Universiteit Leiden

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Environmental benefits in transport sector often disappointing

Eco-innovations like more economical cars do not generate the environmental benefits predicted by the manufacturers. This is the result of the so-called rebound effect, concludes Leiden industrial ecologist David Font Vivanco on the basis of new algorithms. PhD defence 3 March.

The transport sector is responsible for more than 20 per cent of the greenhouse gases that contribute to climate change. Innovations in the sector have the potential of generating significant environmental benefits. When manufacturers introduce new products, they try to predict the total environmental impact in advance, on the basis of lifecycle analyses, for example. However, in practice the environmental benefits that they predict using these methods often fall short of expectations.  


Trip to Indonesia

Font Vivanco explains that the rebound effect means that the anticipated energy savings are partly or even completely cancelled out because of other dependent factors. He gives an example: 'Manufacturers develop cars that use fuel more efficiently, in order to achieve greater energy savings. The users therefore save money on fuel. In general, they spend the money they have saved on more car trips, or a trip to Indonesia, maybe. The result is that the energy savings are partly cancelled out.' 


Savings

Scientists want to be able to predict how people spend the money they have saved from energy efficiency, so that they can factor in the environmental effect. Font Vivanco: ‘The easiest way to find out is to ask people, but, as with the example of emissions, they generally don't know the answer. The alternative is to try to explain it using historical data, or statistics.' 


Diesel cars

Font Vivanco analysed whether diesel cars have any environmental benefit, and if so, what that benefit is. 'I discovered that the rebound effect is greater than the literature leads us to expect. So how is that possible?' He found that the different methods for calculating the rebound effect produced very different results. 'That led us to develop a new definition: the environmental rebound effect.’ Existing definitions are often fairly technical, Font Vivanco explains, and they define efficiency, for example, as the ratio of the amount of fuel used compared to the amount of material transported and the distance. ‘The environmental rebound effect rests on concepts from industrial ecology and is much broader; it also takes emissions into account, for example.' 

Increase in emissions

As well as diesel cars, Font Vivanco also studied the rebound effect of electric cars, car- and bicycle-sharing systems and catalysers. 'Some innovations cannot be regarded as eco-innovations,' he concludes. 'Diesel cars even cause an increase in emissions rather than reducing them.' 

Consumers

‘Many consumers make decisions based on the information they have available and they are concerned about the environment,' says Font Vivanco. 'Our method can provide better information for people who really do want to contribute to improving the environment.'  He also believes that policy makers will benefit from these more accurate calculations. ‘If they base their policies on improvements in efficiency, they also have to recognise that this will bring about changes in demand and consumption. This improved method can help make them more aware of these effects.' 

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