According to a report done by the United Nations Environment Programme (UNEP), the built environment is responsible for an estimated 40% of global energy and resource use and 30% of Construction and Demolition (C&D) waste generation and energy-related greenhouse gas emissions from building material, such as concrete, aluminium and steel. These quotas are a result of the construction Industry leaning into the linear economy model where natural resources are extracted, consumed and discarded as waste at the end of their life (take-make-dispose). In the recent decades, however, there has been an increased campaign for accountability in how we exist within our environment. One such way is in transitioning from a linear economy to a circular economy model.
A circular economy (CE) follows the 3Rs approach: Reduce, Reuse and Recycle. In construction, this is aimed at waste reduction, waste management, repair, refurbishment and other good practices that can help control and prevent pollution during the whole building lifecycle. The building lifecycle stages include raw material extraction, manufacturing, project design, construction, operation and maintenance and the end of its life as we shall look into further.
Raw material extraction
The first stage of the life cycle of a building is the extraction of raw materials. Raw materials include wood, sand, stone, aluminium, iron ore, limestone, bauxite, copper, timber, petroleum, amongst others, which are naturally embedded in the earth. Some are scarce and non-renewable.
In a circular economy, policies are created to ensure primary raw materials are supplied sustainably. For example, (1) certified wood ensures that it is sourced from sustainable forests and eliminates destructive lumbering practices. (2) waste materials from extraction can be injected back into the economy as a secondary raw material especially if no harmful chemicals are present during the recycling process. (3) mining companies are held accountable with policies created to ensure proper management of exhausted mines/quarries.
Manufacturing
In this phase, raw materials are converted into construction materials such as glass, steel, cement, concrete and plastic. This phase involves a large consumption of energy in material conversion and has large amounts of waste materials and carbon emissions to match.
A solution to this is identifying sustainable building materials to add into the library of materials will go a long way towards a circular economy. One could consider the use of bamboo, green concretes, rammed earth among other sustainable alternatives. I have covered a set of diverse building materials, which can be incorporated in construction, in my previous article here. Additionally, material passports are a great tool to inject in the circular economy practise. A material passport is a document describing the materials included in the final product to facilitate their reuse and encourage use of materials that are environmentally-friendly.
Project Design
In this phase several circular economy (CE) practices can be included. (1) The use of BIM simulation to analyse the embodied energy in materials and the potential of material re-use in different types of designs early in the project. (2) Adaptation of modular construction where the building is constructed off-site reducing environmental pollution and disruption while also ensuring minimal material wastage. (3) Carrying out Environmental Impact Assessments (EIAs) and Life Cycle Assessments (LCAs) as systematic tools of analysis for projects, policies, plans and programmes to determine their impact on the environments and society to establish mitigation measures. (4) Consider re-adaptation of the existing buildings for new functions before demolition and reconstruction.
Some sustainable design strategies that are already in play include; rain-water harvesting, use of energy-efficient appliances, solar panels, natural ventilation, environmentally friendly sewerage systems among others. These solutions cater for requirements for building occupants.
Construction
The construction phase is where the structure is developed. During this stage, material specifications, suppliers and constructive technologies should be carefully selected to avoid material waste, environmental pollution and ultimate financial losses for the client. Typically, waste materials generated in this stage are mostly sent to landfills. These waste materials contaminate soil and/or water where they are dumped. On the other hand, those that are incinerated contribute massively to greenhouse gas emissions.
With this in mind, emphasis needs to be on C&D waste recycling — turning waste into a resource to foster the circular economy. For example, aggregate produced on-site can be used as filling materials for foundation pits in other construction projects nearby. The industry should also campaign for advanced recycling technologies and recycled product certification as further strategies towards a circular economy.
Operation and Maintenance
This is most probably the longest phase, with some buildings having a life span of 80–100 years. Buildings can acquire a material passport to help owners understand the quality of materials used for operations and maintenance. Tools can also be adopted to evaluate the state of the building materials during their lifespan. Carry out Environmental and Energy Audits can minimise expenses of repair and replacing with regular preventive maintenance.
End of life/ demolition
The final stage of the building’s life cycle is the demolition stage. Demolition is the process of manually or mechanically breaking down the structure after its lifespan.
In CE, the demolition plan will highlight waste management plans and the potential for reuse or recycling of existing materials. This would be ideal as compared to acquisition of new building materials. This plan should also describe the management of demolition waste that will need to be removed from site.
This overview of every construction stage can be achieved and help in the implementation of a circular economy in the construction industry.
