Net zero: cars, lorries, buses and trains
The technology for zero emission cars, lorries, buses and trains largely exists and is improving all the time. Broadly, electricity and hydrogen are key, both of which can be generated from zero-carbon energy.
As demand increases and innovation drives forward, the cost of these technologies continues to fall. Beyond reducing carbon emissions, cutting air pollution is also a driver for the uptake of cleaner modes of transport.
Where are we now?
Emissions from transport have fallen slower than those from other sectors. As such, it is now the single largest UK source of emissions, accounting for 34% of emissions in 2019.
Transport emissions peaked in 2007, and have now fallen back to 4.6% below 1990 levels, down 3% year-on-year between 2018 and 2019. Rising passenger miles and the overwhelming prevalence of fossil fuelled vehicles are the reasons for this sector lagging behind others.
Over half of transport emissions come from cars. HGVs and vans each account for 15%, while buses and rail emit less than 5% each. International aviation and shipping are accounted for separately.
In the UK, battery electric vehicles (BEVs) will probably become the norm for passenger vehicles, particularly as the charging time shortens, the range increases and more charging points become available. Ranges for BEVs are increasing, with some vehicles able to travel 375 miles between charges.
As of June 2018 there were approximately 300,000 plug-in cars on the roads, up from just 3,500 in 2013. This number includes plug-in hybrids, but sales of these are expected to fall over time as BEV technology improves.
Currently combustion engine vehicles (diesel and petrol cars) are, on a like-for-like basis, less expensive to buy than BEVs, but that is expected to change in the mid 2020s.
Running costs of BEVs are already a lot cheaper than comparable combustion engine vehicles. Electricity is cheaper than fuel; and with fewer moving parts, BEV maintenance costs are lower.
Taking purchase and running costs into account, BEVs have similar overall costs to petrol and diesel cars in the first few years of ownership.
The Government has announced plans to end sales of new conventional petrol and diesel cars and vans by 2035, but is currently considering bringing this target forwards. The Committee on Climate Change, as well as business and green groups, advocate a 2030 target.
For true net zero emissions, cars depend on their power supply being clean at source (see briefing on net zero power). If all cars are battery electric models in 2050, one National Grid scenario shows an extra 6GW of peak electricity demand (compared with a current annual peak for UK power demand of 62.3GW).
Smart charging will help to ‘smooth’ peak demand by shifting charging times to when overall demand for electricity is lower, with market mechanisms driving this shift. Large numbers of BEVs connecting to the grid could require some local electricity networks to be upgraded, although trials have shown that the costs can be reduced using new technologies. Electric vehicles could also help to support the grid by providing electricity back when parked - this is known as ‘vehicle-to-grid’, and a number of Government-funded trials are underway.
The Nissan Leaf is the world's best selling BEV, and its European manufacturing site is in Sunderland. By 2016, one in five battery electric cars driven in Europe was built in the UK. London is already deploying electric taxis that have been manufactured in Coventry, which are now also being exported to the Netherlands.
The drive towards BEVs is global. China is in the lead, having deployed more than half a million electric vehicles in 2017. It has ambitious plans to produce two million ‘new energy’ (ie BEVs and fuel cell) vehicles by 2020, and is predicted to have 50% of the global EV market in 2025. Within Europe, Norway is the out-and-out leader: in 2017 sales of BEVs made up 21% of the total, while 46% of cars sold in 2019 were fully electric.
The UK boasts a number of electric bus manufacturers including Alexander Dennis, Optare and Wrights Group, and electric buses operate in cities across the UK. London is soon to expand its fleet of double decker electric buses. Roughly 13% of the total global municipal bus fleet was electric in 2017. Shenzhen, in China, has already electrified 100% of its bus fleet, which numbers 16,359 buses.
Whilst it is expected that smaller vehicles will be battery powered, the likely technology winner for decarbonising larger vehicles is a lot less certain. Known for its sporty electric cars, America’s Tesla has announced the imminent launch of the electric ‘Tesla Semi’, a lorry capable of a 500 mile range on a single charge. Chinese firm BYD has electric trucks already commercially available in China.
Other potential solutions include hydrogen-powered fuel cell propulsion, and electrifying some of the strategic road network.
Hydrogen can be generated through electrolysis, using an electric current (eg from renewable or nuclear energy) to split water into hydrogen and oxygen. It can also be made by steam reforming of methane, with the carbon dioxide generated being captured and stored.
The world’s first electrified road opened in Sweden in April 2018. In the UK, a feasibility study was conducted in 2015 on behalf of Highways England. The study found that road electrification was technically feasible, but there were other social barriers to uptake.
Shifting freight away from the congested road network and onto railways for longer journeys is also an option.
The British Government has announced that all diesel trains will be removed from the rail network by 2040. Around 42% of the UK’s rail network is currently electrified, with the vast majority of the rest being diesel-powered. This is relatively low compared to electrification rates in the Netherlands (76%) and Italy (71%).
Trains that run on electricity are mainly powered by nuclear power, under a deal signed with EDF. As the UK's nuclear fleet ages and retires, the carbon footprint of train travel could increase if this power is not replaced with another clean source. Trials to power trains by solar panels, for example, are already taking place.
Electrifying lines carries high upfront capital costs. The Great Western electrification scheme is estimated to cost £2.8 billion (£3.54m per mile), which is partly why the £38bn rail electrification programme announced in 2012 was abandoned by Government in July 2017.
Potentially the most likely alternative to full electrification of the rail network is to use hydrogen fuel cells to power trains. Train-manufacturer Alstom plans to introduce hydrogen trains to the UK imminently by retrofitting existing stock, and Germany recently began operating a hydrogen train service.