André Cabrera Serrenho
University of Cambridge
André holds a BSc, MSc and PhD from the University of Lisbon in Portugal. Since 2014, he is a Research Associate in the Department of Engineering of the University of Cambridge (UK), where he has been working on material flow analysis of bulk materials.
Current European transport polices define a limit of 95 g CO2/km for the average greenhouse gas (GHG) emissions of new car sales by 2021. This is a weighted average that gives additional credits to cars with emissions lower than 50 g CO2/km. These limits are defined in terms of direct emissions, and therefore they do not consider emissions produced by electricity generation or material production. Thus, this policy leads to fostering a fast transition to electric drivetrain technologies and fails to incentivise car manufacturers to consider the potential benefits of weight reduction over electrification.
In this analysis, we examine the impacts of reducing the average weight of cars, using alternative drivetrains and promoting behaviour change on the global GHG emissions produced by the car fleet in Great Britain until 2050. This is tested using a dynamic material flow analysis of the car fleet, which estimates the composition of the car fleet, future material requirements, and material production and use-phase emissions for various scenarios. Reducing the average weight of cars can be achieved by reducing the size of cars or by changing the material composition resulting in lighter cars with the same size. Both effects are assessed in this analysis, considering different levels of downsizing and various scenarios of material composition. Various scenarios on the level of penetration of alternative drivetrains are also considered. The effect of varying average car occupancy and intensity of use in car use demand is used to examine the impact of behaviour change.
The results compare alternative options in terms of cumulative global GHG emissions from 2015 to 2050, which include direct and indirect emissions at the use-phase and material production. The results suggest that reducing the average weight of cars is able to produce greater cumulative emissions savings by 2050 than the savings obtained by incentivising sales of electric vehicles, unless there is a severe decarbonisation of the electricity grid, by approximately 50% or more by 2050. Even in a scenario of a substantially decarbonised grid, electric cars will lead to an increase in electricity demand, which makes a grid decarbonisation even more challenging. The results also suggest that if there is no decarbonisation of the grid by 2050, even if the sales of electric cars reach 100% of new sales by 2050 that would not be enough to produce any savings in cumulative emissions, unless there is a reduction in the average weight of car sales.
The results show the potential of small changes in the patterns of car use in producing substantial emissions savings. A 20% increase in occupancy and intensity of car use by 2050 (equivalent to increasing occupancy to the current levels observed in Hungary, and to car use intensity to the same levels verified in 2000 in Great Britain) could result in twice the emissions savings obtained by a complete electrification of car sales combined with alternative material composition alone.
• Socio-economic metabolism and material flow analysis , • Sustainable urban systems
