SummaryMany of us enjoy outdoor BBQs, where the charcoal and wood give that characteristic smoky flavour to the food. But can you imagine what it would be like to have a BBQ inside a garden shed? The smoke and noxious chemicals would make our eyes water and cause coughing fits. For the 3 billion people relying on burning solid fuels like coal and wood for cooking and heating, this is the shocking reality. In 2016, indoor air pollution from solid fuels caused 3.8 million premature deaths worldwide. Although governments and the WHO are promoting cleaner fuels, it will take years for solid fuel to be phased out. Through SAFE (Safe Air For Everyone), we aim to build a cheap and DIY-friendly air filtration unit and air quality sensor. We plan to use readily-accessible computer fans, 3D printing, biofiltration, and particulate sensors to create a device that can monitor indoor pollution levels and respond by active and passive filtration.
The problemAccording to the World Health Organization (WHO), 91% of the world’s population is living in places where air quality does not meet WHO guidelines [1], with direct consequences to their health. A study published last April in the Journal of the Royal Society of Medicine estimates about 6, 000 Britons who have never smoked die of lung cancer every year, making lung cancer in never-smokers the seventh most prevalent cancer in the world [2]. In Mongolia, where temperatures get as low as -25ºC, there has been a rise in breathing-related diseases. According to a BBC News report [3], a big contributor to this pollution is the burning of raw coal for indoor heating. As a consequence of this type of exposure to outdoor air pollution, more than 4 million people die every year worldwide [1]. Although there are many potential sources of outdoor air pollution, one source is often overlooked: in a report from 2018 [4], the WHO stated that around 3 billion people use polluting sources for cooking, such as kerosene, coal, or wood, resulting in almost 4 million premature deaths from complications arising from inefficient and polluting cooking practices. In Kenya this problem is particularly striking, as more than 20, 000 people are dying each year due to polluting cooking fuels, with millions more at risk of dying early [5]. The WHO has defined strategies to reduce indoor air pollution and household fuels [6], including the improvement of stoves and ventilation systems in poor communities where alternative approaches are unavailable or are just too expensive. Indeed, according to a recent report on cooking practises in Kenya, local people still lack access to safer and cleaner cooking fuels [7]. Although the WHO promotes the use of cleaner fuels, it will take years for solid fuel to be phased out. Thus, in the meantime, cheap and simple air filtration devices can help improve indoor air quality for those who need it the most. A study found that 90% of the reduction in the integrated exposure to ambient and household PM2.5 pollution during 2005-2015 in China was attributable to reduced household solid-fuel use rather than governmental policies on emissions from power plants, industry, and transportation [8]. This emphasises the importance of reducing air pollution from inefficient fuel combustion. Our project, Safe Air For Everyone, or SAFE, can help decrease air pollution through affordable DIY air filters placed at the source of the pollution - indoor stoves and fireplaces - so that families can breathe more safely.
Biological systemsThe main biological component this system will utilise is low-cost activated carbon filters produced from agricultural waste [9]. Using materials such as rice husk, corncob, or wheat-husk, activated carbon filters can be produced through a simple wash, dry, and salt-based activation. We believe repurposing this waste into filters will not only improve air quality, but also provide partial relief to the negative effects our agricultural waste have on the environment. We will also trial different biomaterials to act as prefilters for our filtration units, beginning with dried banana leaves. Due to the fibrous structure of plant leaves, they could behave similarly to synthetic prefilters that screen out large particles to increase the longevity of downstream fine filters. Using as many locally-sourced components as possible will make the filtration units more sustainable for the end-users.
Hardware design goalsThe overall goal for the hardware design is to have a fully inclusive set-up that can be put together and powered simply and reliably. In order to achieve this, we intend on using power-efficient PC fans (within a casing) to create the air flow necessary for the air filtration process. Next the system will utilise a series of filters ranging from biofilters to HEPA filters. Here, the goal is to use bio/activated-charcoal filters as means to remove large particles from the air such as dust, hair, etc. Once the large particles have been cleared, HEPA filters will remove fine particles >300 nm in diameter, screening out the particles that pose the most threat to our health. Furthermore, cost-effective air particulate and chemicals sensors will be incorporated before and after the filtration process to measure the effectiveness and to determine when the filters would need to be replaced. An Arduino will be used to record and display PM2.5 and PM10 readings. Finally, our first prototype will run on a wall socket, but the long-term goal is to incorporate a mechanism (e.g., a hand crank) to help locally power the device without relying on constant electricity.
Outcomes and benefitsWe hope that our air filtration unit can ultimately reduce indoor air pollution to safe limits in lower-income households, while other alternatives cannot yet be pursued. This unit can thus be included as one of the strategies defined by WHO to reduce health and environment impacts of indoor air pollution [6].
References[1] - https://www.who.int/airpollution/en/
[2] - https://doi.org/10.1177/0141076819843654
[3] - https://www.bbc.com/news/av/science-environment-47673327/mongolia-a-toxic-warning-to-the-world
[4] - https://www.who.int/en/news-room/fact-sheets/detail/household-air-pollution-and-health
[5] - https://www.kbc.co.ke/calls-grow-to-address-inefficient-and-polluting-cooking-fuels-in-kenya/
[6] - https://www.who.int/heli/risks/indoorair/en/
[7] - https://www.dalberg.com/system/files/2018-06/Dalberg_Long-form%20report_FINAL_PDF_0.pdf
[8] - https://doi.org/10.1073/pnas.1812955115
[9] - https://doi.org/10.1016/j.matpr.2017.11.576
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