The UN calls for a “revolution” to decarbonize buildings, responsible for 37% of CO2 emissions

The construction world "needs to have a spectacular reduction" in the volume of new concrete used, but the decline will be "gradual", indicates Anna Dyson, co-author of the report, in a telephone interview with AFP. , and director of the Center for Ecosystems at Yale University in the United States.

In fact, the share of concrete in global construction should be halved between 2020 and 2060 for the decarbonization of buildings to be effective, indicates the report published by the UN Environment (UNEP) in conjunction with the American University Yale and around sixty researchers and architects from around the world.

And two thirds of the remaining concrete should be “circular”, that is to say itself derived from recycling, reuse or made of low-carbon cements, if the planet wants to stop warming, adds the report.

Currently "the built environment is by far the leading emitter of greenhouse gases, responsible for at least 37% of global CO2 emissions", recalls the report.

Construction materials have not always been carbon emitters like steel, aluminum, glass, plastic or concrete are today.

Until the middle of the 20th century, they came overwhelmingly from renewable, biological or organic sources (wood, stone, or from agriculture such as straw, hemp, etc.) and above all local.

“It is only in recent decades that the majority of construction materials have come from extractive, toxic and non-renewable processes,” underlines Ms. Dyson.

Together, concrete, steel and aluminum are responsible for 23% of global emissions today, the report highlights.

"Cooperate"

The construction industry must absolutely “cooperate with the forestry sector and agriculture” to jointly manage wood and biomass resources and the materials of the future in the cities of tomorrow, advocates Ms. Dyson.

“It’s about initiating a sort of back-to-the-future revolution” to remove carbon from buildings and build “lighter”, she says: we must avoid the production of waste thanks to a circular approach to materials (reuse ) and computer-assisted planning if possible, choose biosourced materials such as wood or bamboo for example and improve the decarbonization of conventional materials that cannot be replaced.

The authors of the report insist that living plant biomass, that is to say green walls or roofs for example, "constitutes an important low-carbon material for the future of cities", with the development of nurturing urban agriculture in large metropolises.

The report, initially requested by Germany, will be presented in September in New York during the "UN climate week" bringing together business leaders and ministers from the sector.

But it will also be one of the pillars of the first international gathering planned for March 2024 in Paris where ministers responsible for construction and climate will be invited, a UN source added.

Furthermore, commitments could be made by certain countries during the COP28 international climate meeting in December around building decarbonization objectives, of the same type as those made during COP26 in Glasgow around transport, energy, steel, agriculture and hydrogen, adds the same source.

“There is no magic recipe” to decarbonize the building, “new materials must be added”, “change the construction processes”, and “it is not one or the other”, concludes Naomi Keena, of Canada's McGill University, also co-author of the report.