Future transportation: Lifetime considerations and framework for sustainability assessment
Highlight
► Cost, energy and GHG emissions throughout a vehicle’s lifetime are evaluated. ► This paper offers a structure to evaluate powertrains for whole life criteria. ► Substantial amounts of energy and emissions were evident for all options. ► Significant environmental benefits over incumbent vehicles were found. ► In-use benefits were shown to shift impacts to other phases of a vehicle’s lifetime.
Introduction
The world is becoming increasingly reliant on motorised transportation with virtually all industry, particularly in the developed world, now utilising vehicles in some way to accomplish their daily business. This has led to our current prosperity and future economic growth being dependent upon a reliable and affordable transport system. This reliance extends to personal transportation with many people now absolutely dependent on the current system, not only as a means to access everyday necessities and employment, but also to enhance recreation, facilitate learning and mobilise emergency services. The number of light duty vehicles (LDV, which is taken to encompass cars and light commercial vehicles with at least four wheels) in use across the world is set to more than double, and sales treble by 2050, as illustrated in Fig. 1.
The majority of these increases are expected to occur in the developing world, which in 2007 accounted for 85% of the global population, but only a third of the world’s car fleet (Pemberton et al., 2009).
There are however already significant problems with the present levels of vehicles, which will be exacerbated by these increases. These include:
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Supplying sufficient quantities of energy (fuel) to meet the huge demand of transportation, which is becoming increasingly problematic. The bulk of this energy is currently derived from crude oil, a finite resource, and utilised in internal combustion engines to propel vehicles.
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The emissions released during the use and production of our current transportation network. Many of these are known to have a variety of both direct and indirect detrimental effects on human health and the ecosystem. These include carbon dioxide (which is released in huge quantities, approximately 2.3 kg per litre of petrol burned), nitrogen oxides, sulphur dioxide (which both contribute to respiratory problems and acid rain) and particulate matter (which can aggravate respiratory and cardiovascular problems) (Defra, 2010).
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The vast quantities of materials that vehicle production requires, adds to the ever increasing demand on finite material resources. Between 2010 and 2050 this was estimated at over 7 billion tonnes. Allowing for the lifespan of vehicles (approximately 13 years) these same materials, some of which are hazardous, will also need to be dealt with when the vehicles reach their end-of-life.
These factors now threaten the availability and affordability of transportation which has facilitated the expansion of our mobility network in the preceding century. They indicate that the world’s current network will not be able to meet future demands in a safe and sustainable manner.
This report uses life cycle assessment (LCA) to analyse what alterations can be made to improve the energy usage, emissions, resource depletion and end-of-life issues associated with the world’s vehicle fleet, assuming that current and future levels are to be met with minimal disruption to end users.
Light duty road vehicles were specifically selected because they are the single largest contributor to personal mobility covering over 15×1012 passenger km annually (WBCSD, 2004) and constituted >94% of all road vehicle sales in 2010 (OICA, 2011). They also create the greatest demand for materials and transportation fuel, and generate the most scrap materials at the end of their lives. (It should be noted that due to the high per distance fuel consumption of commercial vehicles their aggregated fuel usage currently approaches that of LDVs in Europe, despite their lower numbers (EUROPIA, 2011)).
Section snippets
What is sustainable transportation?
'Sustainable transport can mean different things to different audiences. It can mean the cheapest point to point transport available, or reliable and predictable journeys, or the quickest means to move perishable freight, or journeys that use the least amount of energy or resources to fulfil the task. This report has focused on assessing LDVs, therefore when subsequently discussing sustainable transportation it has been considered at the fuel and vehicle level, such that;
“A Sustainable vehicle
LCA
Previous life cycle assessments (LCA) have shown that typically between 80% and 93% of a conventional vehicles life cycle energy and greenhouse gas (GHG) emissions are attributed to the production and use of their fuel, i.e., their well-to-wheels (WTW) phase (Moon et al., 2006, Volkswagen, 2008). This has led to significant amounts of research being focused on these stages, because they offer the greatest potential for savings, with the other phases of a vehicles lifetime, namely materials
Powertrains assessed
The multitude of different vehicular powertrain combinations makes it impossible to compare them all in this paper. Therefore, the examples given in Table 2 were selected to cover the main technologies. The baseline vehicles selected were amongst the most efficient in their class available in 2011, to show what can already be achieved with minimal effects to the current system and users. These values were chosen to help avoid unequal comparisons, where optimised alternative powertrain vehicles
Assessment results
Life cycle comparisons of the energy, CO2 emissions and the costs associated with the vehicles lives were determined using the methodology in Section 4. The demands of future vehicle production on raw materials and the volumes of wastes produced were also quantified.
Energy
From an energy point of view, Fig. 6 highlights the conventional diesel fuelled vehicles as having low consumptions. However, the selected combustion engines represents some of the most efficient currently available and in 2009 a vehicle achieving the average fuel consumption of diesel cars sold in Great Britain (DfT, 2010) would have an energy consumption of over 0.8 kWh/km.
The BEV charged using renewable electricity was shown to have the lowest energy consumption, over 30% less than the next
Conclusions
Increasing the lifespan of vehicles would appear at first glance to be beneficial to all aspects by abating the overall cost, emissions, and energy usage, as well as reducing the volumes of materials required to produce vehicles and those needing to be dealt with at their end of life. However, the efficiency of vehicles is anticipated to increase, which will mean their benefits over older less efficient vehicles, will at some point outweigh those gained by extending the lifespan of the vehicle.
Acknowledgements
The authors wish to thank Maxwell Pemberton, Rosemary Albinson and Allan Hutchinson for their advice in compiling this paper.
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