Transport is currently the largest source of emissions in the UK, and the bulk of this is from road vehicles. Fortunately, there are options for transitioning away from conventional petrol and diesel cars, buses, vans and lorries.

Biofuels

Biofuels are liquid fuel alternatives to petroleum and diesel, but differ in that they originate from plants or natural processes such as growing crops to convert to plant oils. They absorb greenhouse gases like CO₂ from the atmosphere, and then release the same amount when they are combusted as transport fuels. Biofuels can be mixed in with existing fuels, meaning there are few changes to existing transport infrastructure. However, there are concerns about the large areas of agricultural land that biofuels have to take up in order to produce these fuels in meaningful numbers, and potential for higher food prices and deforestation as a result.

Electric vehicles

Vehicles that run off electricity have the potential to directly replace current road transport. Provided the electricity that powers them comes from low-carbon sources such as renewables or nuclear, then vehicles are not emitting greenhouse gas emissions, and can directly replace normal cars, trucks and so on. However, the technology relies on electricity being stored in batteries, which can be expensive and can limit the range of electric cars more than their current alternatives. Electric cars are evolving quickly to overcome these barriers, and should be cost competitive with other vehicles by 2022.

Hydrogen vehicles

Hydrogen when used as fuel only creates steam, but in order to obtain pure hydrogen large amounts of electricity need to be used to separate it from water, leading to the same problem with electric vehicles of having this form of transport reliant on clean electricity. Hydrogen vehicles have not gained traction as quickly as their electric alternatives, largely because the use of electricity for creating the fuel rather than use directly comes with larger, more wide ranging costs. These include setting up hydrogen fuel creating plants and hydrogen pipelines.

Railways

Trains take up only 2% of transport emissions alone in the UK as they currently are, making them the cleanest choice of vehicle transport. The UK rail network is predominantly split between combinations of diesel engines and electric based trains. While the latter, preferably running off clean electricity, is by far the more preferable choice for reducing emissions, many major network routes do not have electrical connections for such trains yet. A large scale transformation to provide clean electricity to all lines is likely to be the way forward to reduce the sector’s emissions.

Shipping and aviation

Boat and planes however, are more problematic. For a start, international shipping and flights can cause great problems legally to climate change politicians and law makers, for whose responsibility is it for boats and planes over international waters that no one technically owns? And even for national ships and flights, the technical solutions are more difficult than for road and rail counterparts. Electric vehicles are a possibility, but the range and capabilities of batteries as they currently are isn’t sufficient for many. Hydrogen is also a possibility, and indeed hydrogen boats are now a reality, but there are still the difficulties of setting up large scale hydrogen transport infrastructure. In short, the problems of setting up these alternatives are the same as for rail and road vehicles, but amplified, and as such it may take longer to see low carbon shipping and aviation.

Reducing use and better planning

Encouraging people to travel less or more effectively can make significant changes to transport emissions in the short term. The ways this can be done are too numerous to list here, but many may be familiar. Driving less, carpooling, cars with greater efficiency, greater use of public transport, cycling and walking, improved town planning requiring less driving, video conferencing and so on are the transport’s sector equivalent of energy efficiency in the electricity sector. These measures are touted by some as the main solutions necessary, and by others as too restricting on members of the public. While these and similar measures can indeed make a great difference, it is unlikely to eradicate the majority of transport’s emissions. However, these changes can make a prolonged change to society in unexpected ways – for example, greater numbers of citizens cycling is likely to reduce obesity and related health problems.