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.
