Grey Energy Impact of Building Material Recycling - A New Assessment Method Based on Process Chains

Abstract

The construction sector is one of the largest consumers of raw materials and energy globally, contributing significantly to greenhouse gas emissions. Recycling construction and demolition (C&D) waste is considered a key strategy for achieving sustainability and circular economy goals. However, the energy implications of recycling processes—referred to as grey energy—remain insufficiently understood. This paper presents a comprehensive research framework based on process chain analysis to assess the grey energy impact of recycled building materials. The study evaluates the energy consumption from demolition waste processing to the production of secondary construction materials and compares it with primary material production. Results indicate that recycling can lead to substantial energy savings, often exceeding 50%, though outcomes depend strongly on material quality, processing requirements, and system boundaries. This study presents a process chain-based methodology to evaluate the grey energy impact of recycling building materials. By integrating stage-wise energy accounting, functional equivalence, and statistical modeling, the research demonstrates that recycling can reduce energy consumption by 50–70% under optimal conditions. Regression and correlation analyses further validate the relationship between primary and recycled energy. Indian case studies highlight both opportunities and systemic challenges in implementing energy-efficient recycling systems.

Introduction

The document discusses the growing importance of sustainability in the construction industry, which accounts for a large share of global material use and energy consumption. With increasing environmental concerns, the study focuses on recycling construction and demolition (C&D) waste as a key strategy for reducing resource depletion and emissions. However, recycling also requires energy, known as grey or embodied energy, so its overall efficiency must be carefully evaluated.

Traditional Life Cycle Assessment (LCA) methods are widely used but often lack detailed analysis of recycling processes and inconsistent system boundaries. To address these limitations, the study proposes a process chain-based framework that provides a more detailed and accurate way to measure grey energy in recycling systems.

The methodology includes four main steps: process chain analysis (tracking all stages of recycling), reference check (ensuring recycled materials are equivalent to primary materials), grey energy accounting (calculating total energy use across all processes), and grey energy impact assessment (comparing primary and recycled materials to measure energy savings or losses).

The literature review shows a shift from basic LCA approaches toward more advanced, process-based methods that better capture recycling complexity. The proposed framework improves accuracy by including full recycling chains and real-world adjustments.

Conclusion

This research demonstrates that: 1) Recycling building materials generally reduces grey energy consumption 2) A process chain-based approach provides a more accurate assessment than traditional methods 3) Energy savings depend on: o Material quality o Processing requirements o Product specifications The study concludes that: • Recycling can significantly contribute to climate-neutral construction • However, poorly designed recycling systems may lead to higher energy use Future research should focus on: • Spatial analysis of process chains • Transportation impacts • Optimization of recycling technologies

References

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Copyright

Copyright © 2026 Jayant Janardhan Sahare. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.