Reimagining the Built Environment: A Paradigm Shift Towards Sustainable Urban Development

The built environment encompasses all human-made structures where we live, work, and play, including homes, schools, hospitals, offices, historical landmarks, and city parks. This environment integrates essential infrastructure that distributes power, water, food, and facilitates the movement of people. As it expands, it increasingly impacts the environment. Transforming the built environment is crucial to a nation's response to climate change and represents one of the most challenging yet rewarding engineering tasks in the transition to net zero. To effectively tackle emissions, a systems approach is essential. This approach provides a clear understanding of the interactions among various systems like buildings, transport, and energy, helping identify effective policy levers and actions to decarbonize comprehensively. Without this holistic perspective, isolated changes in specific areas may result in unintended consequences (Ramakrishna et al., 2023).

The task of decarbonizing materials and tools used in building is daunting due to two main challenges. Firstly, the electrification of heavy construction machinery like large cranes and pile drivers is complex because these require high power outputs. Secondly, a significant issue is the large amount of carbon embodied in construction materials, particularly concrete. Concrete, the most utilized material globally after water, contributes to 5-7% of global carbon emissions (Griffiths et al., 2023; Olsson et al. 2023). Its strength, versatility, and low cost have made it indispensable, particularly in projects crucial for enhancing global living standards, such as low-cost housing. However, producing concrete involves heating limestone to 1400°C, initiating a chemical reaction that creates clinker and releases carbon dioxide (Liu et al., 2024; Stefaniuk et al., 2023). The high temperatures required to initiate the chemical reactions in concrete production could be powered by hydrogen, provided it is produced in a low-carbon manner. Notably, half of the CO2 emissions from concrete are from the chemical reaction itself, making the physical capture and storage of these gases a complex challenge. Decarbonizing concrete requires multiple steps, including new resources, designs, and machinery, and ultimately depends on zero-carbon energy and transport systems (Al-Yaseri et al., 2023; Chan and Zhang, 2023).

In the meantime, an evaluation to substitute concrete with alternative materials is conducted.  Cross-laminated lumber is robust and potentially carbon-neutral; yet, it necessitates deforestation, which adversely affects ecosystems.  This material, like others, necessitates additional invention and extensive testing to offer a viable alternative to commonly utilized and economically effective concrete (Bhandari et al., 2023; Shin et al., 2023).

One effective strategy to reduce concrete demand is by reusing existing buildings instead of demolishing them. For example, a major engineering project at Oxford's Wolfson College is repurposing an old building to extend its usefulness. Founded in the 1960s and constructed in the early 70s, the building and its surrounding estate have aged significantly. Recognizing its high emissions, the college has embarked on an ambitious retrofit as part of its goal to achieve net zero by 2030, aiming for a 75% reduction in emissions (Perrier, 2021). The project aims to replace the original single-glazed windows with ultra-thin triple glazing, anticipated to decrease the building's yearly space heating requirements by 80%. Furthermore, the antiquated gas boilers are being substituted with contemporary air-source heat pumps, which are generally effective in generating heat at low temperatures.

The takeaway from the retrofit project at Wolfson College is that achieving significant environmental improvements is entirely feasible, though it requires commitment, time, and some disruption. This project illustrates a message of hope rather than despair in facing the climate challenges of the 21st century. It shows that with the right governmental frameworks and financial support, and the expertise of engineers and technicians who can clearly communicate solutions to policymakers, substantial change is possible (Berawi et al., 2020)

Engineers globally are investigating techniques to repurpose concrete from deconstructed buildings, with the objective of integrating these materials into new residential and infrastructural projects, thereby promoting sustainable construction practices.  Widespread misunderstandings assert that recovered aggregates possess inferior strength and quality; although quality control poses difficulties, significant expenditure is necessary for recycling processes (Imjai, et al., 2023).  Dr. Kim, a structural engineer at Plymouth University, spearheads a project advocating for the increased utilization of recycled concrete aggregate, especially in swiftly growing areas.  Currently, 50% of the global population resides in urban areas, a statistic anticipated to increase to 68% by 2050, hence escalating the demand for new infrastructure in cities, particularly in Southeast Asia (Neupane et al., 2023).  Urban expansion frequently entails the substitution of low-rise structures with high-rise edifices, resulting in significant quantities of construction debris, which is generally classified as industrial waste.  This signifies a considerable missed opportunity.

Decarbonizing the built environment is a formidable issue, although it also offers a significant opportunity for transformation within our sector. This transition will facilitate the adoption of more sustainable practices, improve system efficiency, utilize technology, and generate new employment opportunities. By accepting this challenge and dedicating ourselves to swift transformation, our sustainability goals for 2050 will be optimistically achieved (Whulanza and Kusrini, 2023; Whulanza, 2023).