Chapter 5
Decarbonizing Conventional Building Materials
Concrete and Cement
Plastics and Polymer Composites
Masonry and Earth-Based Materials

© PhonlamaiPhoto / iStockPhoto


Aluminium production is highly energy intensive when produced from ores, whereas producing aluminium from scrap can reduce the energy demand by 70-90 per cent. Bringing the aluminium sector on a path to near net-zero emissions is possible through a combination of actions, most importantly switching to low-carbon (renewable) electricity, deploying near-zero-emission refining and smelting technologies, improving the sorting of scrap, designing alloys for recyclability and reducing demand through material efficiency.

Aluminium Has Wide-Ranging Applications in Buildings and Construction

The buildings and infrastructure sector uses more than a quarter of all aluminium produced.

With a market share of 25 per cent, the buildings and construction sector was the largest end-use sector for aluminium in 2020, using 21 million tons of aluminium (CRU Consulting 2022). In construction, aluminium is used for roofing and cladding (37 per cent), windows and doors (27 per cent), curtain walls (18 per cent) and other components (18 per cent) (Allwood and Cullen 2012).

Aluminium is produced using both primary mined materials and (to a lesser extent) aluminium scrap, which consists of both end-of-use and new (industrial) scrap. The volumes of industrial aluminium scrap are currently much higher than for other engineering materials, indicating the potential for substantial improvements in the material efficiency of aluminium (Cullen and Allwood 2013).

Aluminium from Primary Mined Ores Is Extremely Carbon Intensive

Switching from fossil fuels to hydrogen and near zero-emission electricity is a key priority for a low-carbon aluminium future.

In 2021, aluminium production contributed over 3 per cent of the world’s direct industrial CO2 emissions (IEA 2022c). Producing aluminium requires refining the bauxite ore into alumina and smelting it into metallic aluminium, the latter being by far the most energy-intensive step, accounting for three-quarters of the energy used (Gutowski et al. 2013). In primary aluminium smelting, electricity accounts for 81 per cent of the greenhouse gas emissions (Mission Possible Partnership and IAI 2023). Decarbonizing aluminium will require near zero-emission technologies for refining and smelting, switching from fossil fuels to near zero-emission electricity, and higher recycling rates (currently 70 per cent) (IEA 2022c).

Figure 5.9 Global aluminium production (2000-2030) and embodied energy, by source

Globally, the share of aluminium production from secondary scrap is increasing.

Source: Raabe et al. 2022.

Supplies of Aluminium Scrap Are Limited But Increasing

Even if all aluminium were recycled, this scrap would only replace less than half of current demand.

Primary bauxite ore continues to be the main raw material in aluminium production, although the share of secondary scrap is increasing (see Figure 5.9). In 2019, 34 per cent of aluminium was produced from scrap (IAI 2021). As with steel, scrap supplies are limited due to rapid growth and long lifetimes (over 20 years). Even if all end-of-life aluminium were recycled, the scrap would only replace less than half of today’s aluminium demand (demand in 2020 was twice that of 2000).

Figure 5.10 Shares of primary and recycled aluminium since 1950, and projections through 2050

By 2050, the share of scrap in aluminium production will be roughly equivalent to that of primary ore.

Source: IAI 2021.

By 2050, the share of scrap in aluminium production could equal that of primary ore (IAI 2021), even as production continues to rise (see Figure 5.10). If the demand for aluminium were reduced through material efficiency measures, it could represent an even higher share.


Decarbonizing Aluminium

Prioritise the use of secondary aluminium and increase scrap recycling


Using only scrap rather than primary ore could reduce the embodied energy of aluminium by 70 per cent (when considering the processing of scrap) to 90 per cent, a much higher savings potential than for steel or copper (Allwood et al. 2019; Raabe et al. 2022).


Advanced and machine-learning-assisted scrap sorting and separation techniques can improve the scrap quality by reducing impurities (Raabe et al. 2022).


Access to scrap will differ among regions, as developed countries have large in-use stocks, while developing countries have to build most of their stocks from primary aluminium (Liu, Bangs and Müller 2013).

Improve material efficiency and design to reduce the demand for primary bauxite ore


Material efficiency strategies can reduce the total demand for aluminium, therefore increasing the relative share that is produced from scrap.


Strategies include increasing yields in fabrication and manufacturing, increasing end-of-life recycling, improving the quality of scrap through better sorting, and improving product design (designing for better recyclability and for reduced material use while delivering the same services).

Design aluminium alloys with recycling in mind


With most aluminium being used in alloyed form, an important pathway towards circularity and lower embodied carbon is designing alloys that are more scrap-tolerant than current alloys.


For even greater impact, research and development are needed in a new generation of lean alloys that contain fewer impurities and therefore facilitate recycling (Raabe et al. 2022).

Shift aluminium production to renewable electricity sources


Low-carbon electricity sources are essential for further decarbonizing aluminium production.


Stark regional differences exist in the electricity mix used for aluminium smelting. In North and South America and Europe, shares of hydropower and other low-carbon sources exceed 75 per cent. Meanwhile, coal dominates in Asia (90 per cent) and Oceania (70 per cent) (IEA 2022c).