HomeLow carbon futureRetrofitting buses is a fast route to greener public transport

Retrofitting buses is a fast route to greener public transport

This post is by Lucy Parkin, director of ESG at Kleanbus.

Last week’s Clean Air Day was the UK’s largest campaign to bring together communities, businesses, schools and the health sector around the impact of air pollution on all of our lives. This year’s theme recognised the impact of air pollution on every single organ in our bodies. The weight of medical evidence makes a compelling case for urgently tackling air pollution to protect health.

Transport is a major source of air pollution and, as part of the solution, we are witnessing an unprecedented shift to zero emission electric transport. The government has committed to ending the sale of new non-zero emission cars by 2030. The electric car market is growing rapidly and some months have seen new registrations of electric cars overtake those of diesel and petrol. With the average age of a car on the road in UK now under nine years, it is entirely plausible that, by 2050, every car on the road will be zero emission.

It’s imperative that public transport also keeps pace with this rapid electrification. Without it there is a risk of increasing congestion, as well as social and health inequalities. Buses are a vital transport resource which keep places moving, servicing the most disadvantaged, school children and the elderly, many of whom are also the most vulnerable to the impacts of air pollution. Switching to electric helps to eliminate diesel bus emissions from the streets and can reduce CO2 emissions by up to 80 per cent across the whole lifecycle of a vehicle.

Diesel buses could be around for a very long time
As part of the government’s plan to decarbonise transport, it recently consulted on ending the sale of non-zero emission buses between 2025 and 2032. But the diesel buses on our roads today were built to last and are expected to operate for at least 15 to 20 years. So, in 2050, it is entirely possible that there will still be diesel buses driving around our towns and cities.

The government has committed to funding 4,000 zero emission buses, around ten per cent of the UK’s fleet, but so far it has only allocated funds for 2,000 in England and a further 600 in the rest of the UK. As new electric buses cost around 50 per cent more than their diesel counterparts, compounded by long lead times and slow fleet turnover rates, the road to a fully zero emission bus fleet could be long and costly. The challenge is not restricted to the UK; over 97 per cent of the world’s three million buses are diesel.

Given the urgent needs to reduce CO2 in the atmosphere and improve air quality for health, the government, local authorities and operators must find a way to honour their environmental commitments and speed up the way to a fully electric fleet.

Refitting existing buses is cheaper and faster
Which brings us to repowering. In short, at Kleanbus we take the polluting diesel engine out and replace it with a state of the art zero emission electric powertrain, in a fraction of the time and at a fifth of the cost of buying a new electric bus.

For the government and local authorities, this allows them to reach their targets sooner, saving significant amounts of both money and emissions. For operators, the benefits are numerous. Repowering reduces operating costs immediately, extends the life and value of the existing fleet and addresses the problem of old diesel buses being deployed to the more socially deprived areas. To add to the long list of benefits, repowering an existing bus can prevent the considerable environmental impact of manufacturing new electric buses, which can be as much as 40-80 per cent of their total lifecycle carbon footprint.

The engineering challenge isn’t simple, with the large variety of bus makes and models, and operational requirements. But the benefits are so great that we are determined to offer this solution to bus owners and operators far and wide.

Electrification of bus depots is also complex, but this challenge is rapidly being overcome by energy and charging infrastructure companies. Repowering legacy diesel vehicles could be a cost effective solution, enabling operators to capitalise on the long term operational savings of depot electrification.

Funding models need updating
But to do it well, the funding structure needs updating. The government recently announced that the Bus Service Operator Grant, (BSOG), which previously favoured the operation of diesel buses, will now put zero emission buses on an even footing. Fortunately, this includes repowered buses. An accreditation scheme is being worked up to ensure that those that qualify have to meet the highest levels of performance.

The bus industry, and its customers, need proof of performance, and the increasing number of repowered bus trials, funded via the government’s Air Quality Grant by forward thinking local authorities, will help provide this assurance. Further funding from the government for repowering would also help to speed up the process.

While it isn’t the whole answer, repowering can sit alongside new zero emission buses to provide cleaner air, quieter places and lower carbon emissions much sooner.


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Green Alliance is a charity and independent think tank focused on ambitious leadership and increased political support for environmental solutions in the UK. This blog provides space for commentary and analysis around environmental politics and policy issues as they affect the UK. The views of external contributors do not necessarily represent those of Green Alliance.