FROM THE RAW TO THE FINAL MATERIAL

Availability: Around 10 Mha of forests is destroyed each year, but 5.3 Mha/year was renewed between 2010 and 2020. Europe (+9%) and France (+20%) are leading reforestation worldwide. Each year, global forests (i.e., 4,060 Mha of the planet’s surface area) absorb 7.6 Gt of CO2, i.e., 1.5 times the amount emitted annually by the United States.

Recycling: Three major categories of wood waste are distinguished, which are nowadays processed by well-organized streams. Class A wood, derived from the processing of raw wood (planks, crates, pallets), ends up as shavings and then aggregate to be used as fuel. Class B wood (treated wood: panels, furniture, windows). After reprocessing, it is used in the production of particle board (furniture, construction materials) and pressed wood. Class C wood (electricity poles, railway sleepers), considered as hazardous, follows a specific recycling stream. The proportion between recycled wood and energy recovery varies depending on the type of wood and the country. In France, 57% of wood waste from building sites is recycled or processed, 22% is recovered as energy or heat. In the United States, the recycling proportion drops to 17% (wood from sites and packaging).

Availability: Clay makes up 1/3 of the earth’s crust. There are several types of clay with different degrees of purity (kaolin, stoneware, ball clay, fire clay, faience, specialty clays, etc.) for varied uses ranging from construction to cosmetics. One in two houses worldwide is made of bricks. Clay or terracotta is four times more insulating than concrete.

Recycling: Clay is 100% natural, rotproof, incombustible, and environmentally friendly. Its recycling primarily concerns the bricks and tiles from inert building site waste, such as glass or plaster. Two types of recovery are possible: recycling and reuse (roads, stabilized soil, compost), and reuse for new construction and renovation.

Availability: Overexploitation is endangering this resource, especially coastal and river sand. The difficulty of extraction differs depending on its origin: alluvial aggregates or from solid rock. The latter requires fracturing before crushing and transport, which affects its carbon footprint.

Recycling: The tensions regarding this material have provided an opportunity to develop specific recycling streams for salvaging and processing building site waste, as the aggregates can follow more or less the same processing cycle as the extraction of rock aggregates. Just over 5% of the recycled sand worldwide is used in construction.

Availability: The industrial silica family is vast: high-purity siliceous sands, quartz and flint pebbles, sandstone and quartzites and ultra-pure quartz, etc. Their nature and degree of purity determine their use.

Recycling: Glass is one of the very first materials in the inert building site waste recovery and processing stream. Flat glass production can contain a high proportion of cullet, recycled glass. In spring 2022, Saint-Gobain achieved a world first: manufacturing flat glass with 100% cullet. The silica used in foundry operations is largely recycled.

Availability: Sedimentary rock formed by the accumulation of algae’s internal skeletons, its global reserves are estimated to be 1 Gt. Its use in cement does not require prior calcination, which reduces its carbon footprint and cost (-30%).

Recycling: Around 17% of the diatomaceous earth used in filtration is recycled worldwide (500,000 to 600,000 t of filter cakes are produced each year in Europe – 1 t of diatomaceous earth generates 3 t of filter cakes). These recycled filter cakes are used for crop dusting, in industry, or cement production.

Availability: There are more than 1 Tt of gypsum reserves on the planet. The EU leads the list of producing countries (almost 26 Mt in 2022), followed by the United States (21 Mt), and Iran (16 Mt).

Recycling: The gypsum used in construction is 100% recyclable. Gypsum partially dehydrated at a low temperature (-200°C) becomes plaster. The process is reversible; once rehydrated, plaster becomes gypsum.
Recycling manufacturing and plasterboard installation scrap (3% in the United States, more than 5% in Japan and France) is supplemented by recycling building site waste.

Availability: The Earth has 85 Gt of iron ore. However, scrap metal recovery represents an important raw material supply. 630 Mt of it was consumed in 2022 from end-of-life vehicles, end-of-life consumer goods (electrical goods, packaging, etc.), building demolition, etc., along with 1/3 from new manufacturing scrap. In Newport (United Kingdom), the Australian recycling plant Sims Metal Management processes 450 vehicles an hour to give 350 t of metal.

Recycling: Steel is 100% recyclable thanks to the recovery of scrap metal and industrial scrap (up to 30%). Around 200 billion steel packaging items, 68% recycled, i.e., 7.2 Mt/year, are used worldwide. The global steel industry recycles 600 Mt/year of steel on average. Since the beginning of steel manufacture, recycling has reached 25 Gt worldwide.

Availability: Mainly extracted from bauxite – 380 Mt in 2022 – aluminum is the most abundant metal element in the earth’s crust after silicon, and the second most-used metal after iron (planetary reserves: 31 Gt). Its extraction in its alumina form is more economical (140 Mt in 2022).

Recycling: There is a reserve of aluminum in secondary form (recycled) from manufacturing scrap and derived from items such as cars (the automotive industry recycles 95% of the aluminum that it uses), packaging, electrical equipment, and buildings (8%). This secondary aluminum has a much lower carbon footprint; 95% of the energy required for its production is saved. Between 1886 and 2018, out of a total aluminum production of 1.4 Gt, 1.07 Gt is still in use, 34% of which in the building sector. 75% of the aluminum produced worldwide has the potential to be recycled.

Availability: For millennia, bamboo, hemp, cotton, and flax – renewable materials with a more or less low carbon impact – have covered or made up buildings. Bamboo (32 to 37 Mha worldwide, 20 to 45 t/ha produced each year) absorbs 30% more CO2 than wood. Worldwide, plant fibers take up around 70 Mha, an extremely important carbon sink and material reserve.

Recycling: Depending on its chemical treatment, bamboo is recyclable with recovery streams concerning particle board, biomass for the supply of energy or composts. Flax and cotton recycling, mainly from textiles, is largely useful for making insulation.

Availability: Sheep’s wool (2% of the textile market) is appreciated for its thermal qualities and for being fully renewable. More than 1 billion sheep are raised on earth.

Recycling: The streams mainly created by the textile industry for the most part still remain to be developed in the construction sector.