Storing carbon in trees and products key to climate change response
27 March 2019
The case for using trees to offset fossil carbon dioxide has been that they will buy us time. That still is relevant today and more so if New Zealand invests in a transition to a circular bioeconomy says Scion CEO Dr Julian Elder in response to the Farms, forests and fossil fuels report released yesterday.
“Now is the time to be having the serious conversation about a new economy and build a national consensus on how our country can grow its way to a sustainable, bio-resourced future.
“Forests, as part of a suite of tools, will always play a key role in removing carbon dioxide from the atmosphere. They are something that we can get on with while we as a nation decide how to best reduce fossil emissions through developing technologies and substitution options to reduce emissions.
“Forests store carbon for the life of the tree and thus are only part of the solution, yet harvested forests continue to help reduce greenhouse gas emissions through the life of wood products like buildings and furniture,” he says.
Using sustainable wood in construction contributes to climate change mitigation. The manufacturing and processing emissions for wood are lower than those of concrete, bricks and steel − responsible for between eight and 15 per cent of greenhouse gas emissions worldwide. Wooden materials extend carbon storage from the forest to the building – for decades, or even centuries – while replanted trees continue the carbon sequestration process.
Innovative engineered wood products, such as cross laminated timber, allows bigger and taller wooden buildings to be constructed and store more carbon. It is calculated that one cubic metre of cross-laminated timber stores 730 kilograms of carbon.
It is important for the ‘built environment’ to balance its greenhouse gas emissions. A Scion study showed that Auckland Council could achieve their emissions reduction target 25 per cent faster than planned by applying ‘urban equilibrium’ principals (where timber buildings act like carbon pools) to their forecast growth.
Using massive timber technologies, such as in large and tall buildings going up around the world, would provide other benefits too. For example, substituting building materials would reduce manufacturing emissions by 38 to 65 per cent, and prefabrication would reduce construction emissions by up to 13 per cent.
Other emissions savings would be made at end-of-life by landfilling the timber waste or using it as a substitute for fossil fuels to generate energy. Scion research shows that if New Zealand swaps just 30 per cent of our petroleum-based liquid fuel for cleaner, greener biofuel made from renewable feedstocks like fast growing trees, we would reduce greenhouse gas emissions to the equivalent of taking half the cars off the road. On the East Coast alone this would involve planting one and a half times more trees and investing $1 billion into infrastructure, creating 1,000 new jobs.