Through the blogging I’ve done for the past 11 weeks or so, I introduced several types of pollution that is commonly associated with cities. I emphasised on the importance of placing focus on cities, as these are the places where humans congregate, and anthropogenic activities are centered. We looked at case studies across different cities, and learnt about different methods in which cities use to reduce pollution and become more sustainable. Although many of the case studies I covered portrayed a relatively bleak situation, we should not be too desolate about the future, looking at the amount of innovative solutions and promising legislative changes.
As the semester closes, I would like to comment that this blog post assignment was definitely an enjoyable and fulfilling one. I hope that readers were able to learn as much as myself from reading these blog posts, and that I was able to raise awareness of the pollutive impacts happening across cities around the world, and introduce several mechanisms, policies and interesting technology that will greatly benefit the environment in terms of the environmental pollution aspect.
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.
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
Basel Convention, Cities’ Collective Solution to Transboundary Waste
Following the previous blog post on Guiyu, we learnt of the existence of the Basel Convention, which was introduced as an international agreement to ban transboundary shipment of e-waste. For this post, we delve deeper into the functions of the agreement, and critically evaluate its effectiveness.
The Basal Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal opened for signatures in 1989, and came into force three years later in 1992. It is a multilateral agreement negotiated under the United Nations Environment Program (UNEP), calling for environmentally sound management of exported and imported waste, especially in developing countries. As of November 2020, there are 187 parties to the convention. Parties under the convention are not allowed to export or import any substances that are marked as hazardous under the convention, until the receiving nation agrees to importing the waste. Hence, Basel does not enforce a ban but rather regulates the transshipment of hazardous waste.
Although a good start to tackling waste pollution, the Basel Convention is still unable to fully curb the issue of illegal dumping. Firstly, the Basel Convention is a voluntary international treaty. This means cities get to choose whether they wish to abide by the laws of the treaty. This thus poses the issue of the efficiency of the treaty; what if large waste exporters choose not to sign? Alas, this indeed happened with America, who signed the Convention but has yet to ratify it. This means that America has not made internal legislative changes to reflect the conditions of the treaty, and can technically still export hazardous waste overseas with or without proper consent.
Another flaw of the Basel Convention is the lack of enforcing tools and proper monitoring systems. As the treaty relies heavily on the communication of permits between the importing and exporting country, any lapses in the treaty is dealt with by these two nations. This makes accountability an issue, as wealthier countries have greater means of avoiding penalties. Dispute between countries can be brought up to the International Court of Justice, but oftentimes the cases are dismissed due to lack of environmental cases to base judgement off, as well as again lack of enforcing power.
Albeit the apparent shortcomings of the Basel Convention, it is still a notable attempt by the world to come together and tackle transboundary pollution. This treaty will enhance communication and the exchange of information, and kickstart the journey of accounting for each city’s toxic waste.
References
Hackett, D. P. (1990). Assessment of the basel convention on the control of transboundary movements of hazardous wastes and their disposal. American University Journal of International Law and Policy, 5(2), 291-324.
How often do you change your phones? With popular mobile companies such as Apple and Samsung releasing new phone models annually, it is very tempting for users to make the switch, often being swayed by FOMO (fear of missing out). In-fact, an average lifespan of a mobile phone is set at around five years, as this will be the period where older models no longer are able to support new software updates. Following human’s current lifestyles of heavy reliance on electronics and home appliances, it is no surprise that the generation of e-waste has seen sharp increases over the decades. Similar to municipal waste, e-waste has to be treated specially; they contain rare metals which are worth extracting before being dumped. For this blog post, we take a look at the global e-waste trade, and see how wealthier cities exploit the services of poorer cities by offshoring their e-waste on to them. We specifically look at the Chinese city of Guiyu.
Sources of E-waste
Fig 1: Guiyu is located near the coastline, making it a convenient location for receiving e-waste from ships (Source: Wang et al., 2020)
Guiyu is located in the Guangdong province, near the Southeastern coast of China. Its location near the sea allows for easier transhipment of e-waste from overseas. For over 30 years, Guiyu has specialised in informal e-waste recycling, and has become the main pillar of economy and income for the city (Wang et al., 2020). Sources of e-waste come from both within and outside the country. Domestic contribution of e-waste is quite substantial, reaching 10.1 million tonnes annually, even overtaking that of the United States (Arora & Farge, 2020). This is most likely due to rapid urbanisation and growth in the Chinese tech industry.
Still, the bulk of e-waste source comes from overseas, specifically richer western countries who have been offshoring their waste since the 1970s. Around 70% of global e-waste ends up on Chinese land, many of which are illegally dumped (Powell, 2013). This was because China offers cheaper labour and more lax environmental standards, and thus richer cities save more through shipping their waste to another city.
Impacts
Fig 2: A photograph of a young child playing amongst wires in Guiyu. E-waste has become an integral part of the citizens of Guiyu, and this has resulted in an array of implications (Source: Anna, 2009)
As Guiyu becomes overwhelmed with handling the entire world’s e-waste, health and environmental implications manifested within the citizens and lands of Guiyu. E-waste contains an array of toxic substances; persistent organic compounds can cause reproductive implications and are a form of carcinogens; dioxins can lead to neurological implications, and heavy metals can store itself in the fatty tissues of animals, bioaccumulating and causing trans-generational implications (Li & Achal, 2020). With over 80% of Guiyu’s population working in the e-waste industry, the Guiyu citizens have the highest reported levels of lead and dioxins found in people globally (Siu, 2015). These substances also leach into surrounding soil and water, and without prompt treatment and management, they can flow into the natural resources in which the citizens utilise.
Moving Forward
With its domestic e-waste issue being the worst globally, the Chinese government could not turn a blind eye, and implemented legislations banning the imports of e-waste from other countries. However, perhaps due to inexperience with handling such bans, countries are still able to find loopholes and illegal transhipment of e-waste still occurs. Aside from local legislations, international agreements such as the Basel Convention also aid in curbing the global issue of waste trade.
Li, W., & Achal, V. (2020). Environmental and health impacts due to e-waste disposal in China – A review. Science of The Total Environment, 737, 139745. https://doi.org/10.1016/j.scitotenv.2020.139745
Wang, K., Qian, J., & Liu, L. (2020). Understanding Environmental Pollutions of Informal E-Waste Clustering in Global South via Multi-Scalar Regulatory Frameworks: A Case Study of Guiyu Town, China. International Journal of Environmental Research and Public Health, 17(8), 2802. https://doi.org/10.3390/ijerph17082802
Food waste is one of the biggest waste streams in Singapore and the amount of food waste generated has grown by around 20% over the last 10 years. In 2019, Singapore generated around 744 million kg of food waste. That is equivalent to 2 bowls of rice per person per day (Towards Zero Waste, n.d.). With minimising food waste and increasing the volume of homegrown produce set as a main objective in the Singapore Green Plan 2030, the Tampines Town Council has launched a precinct-wide sustainability project in hopes of transforming Tampines into an Eco-Town.
The main feature of the Sustainability @ Tampines Park programme is taking in food waste and turning them into compost and fertiliser for vegetables and crops. The circular ecosystem starts with residents donating their food scraps to multiple food collection points across the neighbourhood. Upon collection, these food scraps will be brought to a black soldier fly facility, where the flies will break down the food materials to form compost. Black soldier fly larvae were chosen over earthworms as they decompose at a faster rate, more than 70% that of earthworms.
After decomposition, what is leftover is termed as frass, or the poop, exoskeleton and leftover food from the larvae. The frass will be used as the main source of fertiliser for the vertical high-tech farms built flanking several HDB buildings. The vertical structure is an ingenious means of utilising vertical space in our land-scare city. Leafy vegetables such as chinese spinach and nai bai the common vegetables planted. The residents even attempted to grow rice, which became a huge success following the harvest of the first batch of Temasek rice in February this year.
Readers might worry about the consequences of the flies become pests in the neighbourhood, but the Tampines plan have this covered as well. Before the larvae can morph into pesky flies, they will be fed to an on-suite tilapia farm. It has been proven that black soldier fly larvae is extremely nutritious, rich in lipids and proteins (Lopes et al., 2022), perfect for rearing plump tilapias.
Such sustainable initiatives are clear signs of residents and the city working together to tackle pollution issues such as food waste, as well as push for more green and sustainable movements.
Lopes, I. G., Yong, J. W., & Lalander, C. (2022). Frass derived from black soldier fly larvae treatment of biodegradable wastes. A critical review and future perspectives. Waste Management, 142, 65–76. https://doi.org/10.1016/j.wasman.2022.02.007
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
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.
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
Following the trend of rising population and increase in consumption, waste generation has also increased massively around the world. It is predicted that by 2050, worldwide municipal solid waste generation will hit 3.4 billion tonnes, that is 300kg worth of trash per person in a year (Statista, 2018)! With huge volumes of waste being generated yearly, cities are faced with the issue of having enough resources to collect and dispose of the municipal waste generated within its boundaries. To understand more about how cities minimise waste pollution, we take a look at the general process of waste management in a city.
Collection
Fig 1: Waste that is not properly disposed of or collected often make its way to water bodies, following the direction of storm water flow of the city’s drain system (Source: Doug’s Rubbish)
Waste management begins from collection. This means accounting for all trash created within the vicinty of the city. States with a good collection system is more likely to have lower risk of waste pollution, as most of the city’s waste is accounted for and collected to be thrown away at a proper facility. In cities from the global south, where urbanisation and city expansion far exceeds the city’s ability to plan for a comprehensive waste collection system, most municipal waste end up on the streets, and some leak into surrounding rivers or left in a plot of land with no proper facilities. This leads to pollution of the environment, and bring about negative impacts to the people around it, such as contamination of groundwater, as well as exposure to pathogens and diseases originating from the landfill, carried by pests.
Disposal
Fig 2: Untreated municipal waste is choke full of biological waste that harbour disease-causing pathogens, which can spread to humans through pests and contamination of water (Source: wikimedia commons)
Proper collection of waste is not the end of the journey for proper waste management. As previously mentioned, municipal waste is a threat to the environment as well as humans due to the sheer amount of toxic and dangerous substances it harbours. Thus, municipal waste will need to be properly treated before being sent the waste to a proper disposal facility. Incineration is a common method used in most city’s waste management system, whereby the waste is brought to an incineration plant to be combusted. Combustion not only treats the waste, it can also reduce the volume of waste by up to 90% (Demirbas, 2010). Treatment of waste for some cities however, is seen as a form of luxury; not all cities can afford to send their trash in for treatment. When untreated waste enters landfills, it threatens the environment and people near its vicinity. Subsequent blog posts will mention the dangers of poorly managed landfills.
Focus on recycling to reduce waste
As we look through the journey of waste in a city, how it goes from households all the way down to the landfills where they remain for thousands of years, one startling questions comes to mind: What happens if we run out of land for landfills? This concern has haunted cities (especially land scarce ones), and is serious enough to be reflected in one of the 17 Sustainable Development Goals established by the UN (SDG 11) (UN, 2015). Cities must look for ways to encourage the decrease in consumption and increase in recycling, else risk living side by side with the rubbish we produce in the future.
References
Demirbas, A. (2011). Waste management, waste resource facilities and waste conversion processes. Energy Conversion and Management, 52 (2), 1280–1287. https://doi.org/10.1016/j.enconman.2010.09.025
Following previous blog posts highlighting the dire health and environmental impacts of urban noise pollution, strategies of tackling noise pollution in the city quickly became top priority of the city planners. In order to implement noise pollution strategies, the first step needed is to have sufficient data describing sources and concentration of the noise. Typical data collection method today tend to be expensive and complex, hence novel solutions that can cut back these costs are greatly welcomed by noise pollution researchers.
In recent times, researchers came up with the ingenious idea of utilising the good quality microphones built into the mobile phones most citizens carry on a daily basis. This allows researchers to not only tap in on a large pool of data collectors, it also saves immense cost in providing for additional equipment for data collecting.
However, several technical challenges are still to be considered for. Things such as unobtrusiveness and correctness of usage. Unobtrusiveness refers to how much extra effort the person tracking noise levels need to make when collecting data. This will not only affect the frequency of which the users have their microphones on and tracking, it will also affect their willingness to participate. Several users have raised the concern of mistrusting the data tracking application, fearing that their private conversations might be recorded.
As for correctness, it affects the quality of data collected. When developing the noise recording app, researchers have to consider the fact that most mobile phone’s microphones have built in noise cancelling functions to facilitate better conversations. This however is the opposite of what the data collectors want. As such, the app must be able to bypass such technology for a more accurate result. Users must also be educated on the proper ways of to record the noise level; phones must not be placed in a bag or in pockets, and the microphones should not be obstructed.
Although the use of mobile phones for tracking of noise data still poses several challenges, the potential of this method is great in terms of volume and ease of data collected.
References:
S. Santini, B. Ostermaier and R. Adelmann, “On the use of sensor nodes and mobile phones for the assessment of noise pollution levels in urban environments,” 2009 Sixth International Conference on Networked Sensing Systems (INSS), 2009, pp. 1-8, doi: 10.1109/INSS.2009.5409957.
Following the previous blog, we see how noise pollution is an insidious source of pollution that plagues bustling cities. We looked at the health impacts as well as city guidelines to mitigate such impacts, but how exactly do we attempt to muffle the sounds of a city?
Most cities with good planning stem noise pollution at the very start, during the urban planning stages. Factors such as volume of traffic, vehicle distribution and urban density, all contribute to noise exposure of citizens within the city. Such factors are also often considered for when planning out zones and functions of the city. If main roads and industrial areas are situated far away from residential areas where most people congregate and rest in during night time, then this can greatly decrease the exposure of city noise pollution to humans (Morillas et al., 2018). However, in compact cities such as Singapore, we do not have the luxury of land to distance roads and industries far away from our houses. In these situations, noise mapping and urban designs can greatly alter the amount of city noise residences receive throughout the day.
Fig 1: A noise map of a residential neighbourhood in Singapore. Sources of noise can be traced effectively to better inform planners on plausible sites to implement noise control tools (Source: Garg, Lim & Lee, 2018)
When tackling noise pollution in the city, planners usually start with using the tool of noise mapping to assess and estimate noise pollution levels throughout the city, and place them on a map to better visualise the impacts. From here on, planners can choose to place noise buffer zones that also serve other functions, such as parks, between noise source and residences. Noise barriers such as walls, or soft engineered methods such as tall shrubs are also strategically placed according to the noise map, which can predict the direction of noise and pinpoint critical locations for barriers to intercept (Morillas et al., 2018).
Fig 2: Sound barriers strategically placed over certain portions of the MRT to soften the noise of the trains passing by (source: Land Transport Guru)
The tracking of urban noise pollution and noise mapping is a relatively recent one, with methodologies still in experimental stages. However, recent studies gave promising results in accuracy of noise mapping, as well as effectiveness of mitigation methods. As technology and research progresses, we can definitely hope for a more liveable and quieter city in the near future.
References
Morillas, J. M. B., Gozalo, G. R., González, D. M., Moraga, P. A., & Vílchez-Gómez, R. (2018). Noise pollution and urban planning. Current Pollution Reports, 4(3), 208–219. https://doi.org/10.1007/s40726-018-0095-7
