Global construction emissions could double by 2050 without change: study

KATHMANDU: A new international study states that global construction‑sector carbon emissions will double by 2050 if the current use of building materials such as cement, brick and iron continues. The study warns this trajectory would jeopardise the Paris Agreement goal of limiting global warming to 1.5 degrees Celsius.

Published on October 31, coinciding with United Nations World Cities Day, the study finds that materials such as cement and iron are major drivers of construction emissions. Lead author Chaohui Li says, “In 2022, 55% of the construction industry’s carbon emissions were found to come from materials like cement, brick and iron. Of the emissions, 6% came from glass, plastic, chemical and bio‑based materials, while the remaining 37% originated from transport, services, machinery and construction‑site activities.”

The report documents a shift in emissions from developed to developing countries. In 1995, wealthy countries produced half of construction emissions, but by 2022, their emissions had stabilised while China, India and other developing nations increased their reliance on carbon‑intensive materials such as steel and cement.

Authors warn that, unless the use of high‑carbon materials is reduced immediately, the construction sector alone could consume the entire remaining carbon budget for the 1.5°C target within the next two decades. The study calls for global cooperation to expand low‑carbon materials and to redesign construction systems.

Co‑author Jürgen Kropp of Bauhaus Earth says, “The challenges and solutions in the construction sector are not uniform globally. Achieving major change requires structural transformation at the entire supply‑chain level for biological materials, which opens the way for new alternatives to carbon‑emitting materials like cement, iron and brick.” He adds that wealthy countries should lead through improved design and stricter regulation, while developing countries, where new construction is occurring rapidly, must receive financial and technological support.

The study recommends greater use of traditional and biological materials such as mud, stone, bamboo and wood. Co‑author Prajal Pradhan of the University of Groningen, Netherlands, says, “Unless locally available traditional construction technologies are used in Nepal as well, urban expansion will have a major impact on climate goals.” Pradhan adds that traditional materials in Nepal reduce carbon and contribute to local employment, aesthetics and the green economy, and urges policymakers to prioritise biological materials in urban planning, building codes and investment policies.

The report notes that Nepal is already experiencing rapid change in building practices. National census data from 2021 show that 33% of houses remain made of mud and stone, but the share of houses with reinforced cement concrete (RCC) roof slabs rose from 18% in 2011 to 30% in 2021, and 52.2% of houses now have walls of cement‑bonded brick or stone.

Hans Joachim Schellnhuber, Director General of the International Institute for Applied Systems Analysis (IIASA), says, “Humanity has cornered itself with iron and cement. If we want to fulfil the goals of the Paris Agreement, we must reinvent the materials we build our cities with. A global construction‑material revolution based on innovation and collaboration can transform this sector from a climate problem into a basis for solution.”