Powertrain Technologies to Beat Global Warming: Hybrid or Diesel?

Concerns over global warming have in recent years prompted governments around the world to focus on reducing greenhouse gas emissions, CO2 in particular. As transport accounts for a significant proportion of overall greenhouse gas emissions, improvements in this sector are a priority. Europe has been pro-active in this respect and enacted a voluntary agreement back in July 1998 between the European Union and the European Automobile Manufacturers, putting in place targets to reduce the European CO2 fleet average from 180 g/km in 1998 to 140 g/km CO2 by 2008, with a further reduction to 120 g/km by 2012.

The best solution that European car companies found to attempt to achieve these targets was to increase the proportion of diesel vehicles (which have on average 35 per cent greater fuel economy than gasoline analogues) that they manufactured. As a result the market share of diesel passenger cars in Western Europe grew from a quarter in 1998 to almost 50 per cent in 2005. Several factors helped to achieve diesels’ success including: favourable taxation systems and savings on fuel as well as significant improvements to engine power and performance.

A newer technology is that of hybrid vehicles, whereby the car has two power sources – one being the conventional fossil fuel (gasoline or diesel) and secondly an electric battery. With rising fuel prices and increasing pressure on countries such as the USA to lower CO2 output, the question on many people’s minds now is: will the market for hybrids increase, or will diesels be the preferred powertrain for containing CO2 emissions, in particular for US car manufacturers and purchasers?

In the last 5 years since their introduction, hybrid sales in the US have grown to 250,000 vehicles according to the Massachusetts-based automotive consultancy – Global Insight. However, this growth in hybrid sales is expected to level off in the next couple of years, as the fuel-economy benefit on-highway has not been as good as expected. This is largely because the vehicle does not run on the battery at highway speeds of 50-60 mph and fuel economy is then determined by the gasoline engine alone. Considering the high vehicle cost premium for a hybrid of between 40-60 per cent over an analogous gasoline, consumers are beginning to question the benefit of driving a hybrid. Meanwhile, diesel vehicle sales in the US reached around half a million in 2005. Consumer acceptance of diesels is slowly improving due to increasing fuel prices and careful marketing of the benefits of diesel models, which, compared to hybrids, have much smaller price premiums over similar gasoline vehicles.

Further improvement in hybrid technology over the next few years is expected to see renewed growth in demand for these vehicles and they are forecast to reach a sales share in the US of 4 per cent (0.75 million vehicles) in 2011. Innovations in diesel and the availability of models that can meet future legislation ought to ensure steady growth in demand for diesel cars, reaching 7 per cent of sales in 2011.

Growth in diesel and hybrid markets globally will continue to have a positive effect on demand for platinum group metals (PGM). In the case of certain hybrid models, the repeated cold-starts in urban driving (when the battery is the main power source and the engine is frequently switched off) mean that the catalyst requires more PGM than a standard gasoline catalyst. Diesels also require advanced aftertreatment to meet current legislation including the use of a platinum-coated trap to capture and destroy emissions of fine soot particles, while in the longer term they future they are likely to need an enhanced catalyst system for the control of nitrogen oxide emissions.


Chart Source: Global Insight