The Bridge on the River. Cry!

Olympic City Hails Steel as the New ‘Green’ Infrastructure

Fri 17 Feb 23


Perspiring workers are feverishly finishing the Olympic City’s Green Bridge, punching the last rivets and erecting deck spans as the sun bounces off more than 400 tonnes of steel.

The 460-m bridge at inner-city Kangaroo Point, costing $190 million, will be the first of several “green bridges” promised by the LNP administration in 2019 and is one of two bridges being funded entirely by the Brisbane City Council.

This bridge, expected to be completed in 2024, will carry more than 6000 pedestrians, cyclists and e-mobility riders daily by 2036, potentially reducing car trips across the Brisbane River by up to 84,000 each year.

So this, we must assume, is the ‘green’ component of a structure that has absorbed less than an egg cup of carbon in its life.

Wood Central’s Jason Ross and Jim Bowden inspected the bridge to celebrate the completion of its first deck span.

For every dry tonne of timber produced, 1.8 tonnes of carbon dioxide are taken from the atmosphere. So, if the bridge’s 400 tonnes of steel were equated to 400 tonnes of wood the intake of carbon would be around 720 tonnes.

And contrary to claims around eco-credentials, not a single panel of wood will be used in the bridge’s construction … not a single panel!

How do they get away with this? Wood Central asks. Is it a gigantic textbook example of greenwashing? Where’s the wood? Where’s the renewable? Wood is wood and steel is steel. Our gripe is the name – the Green Bridge.

Wood is rightly and convincingly termed ‘the Ultimate Renewable’, the most sustainable building material on earth.

In the latest Wood Central podcast, World Architectural Festival judge and eco-architect Mark Thomson spoke on the intrinsic benefits of timber relative to all other building materials.

We only have to scroll across the WoodSolutions website to find countless examples of wood products used in bridges all over the world – bridge decks of solid sawn timber, glulam beams, external cladding and panelling, not to mention the magnificent wooden bridges in China that have lived and survived through dynasties.

Brisbane needs to lift its game if it wants to boast a climate-positive commitment for the 2032 Olympic Games.

The wood industry puts it straight for those city policymakers who haven’t caught up with the ‘Ultimate Renewable’ message.

The world’s forests and soils store more than one trillion tonnes of carbon, twice as much carbon as is in the atmosphere. Forests have the potential to absorb about 10-20% of the total global emissions projected for the first half of the 21st century.

In the 21st century, these roles must be integrated within the emerging carbon economy. But in Australia, this is not currently the case. Timber is much more than a commodity.

Forest and wood product industries contribute to long-term carbon emissions abatement in many ways, including long-term carbon emissions abatement, capturing and storing atmospheric carbon, providing long-term storage of carbon in durable wood products, providing a renewable substitute for much more emissions-intensive building materials such as steel, aluminium and concrete, and replacing carbon-intensive fossil fuel sources like coal, oil and gas with bioenergy from wood waste, forest thinning and harvesting residues.

Wood and steel hybrid… pedestrians wanting to cross Lake Zurich can walk across the longest wooden bridge in Europe, which spans 841 m and includes steel used to add to the bridge’s stability and design as well as protecting from lightning strikes.

But when trees are manufactured into products and used in buildings, a new phase of carbon mitigation begins. Wood comprises about 50% carbon by dry weight, so the wood in a building is providing physical storage of carbon that would otherwise be emitted back into the atmosphere.

If the Green Bridge must use steel then consider the many good examples of hybrid construction – wood and steel. Pedestrians crossing Lake Zurich can walk across the longest wooden bridge in Europe, which spans 841 m.

The architects made the most of a 1991 disaster which felled huge swathes of Swiss forests to obtain wood for the project. Most of the pillars supporting the bridge came from trees knocked over by the storm, although trunks were imported from France and Germany for some of the longer sections. Steel was used to add to the bridge’s stability and design as well as protecting from lightning strikes.

The Green Bridge may pass all the codes and standards for construction and safety and has a wonderful design. But if Brisbane’s 2032 Olympics says it is contractually obliged to operate as ‘climate positive’ then why use construction materials from unrenewable sources?

Let’s call it for what it is … a steel bridge. Not a ‘green’ bridge.

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