Building materials most important for climate impact in bridge projects

A wooden bridge emits nearly half as much greenhouse gases from cradle to grave compared with a concrete bridge. Materials and maintenance account for the absolute largest part of the emissions. These are the results of a comparative life-cycle analysis done in Sweden by Tyréns and SP Trä on behalf of TräCentrum Norr, TCN.

Wooden bridge over Nätraån in Bjästa, Sweden. Photo: Kristofer Lönnå

“In today’s climate debate, there is a lot of talk about the importance of a low climate impact when it comes to the actual construction and transports. Our study shows that these play a significantly smaller role than the climate impact from materials and maintenance. And wood is the winner by a large margin in terms of these aspects,” says Peter Jacobsson, Development Manager at Martinsons Byggsystem, who contributed to the LCA study together with Moelven Töreboda, which are both a part of Swedish Wood’s Wooden Bridge group.

A wooden bridge emits 79 tonnes of fossil CO2 equivalents during its lifetime compared with a concrete bridge that emits 127 tonnes.

“The Swedish Transport Administration builds just over 150 road bridges every year. In addition to this, there are bridges built of other materials and those built by municipalities and private actors. The bridge projects entail a considerable climatic impact so this is important knowledge for all industry stakeholders,” says Johan Fröbel, Advisor, Wood and Glulam Products at Swedish Wood.  

The comparative study is based on an existing road bridge made of concrete on road 1759, Malmövägen over the stretch of railway Åstorp-Kattorp in Åstorp Municipality in the south of Sweden. The concrete bridge recently received an entirely new concrete superstructure on the existing concrete base.

In the study, data was gathered for a superstructure made of wood with performance characteristics equivalent to the existing bridge situation. The LCA calculations encompass the superstructure, meaning concrete and wood slab with pavement, railing and other components, and included materials and specified amounts. The study’s calculations comprise the entire life-cycle from cradle to grave, meaning the extraction of the raw materials until the bridge is in place and maintenance for the 80 years, which is both bridges’ service life. 

“This independent report is an important tool in our and the industry’s work,” says Johan Åhlén, CEO of Moelven Töreboda. He continues:

“It is also important to remember that wood building is very much a generation issue. For the younger people in the industry, wood is a given material and I am convinced that this will lead to even greater breakthroughs for wood in the future.”

Key results

  • The wooden bridge emits around 60 per cent of the amount of carbon dioxide, CO2, that the concrete bridge emits from cradle to grave.
  • The wooden bridge’s consumption of fossil energy is around 80 per cent of that of the concrete bridge.
  • For the wooden bridge’s superstructure, it is the steel materials used in the railing that have a large proportion of the environmental impact.

Supplemental facts

  • Wood is not an infinite resource, but rather is constantly renewed.
  • In the wooden bridge, 38 tonnes of glulam and 1 tonne of other wood products are used. This is material that stores carbon dioxide during its entire lifetime.
  • The wooden bridge can relatively simply be disassembled and the wood can then be combusted and replace fossil fuel.

Emissions of fossil CO2 equivalents vary from project to project and generalisations cannot be made by saying the difference is always exactly as in this study. However, the results are a clear indication of wood’s advantages in terms of climate impact.

More information
Johan Fröbel, Advisor, Wood and Glulam Products
Swedish Wood
+46-8-762 79 68

Peter Jacobsson, Development Manager
+46-910 733 171

Johan Åhlén, CEO
Moelven Töreboda
+46-506-481 89

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