Buildings as a Global Carbon Sink: Timber Construction for Climate Change Mitigation

The construction industry stands at a critical crossroads in our fight against climate change. A groundbreaking study by researchers including Galina Churkina and Hans Joachim Schellnhuber proposes a revolutionary approach to transform urban construction from a climate threat into a powerful climate solution through the widespread adoption of timber buildings.

Trees: Nature’s Carbon Capture Technology

Trees offer us a technology of unparalleled perfection,” Hans Joachim Schellnhuber says, co-author of the study and Director Emeritus of the Potsdam Institute for Climate Research (PIK). “They take CO2 out of our atmosphere and smoothly transform it into oxygen for us to breathe and carbon in their trunks for us to use. There’s no safer way of storing carbon I can think of. Societies have made good use of wood for buildings for many centuries, yet now the challenge of climate stabilisation calls for a very serious upscaling. If we engineer the wood into modern building materials and smartly manage harvest and construction, we humans can build ourselves a safe home on Earth.

Unlike other engineered carbon sinks being developed, timber construction offers immediate benefits by utilising existing processes and replacing high-emission building materials like steel and concrete.

The Problem with Conventional Construction

The building sector currently accounts for approximately half of global steel demand and substantial cement production. Both materials have limited potential for further efficiency improvements, with steel efficiency maxing out at 24% and cement at 13%. Even with renewable energy adoption, emissions from these materials can never reach zero due to inherent chemical reactions in their production processes.

With global population growth and urbanisation trends, buildings constructed with conventional materials between 2020-2050 could consume up to 20% of our remaining carbon budget for keeping global warming below 2°C.

Modern Timber Construction: Engineering for Performance

Mass timber refers to engineered wood products like cross-laminated timber (CLT) and glue-laminated (glulam) beams that transform smaller wood pieces into large structural components. These innovative products address traditional limitations of wood by:

• Making mechanical performance more predictable
• Distributing strength characteristics strategically
• Allowing for fire-resistant designs that have been proven safe in buildings up to 18 stories
• Providing comparable structural capabilities to concrete and steel

Carbon Storage Potential

The research explored four scenarios for transitioning to mass timber in urban construction over 30 years (2020-2050):

• Business as usual (0.5% timber buildings)
• 10% timber adoption
• 50% timber adoption
• 90% timber adoption

In the most ambitious scenario (90%), timber buildings could store between 0.01-0.68 gigatons of carbon annually, creating a cumulative carbon sink of 2-20 gigatons over 30 years. This would increase the existing carbon pool in urban areas by 25-170%.

Remarkably, a five-story residential timber building can store up to 186 kg of carbon per square meter—more than three times the carbon density of the most carbon-rich natural forests (52 kg/m²).

Emissions Reduction Benefits

Buildings constructed with engineered timber generate significantly lower emissions than conventional materials. Mass timber has:

• Lower embodied carbon emissions than steel and concrete
• Lower material intensity (a timber structure weighs 50% less than a comparable steel/concrete structure)
• Reduced foundation requirements due to lighter weight

Even in the most ambitious scenario (90% timber), where emissions from mass timber production would account for 80% of construction emissions, the overall carbon footprint would be substantially lower than business-as-usual construction.

Sustainable Wood Supply

The research demonstrates that increased timber demand for construction could be met through various sustainable approaches:

• Redirecting wood currently used for short-term products (like fuel wood) to construction
• Utilising unexploited harvest potential through sustainable forest management (66% of analysed countries could sustainably harvest more timber)
• Increasing production from plantation forests, which currently occupy just 7% of forest area but produce 40% of harvested wood
• Incorporating fast-growing alternatives like bamboo in tropical regions

A Path Forward

For timber construction to reach its full climate mitigation potential, several steps are necessary:

• Building codes must be updated to allow taller timber structures
• The construction workforce needs retraining
• Manufacturing capacity for engineered timber products must expand
• End-of-life timber management must prioritise reuse and recycling
• Sustainable forest management practices must be strengthened
• Forest certification systems need robust enforcement

Answering the urgent call for climate action

Transitioning to timber cities represents a practical, immediate approach to carbon storage that works with humanity’s existing construction needs. By shifting from mineral-based to bio-based building materials, we can create durable carbon sinks in our cities while simultaneously reducing emissions and supporting sustainable forestry practices.

This material revolution, scaled appropriately and implemented alongside reforestation efforts, offers a powerful path for balancing material supply, material demand, and environmental imperatives—answering the urgent call for climate action.