The United Nations develops maps to decarbonize the polluting construction sector

The construction sector, the most polluting and difficult to decarbonize, must build less, use more sustainable materials and clean up traditional materials to reduce its emissions, the United Nations said on Tuesday.

The industry is responsible for 37 percent of global carbon dioxide emissions, and increasing urbanization is stimulating the construction of new buildings made of carbon-heavy materials, especially concrete and steel.

Booming urban environments – adding new buildings in an area the size of Paris every five days – are damaging the ecosystems that support life and posing serious challenges to combating climate change.

A report published by the United Nations Environment Program and the Yale Center for Ecosystems and Architecture on Tuesday called for the sector to prioritize a “circular” approach that avoids waste.

Net zero construction by 2050 is achievable if “governments put in place the right policy, incentives and regulation to transform how industry works,” said Sheila Agarwal Khan, Director of the Industry and Economy Division at UNEP.

Building less and reusing existing structures generates 50 to 75 percent fewer emissions than new construction, the report said.

She added that switching to renewable biomaterials such as wood and biomass could lead to emissions savings of up to 40 percent by 2050 in some regions.

Traditional materials that cannot be replaced – such as concrete, steel, aluminium, glass and brick – must find ways to decarbonise further, the report said.

Electrifying production, scaling up innovative technologies, and using more recycled materials will accelerate efforts to clean up these particularly carbon-intensive materials.

Concrete, aluminum and steel alone represent 23% of total global emissions.

The report recommended halving the share of concrete in global construction between 2020 and 2060 in order to effectively decarbonize this sector.

Two-thirds of the concrete must be “circular”—concrete that has been recycled, reused, or created using low-carbon cement.

The rest will be new low-emission cement.

Anna Dyson, lead author of the report and a professor at Yale University’s Schools of Architecture in the US, said the sector needed a “revolution”, including a “significant reduction” in new concrete production.

“But it will be gradual,” she told AFP.

Steel and concrete “often give only the illusion of durability, often end up in landfills and contribute to the growing climate crisis,” Agarwal Khan said.

‘Back to the future’

Until the mid-20th century, building materials were usually sourced locally and from renewable or organic sources such as stone and timber.

The buildings were designed “with climate conditions in mind,” and only in recent decades have the materials used mostly “extractive, toxic, non-renewable methods,” Dyson said.

She added that the construction industry must collaborate with the forestry and agriculture sectors to manage the timber, biomass and materials resources needed for future cities.

“It’s kind of a back-to-the-future revolution.”

Dyson added that living biomass on walls or roofs could be an important low-carbon material for cities in the future.

Naomi Kenna of Canada’s McGill University said there is no “silver bullet” to decarbonise industry.

“It’s about adding new materials” and “changing processes,” she said.

The report, which drew on contributions from researchers and architects from around the world, will be presented at a climate gathering of ministers and business leaders in New York next week.

It will also play an important role in the international meeting scheduled to be held in Paris in March 2024 that brings together government ministers responsible for construction and climate, according to a UN source.

The source added that some countries could make “breakthrough” commitments during the UN climate talks in Dubai starting in November, just as they did in the transport, energy, steel, agriculture and hydrogen sectors in 2021.