Carpooling is great. Taking public transportation is also great. Becoming a vegan/vegetarian? Also great! All three of these actions have the ability to decrease the abundance of air pollutants within the atmosphere. However, this is not a suitable long term solution. Net outputs of greenhouse gases will continue to rise without strict policies or ever-developing technological innovations for the long term, although this does not only mean using technology to actively track and monitor the trends in air pollution in various areas and cities but directly reducing the numbers.
Gas to Liquids
One solution to tackle emissions from diesel vehicles is to switch to alternative fuels. Whilst electric and liquified petroleum gas offer completely separate fuel systems, there are also other options which offer the potential to clean up existing diesels. For example, Shell has developed a new synthetic “gas to liquid” (GTL) fuel from natural gas which is a replacement for diesel. Testing has shown that the use of GTL in heavy duty vehicles such as trucks, buses and ships could reduce Nitrogen Oxide (NOx) emissions by 5-37%, and Particulate Matter (PM) emissions by 10-38%, depending on the vehicle age. GTL fuel is already being produced in significant quantities globally, and is available commercially in the Netherlands, but its use is currently very limited in the UK. Similarly, natural gas can also be converted into dimethyl ether (DME) – another potential alternative to diesel. It is thought that the use of DME reduces NOx emissions by around 25% (compared to a standard diesel), and virtually eliminates PM emissions.
Hydrogen Fuel Additives
Reductions in emissions can also be achieved by improving the fuel combustion cycle in existing vehicles through the use of additives. The e-zero1 technology produced by UK developer CGON does this by feeding small amounts of hydrogen into the vehicle air intake such that it creates a more efficient burn. Independent tests show that this increases fuel efficiency, whilst reducing emissions of NOx, PM, Hydrocarbons and Carbon Monoxide. The technology can be retrofitted to existing cars and vans (petrol or diesel) and is available commercially, although to date has only been sold in relatively small numbers.
One of the mega-trends in the automotive sector is the move towards autonomous vehicles or “self-driving cars”.This could fundamentally change the way that vehicles use the road network, reducing the stop-start nature of traffic A range of studies have estimated that autonomous vehicles could improve fuel efficiency by 15-40%, reducing emissions of local pollutants as well as greenhouse gases.
An alternative to cleaning up pollutants from vehicles directly could be to deploy technologies which remove pollution from the air. For example, a number of companies are developing photo-catalytic treatments which remove pollutants from the air in the presence of sunlight. These treatments can be applied to a range of surfaces, for example roofing tiles, roofing felt or even the surface or roads.
Developers are also looking at other ways of cleaning air in urban environments. A Dutch design company has developed the “Smog Free Tower” – an air purifying tower which sucks in pollution and expels clean air. The extracted pollution is, somewhat bizarrely, turned into pieces of jewellery. The first tower has been installed in Rotterdam and the designers claim that a single tower could clean 3.5 million cubic metres of air per day. They plan to roll out the smog free towers across other global cities. These are but a few examples of the many technologies out there to reduce pollution. The challenge for policymakers will be how to support new technologies from research through to commercialisation. Other technologies face policy barriers which could be removed – for example the uptake of gas-to-liquid fuels has been hampered by fuel standards, although this is changing. However, given the overwhelming contribution of existing diesel vehicles to urban air pollution, there is arguably a need for more research into retrofit technologies. The European Commission recently launched a €1.5 million research prize for diesel retrofit technologies, but given the scale of the challenge the Government could do more to support innovation in this space.
Hu, H.; Zhang, Y.; Rao, X.; Jin, Y. Impact of Technology Innovation on Air Quality—An Empirical Study on New Energy Vehicles in China. Int. J. Environ. Res. Public Health 2021, 18, 4025. https://doi.org/10.3390/ijerph18084025