Sustainable Materials: With Both Eyes Open
About this book
Sustainable Materials: With Both Eyes Open Julian Allwood and Jonathan Cullen UIT Cambridge 978-1-906860-05-9 Available free online at withbotheyesopen.com Summary based on: Use Less Group website chapter listing (uselessgroup.org); Amazon product page; Goodreads description; SustainSuccess review; Semantic Scholar entry; LinkedIn article review by Niall; Allwood & Cullen (2012) and related papers including 'Options for Achieving a 50% Cut in Industrial Carbon Emissions by 2050' (Allwood et al., Environmental Science & Technology); Julian Allwood biography at Cambridge University and UK FIRES. Julian Allwood and Jonathan Cullen's 'Sustainable Materials: With Both Eyes Open' is a landmark work in the field of industrial ecology and sustainable engineering, published in 2012 by UIT Cambridge as part of the same 'Without the Hot Air' series that includes David MacKay's celebrated 'Sustainable Energy Without the Hot Air.' True to the spirit of that series, Allwood and Cullen combine quantitative rigor with accessible prose to produce an evidence-based assessment of what it would genuinely take to make the production and use of materials compatible with a stable climate. The book is freely available online from the authors' research group website, reflecting their commitment to broad public engagement with these questions.
The book's central argument can be stated plainly: the global materials industry, and particularly the production of steel and aluminum, is responsible for a substantial and growing share of greenhouse gas emissions, and the standard approach of seeking incremental efficiency improvements in production processes — what the authors call looking with 'one eye open' — cannot deliver reductions of the scale required. Only by simultaneously addressing the demand for materials — by using less, using it more efficiently, and keeping it in use longer — can the materials system be made truly sustainable. This is what the authors mean by opening both eyes.
The book begins by establishing the scale of the challenge. Steel and aluminum together are among the most consequential materials in the modern economy, forming the structural backbone of buildings, vehicles, machinery, and infrastructure. Their production is enormously energy-intensive: steelmaking through the conventional blast furnace route requires approximately 20–25 gigajoules per tonne of steel produced, while primary aluminum production, which depends on electrolytic reduction of alumina, is even more energy-intensive at around 170 gigajoules per tonne.
Collectively, the five most significant industrial materials — steel, aluminum, cement, plastic, and paper — account for roughly 55% of industrial CO2 emissions and approximately 12% of total global emissions. With demand for these materials projected to at least double by 2050, the gap between the trajectory of emissions growth and the deep reductions required to limit global warming presents an enormous challenge. Allwood and Cullen present a detailed, data-driven map of how steel and aluminum flow through the economy.
This 'material flow analysis' traces metal from primary production through intermediate processing, fabrication, manufacturing, product use, and eventual end-of-life management. One of the book's most striking findings concerns yield losses: roughly half of all liquid aluminum produced each year never reaches a final product, being lost as scrap during casting, rolling, stamping, and machining operations. Similar, if somewhat smaller, losses occur in steel fabrication.
These losses represent a massive, largely invisible inefficiency embedded in the current industrial system — a system that has historically treated material as cheap and plentiful and has therefore had little incentive to minimize waste. The book is organized around the distinction between looking with one eye and looking with both eyes open. The 'one eye' section examines the production-side options that are already well understood: improving energy efficiency in furnaces and mills, capturing and using waste heat, developing novel process routes such as direct reduction of iron ore using hydrogen, and deploying carbon capture and storage at steel and cement plants.
Allwood and Cullen assess these options honestly and acknowledge their potential, but also their limitations. Energy efficiency improvements in primary production are already substantially realized at the frontier of industrial practice; the remaining potential is real but modest. Novel process routes face significant technical and economic barriers to deployment at scale within the timeframes required.
The 'both eyes open' section introduces and systematically evaluates a set of demand-side strategies that are far less commonly discussed. These include: designing products to use less metal by eliminating structural over-specification and using material more efficiently in cross-sections and geometries; reducing yield losses in manufacturing through better process control, near-net-shape forming, and scrap management; actively diverting manufacturing scrap back into processes where it can replace primary material; re-using metal components directly at end of life rather than recycling them back to raw material form (since re-use preserves the embodied energy of fabrication as well as smelting); extending product lifetimes through better design, maintenance, and modular upgradeability; and moderating the overall growth of demand for material-intensive goods. Each of these strategies is analyzed quantitatively, with the authors estimating the potential emissions reduction achievable if the strategy were adopted at scale.
A recurring theme is that no single strategy is sufficient; the scale of decarbonization required can only be achieved by pursuing all of these approaches simultaneously. The book is notable for its intellectual honesty about the systemic changes — in business models, in design culture, in policy frameworks, and in consumer behavior — that would be required to realize this potential. The later sections of the book extend the analysis to cement, plastics, and paper, applying the same framework of production-side and demand-side analysis to these materials.
The treatment of cement is particularly relevant for the construction industry, since concrete production is responsible for roughly 8% of global CO2 emissions and its demand is driven almost entirely by the built environment. Allwood and Cullen also engage directly with the political economy of change, examining the roles that business incentives, government policy, international trade, and individual consumer choices play in shaping material demand. They argue that policy frameworks — carbon pricing, extended producer responsibility, procurement standards — can shift incentives toward material efficiency without requiring consumers to sacrifice the material services they value.
The book concludes with a frank assessment of what individuals, businesses, and governments can each contribute, and with a call for a much more serious public and professional conversation about material consumption. For the green building sector, 'Sustainable Materials: With Both Eyes Open' is an essential reference. The construction industry is responsible for a large share of global steel, cement, and aluminum demand, and the strategies the book describes — lightweighting structural systems, extending building lifetimes, designing for disassembly and component re-use, reducing construction waste, specifying recycled content — are all directly applicable to building design and procurement.
The book's rigorous quantitative approach provides the analytical foundation for genuine, numerically grounded claims about the embodied carbon of buildings and the potential of material efficiency strategies to reduce it.