Inventors start tackling air pollution problem

Tanya Blake

Matthew S. Johnson has been breathing in toxic fumes for decades. No, he doesn't work at a particularly dangerous chemical plant – he lives in a city.

Many big cities around the world have lately been struggling to keep their air clean; just five days into 2017, London, for instance, surpassed the annual limit set out in European law which states that hourly levels of toxic nitrogen dioxide (NO2) cannot exceed 200 micrograms per cubic metre more than 18 times in a year. Overall, Britain now faces a case at the European court of justice if it doesn't comply with these required annual limits of NO2.

You can't usually see or smell bad air. It's there, and living in it day in and day out, you get used it – you have no choice. But air pollution has been linked to dementia, heart attacks and strokes. More than 50,000 people die annually from it in Britain alone. In Europe overall, this figure is 467,000 deaths a year, according to the European Environment Agency, while China has the sixth-highest death rate linked to air pollution in the world. In India, around 620,000 people die from toxic air annually.

Measures to cut toxic elements in the air, including NO2 and harmful fine particulate matter (PM2.5), are slowly coming into force. Countries are starting to reduce the number of diesel vehicles and try making industrial emissions greener - but these early efforts will take time to have an effect. So, while governments are dragging their feet, inventors around the world are taking matters into their own hands and starting to develop new technologies to help us breathe. For some it may seem like sticking a plaster rather than a real solution, but for these scientists, it's a race against time – and people's deteriorating health.

Johnson lives in Copenhagen, where standards of living are higher than in many other cities. But even there, air pollution is a problem – and being a chemist at the University of Copenhagen, Johnson is particularly acutely aware of the issue.

One day, nearly a decade ago, he says, he realised that he had grown tired of waiting for the government to deal with toxic air – and decided to do something about it. “We know everything about air pollution. People have measured it, we know the health impacts of it, but it seemed to me that nobody was really doing anything about it,” Johnson says. “This feeling of frustration led me to invent a new way of cleaning air.”

His first invention developed in 2008 was the so-called gas phased advance oxidation (GPAO) process that traps 'bad' gas molecules. Catching molecules is not an easy task, as they are tiny, few and widely spaced in the atmosphere.

GPAO works as a sort of ‘chimney’ for a factory, where the gas mixes under scrutiny with ozone, causing molecules to stick together. These sticky molecules are then passed under ultraviolet light, which makes yet more of them to cluster faster. As they grow bigger, the molecules become easier to manage and eventually turn into motes of dust, which is removed by first electrically charging it to make it stick to a surface, and then by pulling it from the air stream with an opposite charge. The system effectively ‘eats dust,’ including dangerous particles like pollen and spores. 

Sounds effective – but Johnson says that for cities his invention doesn't work as well. “It turns out that in a city like London you have a lot of diesel engines and this represents a very special pollution problem, because you have very high levels of NOx and particulate matter,” he says. 

So together with colleagues at his company Airlabs, he had to come up with a different cleaning mechanism to make urban air cleaner. His new system is based on the original GPAO technology, but rather than collecting pollution over a large industrial space it collects the NOx and particulate matter using a disposable solid state filter, dubbed PurePack.

This system can remove more than 90% of NOx and particulate matter in its surrounding area, says Johnson. It works by taking in polluted air, filtering it and pumping it out clean - using just a fan and a small amount of electricity.

At home in Denmark, they have installed such a device at the University of Copenhagen but say it would work best in crowded areas where pollution is rampant, such as cafes on busy streets and train platforms. “We found that you need to have both passive and active elements to get a good air treatment,” say Johnson. “This could be a wall or tree to block the airflow and create a pocket of clean air in the “leeward space”.

To work out the best design and location to install the clean air systems they use a combination of computational flow dynamics and hand held gas monitors. 

Clean air bench at Kings College London

The UK is also testing Johnson’s invention. At King’s College London, Airlabs has put an extra bench – but a special one. The firm calls it ‘a clean air bench’. With a high back to act as a windscreen, the bench creates what Johnson describes as a “bubble of clean air” for those sitting on it -as well as for people standing nearby.

Finally, another device has been installed in the Danish embassy in Beijing. This was done due to a unique legal quirk, Johnson says - while the building is in China, it is technically European territory and was therefore flouting the safe levels of pollution for workers set by the EU.

Apart from these systems, Johnson is also now working with South Korean tech giant Samsung to develop a domestic clean air filter that would be built into air conditioning units to improve the health of people in big cities in Asia.


A shared ambition

Johnson is not alone in his efforts to make the air cleaner. Italian architect Stefano Boeri has suggested his own solution to tackle China’s air pollution with plans to create two high-rise towers coated with 23 species of tree and more than 2,500 shrubs. The buildings, currently under construction, will contain offices, a 247-room luxury hotel and a green architecture school. Due to be complete by 2018, Boeri believes that by introducing more trees and shrubs to cities they will clean the air, absorbing CO2, producing oxygen and absorbing dust produced by urban traffic. These ginormous manmade yet natural air filters would be just the beginning: Boeri also plans to create entire forest cities in China.

On perhaps a slightly less ambitious scale is Dutch entrepreneur and inventor Daan Roosegaarde’s plan to tackle China’s smog problem. When Roosegaarde visited Beijing in 2013, severe smog prevented him from seeing anything from his hotel room window, and he found out that parents kept their children indoors to prevent possible lung damage. The experience prompted him to develop what he calls the world’s largest smog vacuum cleaner - the Smog Free Tower. His device is currently installed in the 798 Art Zone –a former industrial park that has become an established art and design district. It will soon be showcased in other Chinese cities in the hope that they apply the technology. 

The Tower works by capturing airborne pollutants and storing them in the system's collector plate. It then transforms the particles into coarse dust, immobilising them, and thus preventing them from being emitted and inhaled. Finally, pumps out the purified air from vents on its four sides.

The device can capture more than 75% of the PM2.5 and PM10 airborne smog particles, says Roosegaarde, while releasing clean air all around it, with a 360-degree coverage. In late 2016, the device worked for 41 days in Beijing and cleaned 30 million cubic metres of the Chinese capital's air - the same volume as 10 Beijing National Stadiums. It has also captured billions of harmful PM2.5 airborne particles, says Studio Roosegaarde, the inventor’s startup (right?).

Chinese officials confirm that the mechanism is having an effect - according to the the country’s government reports, the air in the vicinity of the Smog Free Tower was 55% cleaner.

Wider scale measures

Despite these efforts, not everyone is convinced that such small-scale clean air technologies are truly effective in tackling urban air quality. “Air moves quickly and so the purified air will not make a big enough impact unless people are really close to the Tower,” says Zongbo Shi, an environmentalist at Birmingham University. 

Instead, he thinks it is much more crucial to control the source of emissions. “Air purifiers in offices or homes may reduce the pollution levels, but how effective they are in improving health [is not clear],” he says.

Cities like London, Delhi and Beijing are now implementing practical measures such as ultra-low emission zones and the ban of old, polluting diesel vehicles, particularly during smog alerts. According to a recent King’s College London report, Lethal and illegal solving London’s air pollution crisis, the impact of removing diesel cars from the UK capital’s roads could be huge in improving air quality. The researchers estimate that simply cutting the number of diesel cars in inner London to 5% and increasing cleaner alternatives would bring 99.96% of London into compliance with legal levels on NO2. To do so, the team suggests a progressive “phase-out” approach of getting rid of the cars by 2025.

And the politicians are paying attention. London mayor Sadiq Khan has followed the report's tips and has increased regulation and road charging to help improve air quality as quickly as possible. He will make older, more polluting cars pay a £10 charge to drive in central London from 23 October 2017.

He also plans to extend an existing ultra-low emission zone beyond central London to the North and South Circular roads from 2019 – but banning or curbing the number of diesel cars is not yet on the horizon.

The fight for better air quality is not always very straightforward, though. In India, for instance, the Delhi Supreme Court has recently reinstated the sale of large diesel cars, mainly SUVs with an engine capacity of 2000cc or more due to pressure from the automotive industry. Despite this, manufacturers and dealers will now have to pay a 'green fine' to compensate for polluting the city's air.

While better air has clear benefits for people's health, it could also be a boon financially. A World Bank study has found that in 2013, air pollution deaths cost the global economy about US$225 billion (£184 billion) in lost labour income.

Johnson agrees that these wider measures are crucial - but feels that technology like his could also help to play a small part in making up for economic losses created by air pollution. He aims to create attractive ‘clean air zones’ in shopping districts, for example, to boost tourism.

While it may seem like small, individual efforts of developing air purifying technology can only ever create a tiny improvement to a very big problem, the Danish inventor is pragmatic about its usefulness. “We see an opportunity at least 10 years out for active air cleaning,” he says. Whatever the long-term future for his devices, he is not about to stop, and wants governments to follow suit – now. It’s about time our cities got a breath of fresh air.




Professional Engineering magazine

Current Issue: Issue 1, 2024

01 Cover_Final online

Read now

Professional Engineering app

  • Industry features and content
  • Engineering and Institution news
  • News and features exclusive to app users

Download our Professional Engineering app

Professional Engineering newsletter

A weekly round-up of the most popular and topical stories featured on our website, so you won't miss anything

Subscribe to Professional Engineering newsletter

Opt into your industry sector newsletter

Related articles