Development of a Life Cycle Assessment Allocation Approach for Circular Economy in the Built Environment

Leonora Charlotte Malabi Eberhardt,Freja Nygaard Rasmussen,Anne Van Stijn,Harpa Birgisdottir,Morten Birkved

doi:10.3390/su12229579

Leonora Charlotte Malabi Eberhardt, Freja Nygaard Rasmussen + Show 3 more

Open Access

https://doi.org/10.3390/su12229579

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Abstract

Transitioning the built environment to a circular economy (CE) is vital to achieve sustainability goals but requires metrics. Life cycle assessment (LCA) can analyse the environmental performance of CE. However, conventional LCA methods assess individual products and single life cycles whereas circular assessment requires a systems perspective as buildings, components and materials potentially have multiple use and life cycles. How should benefits and burdens be allocated between life cycles? This study compares four different LCA allocation approaches: (a) the EN 15804/15978 cut-off approach, (b) the Circular Footprint Formula (CFF), (c) the 50:50 approach, and (d) the linearly degressive (LD) approach. The environmental impacts of four ‘circular building components’ is calculated: (1) a concrete column and (2) a timber column both designed for direct reuse, (3) a recyclable roof felt and (4) a window with a reusable frame. Notable differences in impact distributions between the allocation approaches were found, thus incentivising different CE principles. The LD approach was found to be promising for open and closed-loop systems within a closed loop supply chain (such as the ones assessed here). A CE LD approach was developed to enhance the LD approach’s applicability, to closer align it with the CE concept, and to create an incentive for CE in the industry.

Highlights

The current linear economy of take–make–use–dispose has resulted in a building sector that accounts for 40% of the waste generated, 40% of material resource use and 11% of all human-induced emissions globally come from manufacturing building materials and products [1,2]
To determine which approach was most suitable for assessing circular economy (CE) within a building context, the approaches were compared on: (1) the effect they have on the Life cycle assessment (LCA) outcomes and the incentive they create for CE principles, (2) their ability to assess both the product and system perspective of CE, (3) how they address uncertainty, and (4) their practical application
Implementing multiple cycles in LCA is challenging, but designing for slowing, closing and narrowing loops could significantly reduce the waste, resource use and environmental impacts emanating from the building sector

Summary

Introduction

The current linear economy of take–make–use–dispose has resulted in a building sector that accounts for 40% of the waste generated (by volume), 40% of material resource use (by volume) and 11% of all human-induced emissions globally come from manufacturing building materials and products [1,2]. Assessing the environmental benefits of CE requires a multi-cycling systems perspective This is because CE is operationalised through value retention processes (VRPs) ( known as R-imperatives), such as, reduce, reuse, repair, refurbish, recycle and recover of which some result in re-loops [17]. Assigning environmental impacts deriving from one or more processes to more than one product systems—allocation—should be avoided by: (1) dividing the processes into sub-processes and ‘cutting off’ the sub-processes providing the secondary function, or by (2) ‘system expansion’, where the secondary functions of the initial product system are integrated into the system boundary This is done using a substitution method in which the initial process is credited with the impact that the secondary function potentially avoids by substituting the most likely corresponding technology and/or practice in the subsequent use cycle

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