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The cost of building a city

The cost of building a city

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When talking about urbanisation, the mental image that comes to mind would most likely be forests and greenery being replaced by concrete buildings and asphalt roads. In the midst of creation of such an urban image, the construction industry plays one of the main roles. The construction sector accounts for around 23% of global air pollution, 50% of the climatic change, 40% of drinking water pollution, and 50% of landfill wastes (Go Contractor, 2017). Every aspect of construction poses clear environmental implications. For this blog post, we place focus on the production of concrete, a vital material in building construction.

Cement and concrete

Concrete is produced mainly through the use of three main materials; the aggregate, a binder and water. Aggregates used are usually cheaper options such as gravel or sand, and binders used are cement. Due to its low cost and relatively common material components, basic concrete production utilises Portland cement, created by heating limestone with clay. As Portland concrete is a form of hydraulic cement, it only starts to solidify under the presence of water. As such, concrete can be casted into moulds to form desired shapes by mixing all three components together.

Environmental implications

Fig 1: Quarries become desolate landscapes after it has been depleted of its resources, leaving behind polluted waters that can leach into soil and surrounding aquifers. (Source: Stone World Magazine)

Through the explanation of concrete production, we can identify a few aspects in which concrete production poses environmental or pollution issues. Firstly, the extraction of aggregates and base materials for cement is hugely pollutive. Mining activities are frequently coupled with immense air, land and water pollution. The transportation of the heavy aggregates to and from the mines also contribute significantly to air pollution (Pal & Mandal, 2021). Next, we see that concrete production can be an extremely thirsty activity, requiring large amount of water during its mixing stages. Lastly, we see that cement production is a large source of carbon emissions due to its production requiring large amount of fuel for the heating process. An estimate 8% of human global carbon emissions come from cement production alone (Nature, 2021).

Greener alternatives?

With increasing pressures to cut back on carbon emissions in the recent times, green alternatives have been gaining traction. Green cement refers to any forms of cement with aims of using a carbon-negative manufacturing process. This can be done through the use of recycled cement or concrete, or even this interesting one currently being refined by a group of researchers from the University of Edinburgh, who looks to bypass the intense heating process of cement production through the use of a bacteria and urine. With better technology, we can definitely look forward to a future with greener buildings, both in and out.

References

Concrete needs to lose its colossal carbon footprint. (2021). Nature, 597(7878), 593–594. https://doi.org/10.1038/d41586-021-02612-5

Pal, S., & Mandal, I. (2021). Impacts of stone mining and crushing on environmental health in Dwarka river basin. Geocarto International, 36(4), 392–420. https://doi.org/10.1080/10106049.2019.1597390

Singapore’s One and Only Landfill

Singapore’s One and Only Landfill

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Last blog post, we looked at Delhi’s poor waste management system, and saw the health and environmental consequences that came with negligence in building a proper waste disposal facility. Mismanaged landfills are not an uncommon thing in the world, especially in the global south where population and consumption is growing at an exceptional pace, and governments are unable to catch up with the growth. However, there still exist relatively exemplary examples of a good waste management system, which we have right here in Singapore.

Waste management in Singapore today is managed by the National Environmental Agency, and strict laws and waste policies created a comprehensive and efficient waste management system, starting from collection down to disposal in a landfill. Municipal waste from households are efficiently collected through a central refuse chute system in the building. On the streets, dustbins are also a common sight. This, coupled with a hefty littering fine of up to $5000 (EPHA, 2000) ensured that the city’s waste are all collected and accounted for. From here, the solid waste are transported to one of the four waste-to-energy incineration plants in Singapore, where they will be reduced and treated before shipping off to the star of our waste management system, Pulau Semakau.

The Semakau landfill is Singapore’s one and only landfill, located about 8km off the South coast of mainland Singapore. The landfill is a combination of two islands, Pulau Semakau and Pulau Sakeng.

A 7km bund or a barrier is built to enclose a 350 hectare area of seawater, which eventually becomes the landfill. To prevent the leakage of leachate into the surrounding seawater outside of the bund, the inner bund is layered with geofabric and clay to form an impermeable layer (NEA, 2019). Waters surrounding Semakau island is so pristine that the coral nursing facilities have been set up next to it, and the intertidal areas are able to house four endangered plant species (Wild Singapore, 2005). In fact, the waters even housed 2 Neptune’s cup sponges, which were thought to be extinct due to over-harvesting in the late 1900s (NEA, 2015).

Although Semakau landfill is doing an amazing job in keeping Singapore’s waste safely tucked away, we are still faced with the imminent issue of eventually running out of space, estimated to happen in 2035. As such, aside from proper facilities, perhaps the most important factor to a sustainable waste waste management system in a city is eliminating waste and committing to a zero waste future.

References:

Environmental Public Health (Public Cleansing) Regulations—Singapore Statutes Online. Retrieved April 8, 2022, from https://sso.agc.gov.sg/SL/EPHA1987-RG3

NEA. (2015). Phase II Semakau Landfill Ready To Meet Singapore’s Waste Disposal Needs To 2035 And Beyond. https://www.nea.gov.sg/media/news/news/index/phase-ii-semakau-landfill-ready-to-meet-singapore-s-waste-disposal-needs-to-2035-and-beyond

NEA. (2019). Phase I and the Operations of Semakau Landfill. https://www.youtube.com/watch?v=RTQvjTXs0DQ

Wild Singapore. (2005). Semakau Survey 2005. http://www.wildsingapore.com/projects/survey/semakau/results.html

Rubbish “Volcanoes”

Rubbish “Volcanoes”

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Just about a week ago, the city Delhi was engulfed in thick black smoke. The origins of the smoke can be traced back to the Ghazipur landfill, standing at a massive 65 metres tall and spanning across 70 acres wide (The Print, 2020). The landfill is one of the main dumping ground for the populous capital of India, receiving 2,000 tonnes of garbage dumped into it each day.

Fig 1: The massive Ghazipur landfill in Delhi, perpetually smoking as it burns away the methane and carbon dioxide produced (source: Money Sharma/AFP)

Landfill fires are not an uncommon sight in Delhi, where landfills are often haphazardly maintained. In fact, Delhi saw a total of 16 landfill fire in the year of 2021 – more than one per month (Outlook, 2022). Landfill fires worsen the already abysmal health and environmental impacts landfills have on its surroundings. The fires produce acrid smoke that cause initial implications such as coughing and eye irritation, and with prolonged exposure, increase the likelihood of respiratory related illnesses (Swati et al., 2017). The fires also release large volume of methane and carbon dioxide, previously trapped under layers of rubbish. Both are greenhouse gases, with methane being especially potent, having 20 times the greenhouse effect than carbon dioxide (Mohajan, 2012). Fires can also potentially destroy the linings of landfills, causing toxic leachate to leak into the soil and pollute groundwater aquifers, many of which are the main source of water for the residents of Delhi.

So what was the cause of Ghazipur’s landfill fire? For now, the Indian fire department has yet to pinpoint the specific reason, but the fires are most likely triggered by either arson or the immense heat from decomposition of the rubbish. Typical Indian municipal waste contains around 50% bio-degradable organic compounds such as excretion and food waste. When buried under many layers of trash, these organic compounds are left in oxygen deprived anaerobic conditions, perfect for decomposition and generation of landfill gases. Landfill gases contain around 40% of methane and 60% of carbon dioxide. Both gases are extremely flammable, and are responsible for fuelling the perpetual landfill fires (Kashyap et al., 2016).

Moving forward, the Indian government made promises to reduce the height of the le landfill to cut down on the health and environmental issues caused. On another hand, in the recent capitalistic times where even environmental hazards can be transformed into useful resources, researchers have plans on turning the smoking landfill into a natural gas capturing site (Kashyap et al., 2016).

References:

Kashyap, R. K., Chugh, P., & Nandakumar, T. (2016). Opportunities & challenges in capturing landfill gas from an active and un-scientifically managed land fill site – a case study. Procedia Environmental Sciences, 35, 348–367. https://doi.org/10.1016/j.proenv.2016.07.015

Mohajan, H.K. (2012), Dangerous Effects of Methane Gas in Atmosphere, International Journal of Economic and Political Integration, 2(1): 3–10.

Outlook. (2022, March 29). Ghazipur fire blazing on for over 19 hours but landfill fires not new in delhi. Https://Www.Outlookindia.Com/. https://www.outlookindia.com/national/ghazipur-fire-blazing-on-for-over-19-hours-but-landfill-fires-not-new-in-delhi-news-189002

Swati, Ghosh, P., & Thakur, I. S. (2017). An integrated approach to study the risk from landfill soil of Delhi: Chemical analyses, in vitro assays and human risk assessment. Ecotoxicology and Environmental Safety, 143, 120–128. https://doi.org/10.1016/j.ecoenv.2017.05.019

The Print. (2020, December 13). Entire garbage at Ghazipur landfill site will be processed by December 2024, claims Gambhir. ThePrint. https://theprint.in/india/governance/entire-garbage-at-ghazipur-landfill-site-will-be-processed-by-december-2024-claims-gambhir/565985/

The Asian Yellow Dust – Part 2

The Asian Yellow Dust – Part 2

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In the previous blog post, I introduced the phenomenon of the Yellow Dust that brings in air pollutants from the arid regions of continental Asia, into the cities of China, Korea and Japan. I also mentioned that the composition of the particles are mainly fine or ultra-fine sand which was the result of aeolian processes and years and years of erosions of the landscape of the deserts. From this, we would think that the causes of the Yellow Dust is inherently natural. However, as with most environmental issues, anthropogenic activities have intensified the impacts of the Yellow Dust.

 

Desertification

Fig 1: Desertification in China, where land exhausted of its water and nutrients from intensive agriculture (source: Science Photo Library)

 

The dust storms that distributes the sediments of the deserts to the entire East Asia are the result of ongoing desertification. Following global warming and climate change, which exacerbates dry spells, desertification has intensified throughout the years. Placing focus on China’s arid regions, we see that the country is expected to lose almost 1 million square kilometres of humid areas to arid and semi-arid regions by 2030 (FAO, ?). Aside from climate change, local anthropogenic activities also contributes significantly to desertification. With rapid increase of the Chinese population comes over-utilisation of China’s land resources; more land cleared to build cities to house more people, intensified agriculture and livestock rearing. Such activities places immense stress on land as well as water resources, resulting in the drying up of groundwater resources, leading to desertification (FAO, ?)

 

Industrial pollutants laced with sand sediments

During recent studies on the Yellow Dust, it was discovered that sand particles from the desert was not the only form of pollutant within the Yellow Dust. Secondary particles such as mercury and cadmium has been detected amongst the pollutants, and its origins can be traced back to the industries of China (Kang & Kim, 2014).

 

Political conflicts

Needless to say, the mitigation and slowing down of desertification, as well as the Chinese industry’s issue of transboundary pollution has brought about political discussions with the affected countries in East Asia, for example setting up a Republic of Korea-China Joint Committee on Environmental Cooperation to discuss cooperative efforts to tackle air pollution (Kang & Kim, 2014).

 

References

Kang, D., & Kim, J.-E. (2014). Fine, ultrafine, and yellow dust: Emerging health problems in korea. Journal of Korean Medical Science, 29(5), 621. https://doi.org/10.3346/jkms.2014.29.5.621

Food and Agriculture Organization of the United Nations (Ed.). (1997). Drylands development and combating desertification: Bibliographic study of experiences in China. Food and Agriculture Organization of the United Nations.

The Asian Yellow Dust – Part 1

The Asian Yellow Dust – Part 1

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Fig 1: Donning a mask is a common sight in South Korea, who battles the Misemongi yearly (source: Joel’s Travel Tips)

 

Following the most recent COVID-19 pandemic, people out and about on the streets with a face mask on is no longer an unusual sight. However in East Asian countries, specifically China and Korea, masks has been a necessity way before the COVID times. The reason for this is because cities in both countries suffer from poor air quality with a surprisingly natural origin.

 

Origins of the dust

Fig 2: The pathway of the Yellow Dust, originating from the deserts in China and Mongolia (source: National Institute of Meteorological Research)

 

The Yellow Dust that blows over East Asia originates from the arid and semi-arid regions of China, where the Gobi Desert and the Loess Plateau are located (Kar & Takeuchi, 2004). The composition of the particles in the Yellow Dust are mainly sand and soil dust, eroded through aeolian processes (Chung, 1992). During the months of spring (March to May) is when the Yellow Dust occurs. This is because as the weather warms up in the Northern hemisphere, it triggers a change in atmospheric pressure and triggers strong gusty winds as well as extratropical cyclones. These strong weather systems then transports the fine dust particles from the Chinese deserts eastwards towards major Chinese cities as well as Korea and Japan (Chung, 1992).

 

Health implications

The most obvious implications of the Yellow Dust on humans will be the health implications. Similar to the haze we face here in Southeast Asia, the Yellow Dust has particulate of sizes ranging from PM10 to PM2.5, both classified as fine and ultra-fine. PM10 particles are small enough to enter the alveoli in the lungs, while PM2.5 can permeate into the blood and lymphatic system, potentially even reaching the brains and fetal organs (Kang & Kim, 2014). The particles are also irritants, and can worsen existing conditions such as asthma and eczema.

 

Economical impacts

As the dust chokes up the city, it brings about economic downfalls as well, affecting an array of services. Firstly, as the dust is opaque and causes a decrease in visibility. Through a detailed economic analysis by Kang et al. (2004), it was estimated that South Korea’s aviation industry suffered half a million dollars lost in year 2002 from flight cancellations alone. As the dust causes health implications, it can affect productivity of the workforce, and discourage people from going outdoors, affecting various retail industries. the total cost of the Yellow Dust on South Korea in 2002 is estimated to be USD 5,600 million, or USD 117 per South Korean citizen (Jeong, 2008)

 

Any Solutions?

As the origins and causes of the Yellow Dust is inherently natural, it is difficult for governments to mitigate the onslaught of this particular type of air pollution in the city. As such, cities can only adapt through means like implementing cohesive guidelines for the public and monitoring the meteorological events closely to provide quicker alerts to its citizens.

 

References

Chung, Y.-S. (1992). On the observations of yellow sand (Dust storms) in Korea. Atmospheric Environment. Part A. General Topics, 26(15), 2743–2749. https://doi.org/10.1016/0960-1686(92)90010-I

Jeong, D.-Y. (2008). Socio-economic costs from yellow dust damages in south korea. Korean Social Science Journal, 35(2), 1–29. http://journal.kci.go.kr/kssj/archive/articleView?artiId=ART001293655

Kang, D., & Kim, J.-E. (2014). Fine, ultrafine, and yellow dust: Emerging health problems in korea. Journal of Korean Medical Science, 29(5), 621. https://doi.org/10.3346/jkms.2014.29.5.621

Kang, G. G., Chu, J. M., Jeong, H. S. Han, H. J., and Yoo, N. M.(2004). An Analysis of the Damage From YYellow Dust in Northeastern Asia and Regional Cooperation Strategy for Reducing Damage. Seoul: Korea Environment Institute.

Kar, A., & Takeuchi, K. (2004). Yellow dust: An overview of research and felt needs. Journal of Arid Environments, 59(1), 167–187. https://doi.org/10.1016/j.jaridenv.2004.01.010

Effects of light pollution on Urban Black Swans

Effects of light pollution on Urban Black Swans

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As a continuation from the previous introductory post on light pollution, we look deeper into the impacts it has on bio-diversity, specifically wildlife that shares the urban space with us. As aforementioned, exposure to artificial lighting, specifically blue light, at night-time prevents the body from producing the sleep hormone melatonin. This is why it is worth once in a while to listen to mom and put your phone away before sleeping. Other lightings such as LED streetlights are also sources of blue light pollution.

Blue light pollution is known to cause sleeplessness in humans, but what about the urban wildlife? It was predicted that warmer, amber lightings with less short, blue wavelength helps in mitigating biodiversity impacts of light pollution, and cities have transitioned into adopting them. To test the validity of this prediction, animal behaviour researchers from Australia tested whether unfiltered white light (blue-rich) and filtered amber (blue-reduced) light from LED streetlights had any implications on the rest and melatonin production in black swans.

Fig 1: The cygnus astratus, or black swan, native to Australia (photo credit: google photos)

 

The swans are ideal test subjects as they are large and can be re-captured with ease. They are also diurnal, with relatively flexible sleep patterns. This meant that the black swans are relatively resilient to sleep disruption, hence the researchers predicted that if the swans are affected by the lights, then other more sensitive urban wildlife will have a greater impact. Quality of sleep of the swans were quantified using electroencephalogram (EEG) measurements and melatonin in blood levels. It is also good to note that the swans are exposed to urban lighting in a naturalistic manner, meaning the test site was constructed to be like a typical pond in the park.

The results of the study were unexpected; where the colour of the streetlights had no differing effect on the quality of sleep of the swans. The study also confirmed that the swans rested less under white night controls over dark controls, as seen from shorter rest durations (~30 mins less) and shorter REM sleep.

Fig 2: Results of light treatment affecting the sleep cycle of the swans (photo credit: Alusebrook et al. (2020))

 

There is much to take away from this. Several interesting explanations for these results were given. Firstly, it was suggested that perhaps the swans were more disrupted by amber lighting at night was the fact that unlike humans, the swans have greater visual sensitivity for light from the red and yellow spectrum, hence amber lighting for these diurnal animals might have further stimulated them at night. Melatonin levels in the swans were also non-conclusive due to the low levels detected overall, hence the study was unable to develop a conclusion linking melatonin production to colour of lighting for the swans.

Nonetheless, the results hinted that current mitigative measures of altering the colours of streetlights is not as effective as it was once predicted to be. It is therefore more advisable to turn off streetlights entirely, especially in parks, reserves, or where plenty of urban wildlife reside, to keep disruption from artificial light pollution to bio-diversity down to a minimal.

 

References

Aulsebrook, A. E., Lesku, J. A., Mulder, R. A., Goymann, W., Vyssotski, A. L., & Jones, T. M. (2020). Streetlights Disrupt Night-Time Sleep in Urban Black Swans. Frontiers in Ecology and Evolution, 8, 131. https://doi.org/10.3389/fevo.2020.00131

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