Electric vehicles produce about 50% less CO2 compared to petrol or diesel vehicles under the current grid mix (King, 2008) and this will decrease to near zero as the electricity network is decarbonised. Running the entire UK car and taxi fleet on electricity would require a quantity equal to 16% of current electricity demand (Department for Transport [DfT], 2007). However, with use of smart charging, electric cars should require little or no additional electricity production capacity because cars could be set to charge when demand is low, such as during the night. Batteries may be charged in garages, allowing vehicle owners to simply swap flat batteries. Improvements in battery technology are expected in the future, and concerns about supply limits on raw materials are unfounded. In the zerocarbonbritain2030 scenario, all transport modes that can be electrified are electrified, including all private cars and trains.
Hydrogen is able to store more energy for less weight than batteries and it can be created from zero carbon electricity using electrolysis. However, this process requires twice the energy of using batteries (King, 2008). Because of this, hydrogen is limited in the zerocarbonbritain2030 scenario to several significant niche markets where large amounts of power are required or stopping to exchange batteries is difficult, including buses and some goods vehicles.
Biofuels have been the subject of considerable controversy due to doubts about their overall greenhouse gas balance and their impact on land use change and food prices. “Second generation” biofuels, made from lignocellulosic feedstock such as wood or grasses, may be less problematic because such biofuels tend to have better greenhouse gas balances and the feedstock can be grown on a wider variety of land types. We use some lignocellulosic biofuels in the zerocarbonbritain2030 scenario to power the sectors for which there is currently no alternative to liquid hydrocarbon fuels: aviation, shipping, some heavy goods vehicles and some farm machinery. 1.67 million hectares of land in Great Britain is devoted to producing the feedstock. We assume a corresponding reduction in meat consumption, so that there will be no net increase in land use.
Changes to vehicles
“Lightweighting” could offer efficiency gains of up to 10%, at a cost of £250–500 per vehicle, while low-rolling resistance tyres and improved aerodynamics could give potential efficiency savings of 2–4% each (King, 2008). The CO2 emissions produced in manufacturing during the replacement of the entire car stock in the UK would be between 90 and 150 million tonnes – roughly equivalent to a year’s worth of carbon emissions from all transport operations in the UK. It takes over a decade for the entire national car stock to be replaced and so vehicle replacement will have to begin rapidly to be complete by 2030 (King, 2008).
New business models
The transport modal shifts in zerocarbonbritain2030 are generally away from the private car.
The economics of car use are simplified by moving the upfront costs of car purchase, insurance, and taxation to a system where drivers pay for each mile driven. This would make public transport costs more easily comparable with car costs, and would show that public transport is often a more cost-effective solution. With increased use, public transport provision can improve service and decrease prices.
Pay-per-hour car clubs and pay-as-you-drive insurance has been shown to cut trips by approximately 25%. At present, vehicle purchasers want durability, reliability and fuel efficiency. Producers however simply seek increased sales. If cars were leased and priced per mile, then incentives for durability would devolve on the leasing company. If that leasing company is also the producer, then it is also able to ensure build quality and durability rather then simply request it.
In the zerocarbonbritain2030 scenario an absolute reduction in transit is required. Passenger kilometres travelled domestically decrease by 20%, spread evenly across all modes. Domestic aviation is eliminated and international aviation decreases by two thirds due to limits on biofuel supply. Some short-haul flights can be replaced with trains and ships but an absolute reduction in transit is also likely to be required.
Aviation is always a challenge for sustainability. Fiscal policy (air passenger duty) is already being implemented in this area. In zerocarbonbritain2030, aviation has been looked at in depth. The exact future mix of services will be dependent on the priorities of individuals. In this scenario it is anticipated that aviation will be around a third of current levels.
We expect the average occupancy rate of cars, vans and taxis to increase from the current 1.6 (DfT, 2009) to 2.
The modal shift towards public transport will be significant. To facilitate this behaviour change, societal changes will be required. It will also be necessary to adapt town planning to minimise distances and maximise opportunities for walking, cycling and public transport.
By combining modal shift, increased vehicle occupancy, wider technology improvements and fuel switching, we are able to provide the required services while decreasing transport energy demand by 63% from 2008 levels. The remaining energy requirement is supplied predominantly with electricity, supplemented with some hydrogen and biofuel.
Percentage of domestic passenger kilometres travelled by mode of travel today, 2007, and in the zerocarbonbritain2030 scenario. Significant reductions in the use of cars, vans and taxis are expected by 2030, with corresponding increases in the use of local transport and walking and cycling. Source: Data for current (2007) based on statistics from DfT (2008).
Department for Transport (DfT) (2007) Low Carbon Transport Innovation Strategy, May 2007, London: DfT.
DfT (2009) National Travel Survey 2008, Transport Statistics Bulletin, London: DfT.
King, J. (2008) The King Review of low-carbon cars Part II: recommendations for action, March 2008, London: HMSO.