Researchers from the International Council on Clean Transportation (ICCT) compared the life-cycle emissions of electric, hydrogen, natural gas and diesel trucks and buses in Europe.
Battery electric models were found to be able to deliver the greatest emission reductions even when using the EU's average electricity grid mix, which is currently not fully renewable but is expected to improve during the lifetime of the vehicles.
To meet Paris Agreement goals, Europe urgently needs to decarbonise its trucks and buses, which are the highest emitting vehicles on the road. While they represent only 2 per cent of road vehicles, they contribute around a quarter of transport-related emissions.
The methodology in the study addresses not only CO2 emissions resulting from vehicle tailpipes but also the emissions arising from the manufacturing of the vehicles and their components, vehicle maintenance, fuel production and electricity production.
It also factors in estimated changes in the average electricity and fuel mix during the lifetime of today's vehicles.
The greatest climate impact produced by trucks and buses over their whole life comes from the use or fuel consumption phase, not from the extraction of raw materials, construction or maintenance, the study found.
"The problem is not the factory but the road. The high greenhouse gas intensity of driving a truck during its whole life offsets the greenhouse gas emissions generated during manufacturing or the production of the fuel, or the energy it consumes. Our study addresses the uncertainties surrounding the share of emissions in all stages of the vehicle's life. It shows that only battery electric and some fuel cell electric trucks can meet the climate targets in the sector," said Nikita Pavlenko, ICCT's fuels program lead.
The estimated emissions produced over the whole lifetime of a battery-electric 40-tonne tractor-trailer entering service in 2021 were found to be "at least" 63 per cent lower than diesel. As the grid continues to decarbonise, the emissions of these will fall further – the study shows an 84 per cent reduction when using only renewable electricity.
Fuel cell electric trucks using hydrogen produced from fossil fuel produce 15 per cent less emissions compared to their diesel counterparts. The reduction depends heavily on the source of hydrogen. If the fuel is produced with only renewable electricity, emissions fall by 85 per cent, although the savings from hydrogen trucks are less than can be achieved from a battery electric model when using a non-renewable energy source.
In the various scenarios, natural gas trucks and buses provide, at best, marginal emission reductions compared to diesel. 2021 vehicle models were found to have life-cycle emissions ranging from 4 to 18 per cent lower than their diesel counterparts.
Methane, which is a potent gas that leaks from the vehicle and throughout the production and supply of natural gas, is a significant driver of the powertrain's emissions. However, the benefits from natural gas vehicles disappear when looking at short-term warming impacts, which result in 0 to 21 per cent greater emissions than diesel vehicles over natural gas trucks' full lifecycle.
