Cleaner air on the bus could soon be a reality


Marvin Seibert is measuring the airflow on newly installed, ten meters long air extraction ducts on a 70-passenger hybrid-electric city bus. Photo: Mark Harris.

During the corona pandemic, most people who had a choice steered away from travelling by bus. We have been urged to avoid and not contribute to congestion on board. New technology for air purification in buses offers hope for safe public transport even in times of pandemic.

You might call it innovation in response to a crisis – new technology for air purification in vehicles like buses and cars. The technology uses the vehicle’s internal combustion engine as a heat source to sterilise the air and purify it from aerosols that may contain infectious agents, such as coronavirus. The technology has been in live testing since the summer of 2021, when it was installed on a fossil-free hybrid-electric bus in urban traffic – a bus that has since travelled more than 20,000 kilometres.

“When the pandemic hit, we wanted to do something to help; to use our knowledge in a way that would make a difference in society. It is hard to avoid congestion in public transport; the whole point is to have high density. So, we got the idea of simply doing something to improve the air quality and air hygiene in buses,” says Marvin Seibert, a researcher at the Department of Cell and Molecular Biology at Uppsala University.

Applying knowledge of virus aerosols

Marvin Seibert has spent over 15 years experimenting with viral aerosols, tiny virus-laden particles that people infected with viruses release just by breathing. Together with research colleagues, he has created and studied virus aerosols for basic research purposes.

Marvin Seibert. Photo: Mark Harris.

“Now we are doing the opposite! This innovation project is about killing the aerosolised infectious agents, and heat is an excellent sterilising medium,” Marvin Seibert states.

He also highlights the stark contrasts between this project and his normal research life.

“It is amazing to see that you can go from idea to reality so quickly. Normally in my research, we perform experiments with virus aerosols, take X-rays and publish our findings. Then it is over. In this project, we are working in the real world. Hopefully, we will soon be able to disseminate the solution further.”

Simple but effective solution

The technological solution can be installed on existing vehicles and uses much of what is already in it, with the internal combustion engine being the key. The engine compartment is 3D scanned and then the necessary components are designed and printed using 3D printers. Hoses run from the engine compartment through the roof of the bus to ventilation openings, and the installation is barely visible to passengers. No filters, chemicals or disinfectants are used.

“It has been a bit of a challenge for us to make sure the first installation, which is now on a bus in regular service, is both stylish enough and hidden. However, this requirement from the bus company has meant that our solution is already much closer to a finished product than a prototype,” explains Marvin Seibert, adding that the installation is entirely on the inside of the bus and does not take very long to do – a mechanic can easily handle it in a few hours.

3D printed under-pressure relief valve and ducting installed in the engine bay of the bus. A temperature logger monitors the temperature of the new parts during test drives. Photo: Mark Harris.

The results from approximately 200 days of real-world testing of the technological solution are good, and no problems or faults have been detected so far. But, according to Marvin Seibert, it is not yet possible to quantify how much the technology reduces the risk of spreading infection.

“We can show that the technology takes out the air and kills viruses effectively, but how much it reduces the risk of virus transmission on board depends on many interacting factors and would take many years and enormous resources to measure accurately. However, it is a perfectly reasonable assumption that the spread of infection is reduced by the improved air quality,” he says.

Pandemic a catalyst for entrepreneurship

To bring the technology to market, Marvin Seibert and fellow researcher Kerstin Mühlig have set up a company called Virubustor. Kerstin Mühlig currently runs the company, and the research and development work has so far been funded by Vinnova. In addition to the bus company, the KTH Royal Institute of Technology and the motorsport company PBZ are also partners in the collaboration. Although progress has been rapid from the idea stage, there are still several challenges on the journey to market, and time is an important factor. 

“Without the pandemic, no Virubustor. The idea for this solution was born out of the pandemic and will help fight it. It is therefore important to get it to market very soon. But getting from where we are today to a finished product that can be sold will cost more than it did to develop the prototype that is now being tested. What we are trying to do now is find investors to finance the development step,” says Marvin Seibert.

Exploring new markets and business models

In parallel, the team is exploring markets other than public transport buses. In February, the team will be heading north in Sweden to test the technology for ambulances in cold weather and to meet potential customers and partners. In Piteå, they will visit the Race of Champions motorsport event, an activity made possible by financial support from UU Innovation.

“We will talk to motorsport enthusiasts to see if there is an interest in the technology for private cars. The technology can be transferred to cars with internal combustion engines, including hybrids and plug-in hybrids, and we know that risk of spreading infectious agents in a car is quite high. It is the smallest space you normally share with others, such as your family,” he says.

Something else the team is taking a closer look at is the business model, where a tightly priced industry is forcing creativity in that area as well.

“One idea we are pursuing is the concept of 3D advertising. Since the air vents can be 3D printed it is easy to make them as custom designed shapes to represent clients’ products or ambient artwork. Better air for the passengers and advertising revenue for the bus companies – that would be an irresistible product,” says Marvin Seibert.

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Last modified: 2023-12-01