Transport and sustainability
Transport and sustainability

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Transport and sustainability


The UK is seeking an 80% cut in transport's CO2 emissions by 2050. This means that, allowing for behavioural factors, the fleet vehicle average test CO2 emissions will need to be around 20 g km−1.

Improving the fuel economy of petrol- and diesel-engined cars will not produce a sufficiently radical improvement. It could possibly result in a fleet average of around 70–80 grams of CO2 per kilometre, but developments based upon mineral oil fuels and gas cannot realistically get much lower. Plug-in/extended-range EVs could have the potential to move to a fleet average of around 45 grams of CO2 per kilometre, but this will depend on the carbon content of the electricity used.

This leads us towards the use of fuels with a lower carbon content than mineral oil, and here a range of choices open out. CNG and LPG do not offer sufficient improvement and are becoming sidelined. However, three fuels – biofuels, electricity and (possibly) hydrogen – could be produced from renewable or low-carbon primary sources.

In its current state, biofuel production needs to be optimized to cut CO2 emissions and also not to have indirect negative impacts. Biofuels could potentially reduce CO2 emissions to the target amount, but there is an insufficient supply of such 'first-generation' biofuels for transport needs. However, second- and third-generation biofuels offer the potential for the production of a large amount of low-carbon fuel.

Activity 11 (exploratory)

On the basis of this free course, make a list of the key issues that affect the introduction of biofuels, electric and hydrogen vehicles.

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Your list is likely to contain a variety of issues. As noted above, biofuels need to shift to second- and third-generation fuels to avoid the problems of indirect environmental and social/economic impacts, and also to ensure sufficient supply.

BEVs depend crucially on the decarbonization of both electricity production and the production of the vehicles and batteries themselves, but if this were to occur then it would represent a possible path towards a car with CO2 emissions of 20 g km−1. However, a crucial user barrier is that the purchase cost of electric (and hydrogen) vehicles is high compared to that of petrol and diesel cars.

Like BEVs, hydrogen fuel cell cars depend on fuel production decarbonization, this time of hydrogen. Hydrogen also faces problems of storage and distribution infrastructure. It may be that vehicles are not the best use of hydrogen and decarbonized electricity owing to the large losses in the fuel conversion chain. For these reasons, hydrogen cars may only be a viable path to low CO2 emissions if the technology can be incorporated into a new service system that delivers significant energy efficiency gains. Optimized service designs such as that developed by Riversimple can achieve CO2 emissions of around 30 g km−1, but a fleet average would probably be more like that for plug-in/extended-range EVs (about 45 g km−1).

Hybrid technologies could help to optimize each fuel. Indeed, biofuel plug-in/extended-range EVs could be an important development, and have the potential to out-compete both BEV and hydrogen fuel cell technologies.

A further key point emerging from this examination of more sustainable transport technologies is the need to link technological developments to behavioural factors. To achieve transport sustainability, it could be necessary to change the way we obtain and use cars and mobility. Thus not only are new technologies emerging, but new mobility business models are as well. These may involve car leasing models, such as the one being trialled by Riversimple, but might extend to more radical service models – for instance, a car/mobility club in which people are not financially locked in to the use of one car, but receive an integrated service package that allows them use of different cars depending on what kind of trip they are making, as well as providing for bus, train and bike use.

Overall, we may be on the verge of a time of experimentation and competition between transport technologies, and also a time of experimentation and competition in how mobility is provided. How all this will be resolved is unclear. Today, traditional ways of buying and using cars are deeply entrenched in our culture. This has constrained the technical approaches to cutting transport's environmental impacts. However, in the future a more systemic design approach could become possible – and may in fact be inevitable if sustainable transport is to become a reality.


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