Air Pollution: Tech Solutions For Cleaner Air

Air pollution is a global issue, with 95% of the world's population breathing harmful air, according to the World Health Organization (WHO). As a result, cities are turning to smart city technologies and initiatives to reduce air pollution. Technological solutions are being developed to address both indoor and outdoor air pollution, with the most effective approaches combining regulatory, market-based, and technological solutions. Some of the most promising technologies include catalytic converters, smoke scrubbers, electrostatic precipitators, and natural solutions such as biofiltration systems and bioremediation.

Catalytic converters and smoke scrubbers

However, catalytic converters have some drawbacks. They can restrict exhaust flow, reducing fuel efficiency and vehicle performance. They also require a warm-up period, during which unrestricted air pollution is emitted. Additionally, the creation of these converters can be harmful, as they often require rare metals like platinum or palladium, which can create pollution during the refining process.

Smoke scrubbers, on the other hand, are effective tools for removing traditional and novel air pollutants, including particulate matter and gaseous releases. They are commonly used in industrial settings, such as power plants and water treatment facilities, to prevent air pollutants from harming nearby communities. There are two main types of scrubbers: wet scrubbers and dry scrubbers. Wet scrubbers use a liquid, usually water, to absorb particles or gases from the air, while dry scrubbers spray dry reagents into the flue stream to neutralize gases before they enter the atmosphere.

Like catalytic converters, scrubbers also have their limitations. For example, filters and demisters may be required to prevent the release of particulate matter or fine droplets of liquid along with gas streams from scrubbers. Additionally, scrubbers may not effectively remove certain pollutants, such as mercury, unless combined with other technologies like electrostatic precipitators.

While catalytic converters and scrubbers are important tools for reducing air pollution, it is essential to acknowledge that they are just one part of a comprehensive approach to improving air quality. Other innovations, such as smart city technologies, natural alternatives like bioremediation, and advancements in air purification technology, also play a crucial role in combating this global issue.

Electrostatic precipitators

ESPs work by applying an electric charge to particles in a gas stream, causing them to be attracted to and deposited on collection plates or other devices. The treated air then passes out of the ESP, leaving behind the captured pollutants. The collected material is removed from the collection plates through mechanical rapping or vibrating, and it is directed into a hopper for disposal or recycling. This process ensures that only clean air is released back into the environment.

There are two main types of ESPs: dry and wet electrostatic precipitators. Dry ESPs operate above the dew point of the gas stream to remove impurities from smoke and dust in dry environments. They are ideal for collecting ash or cement but may struggle with capturing submicron particles. On the other hand, wet ESPs operate with saturated airstreams that have 100% relative humidity. These are commonly used to remove liquid droplets, including oil, resin, tar, and sulfuric acid mist, from gas streams in industrial settings. They are particularly effective in handling wet or sticky particulate matter as they can be tightly sealed to prevent leakage.

ESPs offer several advantages over other air purification technologies. They do not require traditional filters and can be adjusted to fit the specific needs of pollutant conditions. Additionally, ESPs are highly energy-efficient, as they apply energy only to the particulate matter being collected, minimizing the impact on the flow of gases. However, one challenge with ESPs is the maintenance of the collection plates, which can be difficult to clean due to the close spacing of the plates.

Overall, ESPs play a crucial role in air pollution control, particularly in industrial settings. By effectively capturing and removing harmful particulate matter, ESPs help improve air quality, protect the environment, and reduce health risks associated with air pollution.

Photocatalytic coatings

These coatings can be applied to building surfaces and road materials, transforming them into active agents in the fight against air pollution. The photocatalytic pigments in these coatings can effectively break down harmful gases and pollutants such as nitrogen oxides (NOx), nitric oxide, acetaldehyde, ozone, and volatile organic compounds (VOCs). These pollutants are commonly emitted by car engines and various consumer products like paints, cleaners, adhesives, and sealants.

The self-cleaning properties of photocatalytic coatings further enhance their effectiveness. When exposed to light, the coating becomes hydrophilic, reducing surface tension and making it easier for rain or moisture to wash away dirt and pollutants. This feature not only keeps surfaces clean but also prolongs the lifespan of the coating by preventing premature weathering and chalking.

Research has demonstrated the ability of photocatalytic coatings to abate pollutants individually and in mixtures. Notably, binder-containing coatings have shown stable and efficient ozone conversions, even under varying humidity conditions. This technology has been successfully tested in real-world settings, such as lecture rooms, where it effectively reduced the concentration of pollutants like nitrogen dioxide (NO2).

Electric vehicles

EVs also have regenerative braking systems, which convert the energy from slowing down the vehicle back into electricity to recharge the battery. This innovation significantly reduces brake wear and the associated particle pollution, which is a concern with traditional disc brake systems in gasoline cars. Additionally, EVs are typically responsible for lower levels of greenhouse gas emissions over their lifetime, even when accounting for the carbon pollution generated during manufacturing and charging.

However, there are some considerations with EVs and their impact on air pollution. Firstly, the weight of EVs, due to their batteries, can lead to increased tyre wear and road dust pollution. The pollution from tyre wear is not unique to EVs, as all road vehicles, including heavy SUVs, contribute to this issue. Nevertheless, it is an area that requires further research and the development of improved tyres.

Another factor to consider is how the electricity used to charge EVs is generated. If the electricity comes from renewable sources like wind or solar power, then the environmental impact of EVs is significantly reduced. However, if the electricity is generated using fossil fuels, the carbon pollution associated with charging can be high.

Despite these considerations, EVs are still a crucial step towards improving air quality. The sooner the switch from fossil fuel engines to electric motors happens, the sooner the benefits of reduced air pollution will be realised.

Bioremediation

The process involves utilising living organisms such as plants, bacteria, and fungi to remediate air pollutants. This can be done through phytoremediation, which uses plants and their associated microbes, or phylloremediation, which specifically utilises plant leaves and their associated microbes. The aerial surfaces of plants, particularly leaves, offer a vast surface area for bioremediation, with an estimated total area of 4 x 10^8 km^2 on Earth. Phylloremediation has been observed in various plants, including azalea, yellow lupine, and poplar leaves, which have been found to reduce volatile organic compounds (VOCs) and other xenobiotic compounds.

Another form of bioremediation is biofiltration, which is currently the only biological technique available for remediating airborne pollutants. Biofiltration systems use microorganisms to break down pollutants into non-toxic substances. These microorganisms can be aerobic or anaerobic, and they often use the breakdown of pollutants as an energy source. Biofiltration is commonly used in sewage treatment plants, where wastewater is aerated to provide oxygen to bacteria that degrade organic material and pollutants.

Overall, bioremediation provides a natural and sustainable solution to air pollution, harnessing the power of living organisms to break down and neutralise toxic contaminants in the air we breathe.

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