Conserving our metal energy - Avoiding melting steel and aluminium scrap to save energy and carbon - Report findings from the first theme

Aug 29, 2026

Conserving our metal energy explores how melting used steel and aluminium scrap drives significant energy demand and carbon dioxide emissions, even though recycling is often far better than producing metal from newly mined ore. It details global scrap availability constraints, contrasts energy and emissions impacts for steel versus aluminium, and explains why high-temperature processing remains a limiting factor. The report then presents findings on reuse without melting, including reuse in construction and diversion of manufacturing scrap, estimating sizable CO2 savings and future reuse potential.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages20

Reading Time50 min

AccessFree to download

Must we melt used metal?

Steel: energy, carbon, and scrap constraints

Aluminium: complex alloy recycling and energy balance

Why recycling remains carbon intensive

Reuse without melting: opportunities, estimates, and future potential

Conserving our metal energy Avoiding melting steel and aluminium scrap to save energy and carbon Conserving our metal energy Avoiding melting steel and aluminium scrap to save energy and carbon Julian M Allwood, Jonathan M Cullen, Daniel R Cooper, Rachel L Milford, Alexandra C H Patel, Mark A Carruth and Martin McBrien Copyright © 2010 University of Cambridge First published September 2010 ISBN 978-0-903428-30-9 The authors have asserted their right under the Copyright, Designsand Patents Act 1988 to be identified as authors of this work WellMet2050 is a £1 . 5m 5–year 7–person research programme at the University of Cambridge, funded by the Engineering and Physical Science Research Council (EPSRC) of the UK government to look at all options to reduce global carbon dioxide emissions associated with steel and aluminium. The project is supported by a consortium of over 20 global companies, with whom we are developing case studies, demonstrators and analyses to reveal the emissions benefit, business opportunities and technical challenges of a raft of emissions reduction strategies. Well Met2050 is focused mainly on long-term strategies related to material efficiency, and is currently exploring four themes: • reusing metal without melting • less metal, same service • longer life and more intense use of metal assets • compression of the metals manufacturing process chain This report presents the research findings from the first theme. Low Carbon and Materials Processing Department of Engineering, University of Cambridge Trumpington Street, Cambridge CB2 1PZ, United Kingdom P: +44 (0) 1223 338181 F: +44 (0) 1223 332643 [www.well](www.wellmet2050.com)[met](www.wellmet2050.com)[2050.com](www.wellmet2050.com) Must we melt used metal? Making steel and aluminium products, even from scrap, is energy intensive and contributes significantly to global carbon dioxide emissions. Must we re-melt our scrap metal? In 2008, we scrapped around 9 million tonnes (Mt) of steel in the United Kingdom1. If we had stacked it to the height shown in the picture, it would cover Hyde Park in London. Instead, we collected it in well-hidden scrap yards, and most of it was recycled by melting in electric arc furnaces . Hyde Park remains green and we can celebrate our impressive recycling statistic—provided we don’t think about the melting temperature of steel. UK steel production makes up 1% of annual global steel production2, which, following 10 years of rapid growth driven by demand in Asia, reached a historic peak of 1,350 Mt in 20071. Despite the high recovery rates of steel from consumer discards and manufacturing scrap, the supply of scrap steel is still constrained and cannot keep up with demand for new steel. Currently 35% of the world’s steel is made from scrap, the rest from newly mined ore1. Making liquid steel from scrap requires about one-third of the primary energy of making it from ore, and on average emits less than one-quarter of the carbon dioxide emissions3. This makes recycling a good idea, but with a melting temperature around 1500°C, steel-making from scrap is still energy and carbon intensive, and regardless of source, the liquid metal requires extensive energy intensive processing before it is ready for final use. In total, steel-making accounts for 9% of global CO2 emissions4 (related to energy and industrial processes), with just under 1% of global emissions arising directly from scrap melting. The story for aluminium scrap is similar to that of steel, but a little more complicated. Globally, we produce only 56 Mt of aluminium5 (24 times-less than steel production), but production requires around nine times as much primary energy per tonne of aluminium, as compared to steel6. Aluminium production accounts for nearly 1.5% of global CO2 emissions5. Producing liquid aluminium from scrap needs around 20 times less primary energy than from ore7 making recycling particularly attractive, althou

FAQs

Why does recycling steel and aluminium still require substantial energy and carbon?

Both processes rely on high temperatures to produce liquid metal, so recycling remains energy- and carbon-intensive even when it uses scrap rather than ore.

How do steel and aluminium differ in their energy and emissions profiles when recycled?

Making liquid steel from scrap uses about one-third of the primary energy of making from ore and emits less than one-quarter of the CO2, while aluminium recycling is attractive because producing liquid aluminium from scrap needs far less primary energy than from ore, though further processing is still required.

What alternative does the report examine if used metal must not be melted?

The report focuses on reuse without melting, noting reuse of steel in construction, diversion of manufacturing scrap, and potential technologies to reuse aluminium swarf without melting.

Aug 29, 2026

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