Materials

Materials

Lower-clinker cements

Cement emissions

Problem

Ordinary cement is a major source of global CO₂.

Fix

Lower-clinker cements (e.g. calcined clay & limestone blends) cut emissions at scale.

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Materials

Mass timber and CLT

Steel-and-concrete mid-rises

Problem

Mid-rise buildings usually mean steel and concrete, both carbon-heavy to make. Wood was long limited to small houses by fire codes.

Fix

Cross-laminated timber and related mass-timber panels are already used in mid-rise buildings in Europe, Canada, and a growing U.S. market: including projects such as Brock Commons in Vancouver and Nordic offices. Carbon stays stored only if the forest is not stripped and the building lasts. Fire, moisture, and honest forest sourcing are the real constraints: not a cartoon of wooden skyscrapers replacing all concrete.

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Materials

Scrap furnaces and hydrogen iron

Blast-furnace steel

Problem

Making iron in a coal-fired blast furnace is one of the largest industrial CO₂ sources. The world still needs steel for rails, machines, and frames.

Fix

Melting scrap in an electric-arc furnace is the proven lower-carbon path where scrap and clean power exist. Hydrogen-based direct reduced iron: SSAB’s HYBRIT plant in Sweden is a serious industrial trial: is beginning, not a global swap. Scrap is limited, hydrogen is scarce, and most tonnes still come from coal.

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Materials

Recycled aggregate

Virgin stone while demolition rubble is dumped

Problem

Construction and demolition debris: soil, stone, concrete, brick, ceramics: is often Ireland’s largest waste stream. Virgin quarry rock still fills roads while that rubble goes to landfill.

Fix

Ireland’s EPA published national end-of-waste criteria for recycled aggregates in 2023. Clean crushed material can leave the waste regime and be sold as a product for general fill, roads, railway ballast, and other non-structural uses. A public register lists authorised producers. The criteria do not turn every mixed demolition pile into structural concrete. Contaminants stay waste. Recycling rubble is not a license to demolish faster.

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Materials

Geopolymer and alkali-activated binders

Binders that must cook limestone

Problem

Ordinary Portland cement needs a kiln that calcines limestone. That chemistry releases CO₂ even before the fuel is burned. Demand for concrete is still measured in gigatonnes.

Fix

A 2024 perspective in the Journal of the American Ceramic Society treats geopolymers and alkali-activated materials as binders made from aluminosilicate precursors: metakaolin, fly ash, slag: reacted with alkaline (or, less often, acid) activators instead of Portland clinker. Civil engineers often use the names loosely. The authors say life-cycle results are often better than Portland cement but not always, especially when sodium silicate and heat curing dominate. Precursors such as coal fly ash and blast-furnace slag are becoming scarcer. Codes, leaching tests, and worker safety for strong alkalis still limit everyday pours. This is not a drop-in bag of ordinary cement.

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Materials

Recycled and secondary aluminium

New metal from ore when scrap already exists

Problem

Primary aluminium starts from bauxite and a power-hungry smelter. Scrap that could be remelted is still landfilled or exported as mixed waste.

Fix

The International Aluminium Institute says aluminium can be recycled repeatedly without losing its properties, and that about 75% of all aluminium ever produced is still in use. IAI figures for 2019 put primary energy at 186 GJ per tonne versus 8.3 GJ for recycled metal: about 95% less. For 2022 it reports 15.1 tonnes of CO₂e per tonne of primary metal versus 0.52 for recycled metal (gate-to-gate). Those are industry numbers. Recycling still needs collection, sorting, and a furnace. It does not make extra cans a climate strategy.

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Materials

Hemp fibre insulation and hempcrete

Insulation that starts as a fossil foam

Problem

Much building insulation is mineral wool or plastic foam. Those products work, but they start from mined or fossil feedstocks and do little with agricultural fibre.

Fix

ISO 24260:2022 specifies factory-made hemp-fibre mats and boards for building insulation: products that are more than 50% hemp fibre by mass, with or without other natural fibre and a polymer balance. Hempcrete (hemp-lime) is a related but different bio-composite: hurd plus a lime binder, used as non-structural infill, not as a substitute for a concrete frame. The ISO document is a product specification, not a carbon score. Hemp insulation still needs dry detailing and a structure that can carry the wall.

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Materials

Cement-plant CO₂ capture (CCUS)

Process CO₂ that fuel-switching cannot erase

Problem

Heidelberg Materials notes that about two thirds of a cement kiln’s direct CO₂ comes from calcining limestone. That gas is chemistry, not just the burner. Lower-clinker blends help; they do not zero the stack.

Fix

Carbon capture, transport, and storage is the company’s stated path for the rest. At Brevik, Norway, Heidelberg commissioned what it calls the world’s first industrial-scale cement CCS plant in June 2025. DREAM, at Rezzato-Mazzano in Italy, is a planned hybrid capture project (oxyfuel plus amine) selected for the EU Innovation Fund; a final investment decision still depends on Italian CCS rules, incentives, and the Ravenna storage pipeline. Capture is not an excuse to pour more concrete. DREAM is a funded project, not a running Italian plant.

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Materials

Reclaimed asphalt pavement (RAP)

Problem

Virgin aggregate and bitumen for every resurfacing

Fix

Milled road asphalt crushed and fed back into new hot-mix: reusing both stone and binder. FHWA treats RAP as ordinary pavement practice when mix design and QC are done right; not the same as recycled concrete aggregate on this shelf.

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Materials

Container glass cullet

Problem

Furnaces melting virgin batch while bottles go to landfill

Fix

Sorted crushed container glass remelted into new bottles and jars: closed-loop packaging material, not fibreglass scrap. Distinct from Waste PET bottle-to-bottle and from Ocean Cleanup plastics cards.

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Materials

Mineral wool insulation

Problem

Heat leaking through thin walls and roofs

Fix

Stone wool and glass wool batts/boards already standard in European renovation and new-build envelopes: cuts heating demand for decades. Distinct from Hemp fibre insulation and hempcrete on this shelf (bio-aggregate / hemp mat, not mineral melt fibre).

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Materials

Recycled copper

Problem

Primary copper mining for grids and motors that could take scrap

Fix

Post-consumer and fabrication scrap remelted into new copper with far less energy than ore: already a large share of supply. Distinct from Recycled and secondary aluminium and from steel scrap on the hydrogen-iron card.

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Materials

Wood fibre insulation

Problem

Building envelopes that lose heat through walls, roofs and floors

Fix

Factory-made mats and boards of wood fibre for the thermal insulation of buildings. The European standard for factory-made wood fibre insulation covers rolls, batts, felts, boards and slabs.

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Materials

Cellulose insulation

Problem

Building insulation that can be made from recovered paper

Fix

Loose-fill and spray-on insulation made from recovered paper fibre. The United States Environmental Protection Agency recommends 75 percent postconsumer paper for cellulose loose-fill and spray-on insulation, measured by the weight of the insulating core.

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Materials

Engineered bamboo

Problem

Bamboo structures that need shared test methods and a product specification

Fix

Bamboo strips bonded into boards and structural members. In October 2024 the International Organization for Standardization released the first international product specification for structural glued laminated bamboo, after test methods for engineered bamboo were published in 2022.

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Materials

Recycled gypsum

Problem

Plasterboard waste from construction and demolition that needs a route back into new boards

Fix

Waste plasterboard processed into recycled gypsum for new plasterboard. The European Union project Gypsum to Gypsum produced plasterboard with up to 30 percent recycled gypsum, and the United Kingdom Environment Agency quality protocol sets when recycled gypsum stops being waste.

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Materials

Structural steel reuse

Problem

Structural steel from demolition that is usually recycled by remelting

Fix

Steel members taken from buildings, such as beams and columns, and installed again in new structures. The Steel Construction Institute states that currently around 70 percent of steel scrap in the United Kingdom is exported for recycling.

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