Chapter 3
3.1
Circular Design Tools and Strategies for Planning and Decision-Making
3.2
Upstream Design Choices Are Key to Tackling Carbon Early
3.3
Building Less by Prioritising Renovation and Use of Existing Buildings
3.4
Focusing on End-of-Use, Not End-of-Life, to Avoid Landfill
3.5
Design for Disassembly and Modular Construction
3.6
(Re-)Use of Secondary Materials
3.7
Recycling Only as a Last Resort
3.8
Circular Strategies in New Buildings to Avoid Embodied Emissions

Focusing on End-of-Use, Not End-of-Life, to Avoid Landfill

Transitioning from end-of-life to end-of-use promotes a circular economy approach.

Traditionally, end-of-life is the phase of a product’s life cycle where the end treatment or waste management occurs. It is the final phase in the linear economy of “take, make, waste.” Three potential end-of-life strategies for dealing with a building’s materials and components include landfill, selective deconstruction and recycling.

BUSINESS AS USUAL

© Maciejbledowski / envato

Avoiding Landfill and Embracing
Material Reuse

At the end-of-life of buildings, the most common waste management strategy is demolition followed by disposal of materials in a landfill. However, this results in a loss of the invested carbon accumulated over the building’s lifespan, as well as in additional carbon emissions from demolition, transport and the landfill itself (Akbarnezhad and Xiao 2017; Di Maria, Eyckmans and Van Acker 2018). Of the roughly 100 billion tons of construction, renovation and demolition waste generated annually, around 35 per cent is sent to landfill on average (Chen, Feng et al. 2022) (see Annex 1).
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Diversion and innovative management can greatly reduce waste (Iyer-Raniga and Huovila 2020). For example, much of this disposed material could instead be recuperated and recycled, turning demolition sites into material banks for new buildings. However, greater research and development into designing recyclable components needs to be supported, and building codes need to require compliance.
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A transition to a circular economy warrants transitioning from an “end-of-life” perspective to “end-of-use.” At the end-of-use stage, there is the potential to preserve (or store) the invested embodied carbon in a future housing cycle. A circular economy strives to improve resource efficiency, primarily by closing the resource loop (Haas et al. 2015). Within the building sector, this involves reducing the use of virgin raw materials at the manufacturing phase and substituting it with secondary materials that are in their second or third life cycle – and, consequently, eliminating waste at the end-of-use phase.

FUTURE CIRCULARITY

HILDA WEGES/GETTY IMAGES

Selective Deconstruction to Avoid
Embodied Emissions

Selective deconstruction involves dismantling a building rather than demolishing it.

A potentially lower-carbon approach to the end-of-use of a building is selective deconstruction, which involves dismantling the structure rather than demolishing it. Practices of re-use, repair and recycling allow for retaining the value of the building components and materials. Research indicates that selective deconstruction can offer large carbon savings over landfill. In a study in Belgium, it led to a 59 per cent decrease in greenhouse gas emissions per capita compared to landfill, whereas implementing recycling and downcycling practices alone led to a 36 per cent decrease in emissions (Di Maria, Eyckmans and Van Acker 2018).
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Similarly, a study comparing two very different housing sectors globally – in Lima, Peru and Montréal, Canada – found that avoiding waste by diverting construction, renovation and demolition materials from landfill can greatly reduce emissions. The study found that a selective deconstruction approach of re-use and recycling had the greatest decarbonisation potential compared to landfill, leading to emission reductions of 70 per cent in Lima and 63 per cent in Montréal (see Box 3.1).

Figure 3.3 Representative housing in Lima and Montréal and typical materials used,
by mass and volume, 2019

Whereas concrete dominates in Lima’s buildings, material use in Montréal is more diverse.

Source: Keena et al. 2023

Box 3.1

Lima and Montréal: Understanding the decarbonisation potential of circular end-of-use strategies

Re-use and recycling strategies can reduce emissions in residential construction by up to 70%.

Circular end-of-use strategies can reduce the life-cycle greenhouse gas emissions associated with residential buildings in Lima, Peru by 70 per cent and in Montréal, Canada by 63 per cent. These strategies could: 1) reduce the demand for virgin construction materials; 2) make secondary materials available, thereby reducing the need to produce virgin materials; and 3) increase the re-use of materials via selective deconstruction to reduce the emissions from demolition and landfill.

Building material use in Lima: a housing boom with growing reliance on imports of high-carbon materials

In Peru, 1.8 million homes are due to be built by 2030 (National Statistics and Information Technology Institute 2017). The main construction materials used for multi-family housing projects in Lima, as of 2019, are shown in Figure 3.3, with concrete being dominant (Peruvian Chamber of Construction 2020). Although many materials are manufactured locally, there is a trend towards importing high-embodied-carbon raw materials. This includes 51 per cent of steel scrap (Ministry of Foreign Trade and Tourism 2018); 100 per cent of aluminium and floated glass (Lopez 2022); and 4.7 per cent of cement (Vázquez-Row et al. 2019). Up to 82 per cent of building construction waste in Lima is dumped at informal, illegal sites (Rondinel-Oviedo 2021), with minimal recycling.

Building material use in Montréal: Rising demand for renovations and a large share of construction waste

In 2021, Statistics Canada reported that 59 per cent of homeowners in Montréal planned a home renovation. Apartments make up 58 per cent of the city’s dwellings, with buildings of less than five storeys being the most common (Statistics Canada 2017; Statistics Canada 2019). The material breakdown of Montréal’s low-rise apartments is shown in Figure 3.3 (Keena, Rondinel-Oviedo and Demaël 2022). Across Canada, construction, renovation and demolition waste represents 20-30 per cent of all solid waste (Yeheyis et al. 2013).

Figure 3.4 Carbon impacts of different end-of-use strategies in Lima and Montréal

Re-use and recycling had the greatest potential for decarbonizing housing, compared to landfill.

Note: Scenario 1 (S1) = Selective Deconstruction (Lima: 84% re-use, 15% recycle; Montréal: 77% re-use, 21% recycle), Scenario 2 (S2) = Recycling (Lima: 96% recycling, Montréal: 94% recycling), and Scenario 3 (S3) = 100% Landfill. The legend shows assumptions on the levels of re-use and recycling viability. Source: Keena et al. 2023

The potential of end-of-use strategies to reduce emissions from residential buildings

Material management strategies employed at the end-of-use phase of buildings offer opportunities for carbon savings. Based on representative housing models (see Figure 3.3), a recent study focused on three specific end-of-use strategies for Lima and Montréal: 1) selective deconstruction, dominated by re-use but also including recycling, 2) 100% recycling and 3) 100% landfill.
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The study found that selective deconstruction (re-use and recycling) had the greatest decarbonisation potential, leading to reductions in greenhouse gas emissions of 70 per cent in Lima and 63 per cent in Montréal, compared to landfill (see Figure 3.4). Meanwhile, recycling alone reduced emissions 50 per cent in Lima and 48 per cent in Montréal. This illustrates that circular end-of-use strategies of material reuse and recycling offer a much lower-carbon approach. The emission declines are due mainly to the avoidance of landfill and to the recovery of material for reuse. Re-use and recycling lead to a reduction in the primary energy and raw materials needed to process virgin materials into new materials during the manufacturing phase.

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