a deep-dive into explaining what vehicle emissions are, how are measured and why it is important to understand what all the different tools mean. Let’s take a look at the Life-Cycle Assessment (LCA).

With the Life-Cycle Assessment – we aim for a more complete evaluation of the emissions associated not only to the use of the vehicle but also to its manufacturing process and to the so-called “end of life” (vehicle dismantling and material recycling).

This view gives us an estimation over the entire lifetime of the vehicle. According to ACEA statistics, the average lifetime of passenger cars in the EU is 10.5 years, with an average mileage of 15,000 km per year, meaning an overall mileage of 160,000 km. 

Why is it important to the average life of a vehicle?

For as long as the transport system has been based on conventional technologies, like the Internal Combustion Engine – ICE – configurations, the manufacturing and end of life processes were quite similar. 

Why is it important to the average life of a vehicle? Emissions during the whole life of the car should be measured and compared.

In the current scenario, with a progressive penetration of the electrified architectures, the LCA approach is very important as electrified solutions are critical with regard to two aspects :

  • The energy intensity of the batteries manufacturing process
  • The recycling of batteries, particularly important due to the scarcity of materials like Lithium, Cobalt and Nickel, used to make the car battery

A recent study based on a wide literature review published by the IVL Swedish Environmental Research Institute indicates that the highest CO2 footprint of the Lithium-ion batteries comes from the manufacturing process.

IVL Swedish Environmental Research Institute findings:

Findings from IVL Swedish Environmental Research Institute

This means that a vehicle equipped with a 75 kWh battery pack, assuming an average value of 90 kg CO2/kWh from the table above, will emit 6,750 kg of CO2 only for the manufacturing of the battery pack.

Is this a significative amount of CO2? 

Let’s run a comparison of the GHG emissions considering all the steps as indicated in the figure below (a life-cycle approach): 

Life-cycle of a vehicle includes manufacturing, fuel, tailpipe emissions and end of its life

If we consider a C-segment vehicle (typical car on the European city streets), representative of the EU market today, we can expect the following tailpipe (TTW) emissions:

  • Petrol: 115 g/km
  • Diesel: 102 g/km
  • Petrol HEV: 85 g/km
  • Petrol PHEV: 40 g/km
  • CNG: 94 g/km

Remember, the tailpipe emissions (aka Tank-to-Wheel) are those that the vehicle produces. This measurement, on which the regulations are based, doesn’t count the emissions of the fuel.

At the same time, for the BEV we have considered an energy consumption of 14.5 kWh/100 km, with a current EU energy mix of 106 g CO2/MJ and a forecast by 72 g CO2/MJ in 2030.

Are Battery-Electric Vehicles truly 'zero-emissions'?

So let’s put it all together. The figure below shows all emissions: manufacturing, fuel (Well-to-Wheel), burning the fuel by the car (Tank-to-Wheel) and end-of-life of the vehicle. This is the only way to truly compare emissions from different vehicles.

The reason by the Battery-Electric Vehicle doesn’t have any emissions in the Tank-to-Wheel category is because it doesn’t burn fuel to move – it uses a battery instead. But, contrary to popular belief, that doesn’t mean that is a zero-emissions vehicle (regardless of the manufacturer and model).

When are Battery Cars ‘Zero-Emissions’?

The Battery-Electric Vehicles (BEVs) are only ‘zero-emissions’ when we just consider tailpipe emissions, not life-cycle. In fact, the emissions from the vehicle manufacturing process are approximately twice those from conventional vehicles. On top of this, Well-to-Tank emissions are also much important. Certainly, thanks to the higher powertrain efficiency, BEVs perform better than other solutions but nevertheless, that doesn’t make them ‘zero-emissions’.

LCA engine comparison of GHG emissions.

How is emissions performance affected when we consider renewable gas (considering a life-cycle analysis)?

Let’s compare different energy carriers, like fuels but also electricity or some combination (like PHEV and HEV). Here we present how the overall results in terms of LCA change when we consider the options coming from renewable gas production, as well as from renewable energy production.

LCA comparison based on the whole life-cycle of the vehicle

By doing that, you can discover that renewable gas is an easy way to drastically reduce the LCA figures, thanks to the negative Well-to-Tank emissions. We’ve already talked in a previous article why renewable gas offers a negative impact and is actually a solution which can already decarbonise transport effectively.

The following figure provides the overall result from the different technologies considered:

LCA GHG emissions comparison over the whole lifetime of the vehicle

What’s the implication by all this and why is the life-cycle analysis important?

Certainly, this analysis has to be considered as a starting point when setting policy actions and regulations aiming to decarbonize the transport sector. Some considerations:

  • Due to the battery manufacturing footprint, PHEVs (plug-in hybrid vehicles) are more or less equivalent to HEVs (hybrid vehicles)
  • CNG (fossil) solution results equivalent to HEV and PHEV
  • Considering the energy mix in 2030 for electricity production, BEVs are expected to produce approximately half of the CO2 from conventional fuel vehicles. This assumes no need to replace the battery over the entire vehicle lifetime
  • Feeding a CNG vehicle with biomethane produced from municipal waste and/or with synthetic gas leads to the same low amount of emissions as a BEV under the assumption of always running on electricity from wind or solar energy
  • Using biomethane from liquid manure is a very pragmatic way to generate negative carbon emissions. 

This means that, when running, a CNG vehicle can contribute to capturing CO2 from the atmosphere….a very affordable way to implement the so-called Carbon Capture and Utilisation – CCU – process.

In summary, transport decarbonisation is an important topic that needs to be examined in-depth and comparing vehicles just based on their Tank-to-Wheel emissions can be very misleading. 

Now you know how to better understand this topic of vehicle emissions and what the current debate is. 

Future regulations will hopefully look into the complete picture from an LCA perspective in order to provide us with the right information, not based on a partial view, but on real and complete data and information.

If you missed our previous two articles in these series about emissions, here is a quick link to both of them:

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