Concrete is the most widely used construction material in the world. It is extremely versatile, inflammable and comes at an appealing price point.
Made by combining cement with water, sand and broken stone or gravel, the end result is a pourable substance that can be shaped or moulded before it hardens.
For all these positives though there is one glaring negative: concrete produces a lot of carbon pollution. Seriously, a lot.
One report by Chatham House estimates the four billion tonnes of cement produced each year contributes around eight per cent to the world’s CO2 emissions. That’s more than oil and gas production (6.4 per cent) and nipping at the heels of the entire transportation sector (14.3 per cent).
Another downside is its reliance on the world’s rapidly shrinking supply of sand. A number of sources have suggested we are in the early stages of a global sand shortage and it seems the demand for concrete will only get higher.
While the sector has started to innovate in the right direction (by using supplementary materials such as fly ash or waste plastics) it will take a far more substantial change to make the industry sustainable.
Steel is an infinitely recyclable material that can be used in a way that reduces the quantity of other materials needed to create sturdy structures.
It is made by heating iron to molten liquid in order to remove impurities such as phosphorus and sulphur that would otherwise weaken the steel. The result is a sturdy, relatively lightweight material that can be melted down and reused again and again.
The creation of virgin steel, however, relies heavily on choking coal, as well as the world’s non renewable, rapidly diminishing supply of iron ore as a core feedstock. This is a footprint the industry has not yet managed to wipe out – and with global steel demand continuing to be strong, it is going to take the right market signals to get the sector to shift to a more planet-friendly process.
Timber is the most long standing construction material, favoured for millennia for its strength, aesthetic and renewability. It has the lowest footprint of the trio, being a natural resource capable of storing the carbon absorbed over its lifetime even after it is felled.
According to the ABC, as much as 50 per cent of dried timber’s weight is the result of sequestered carbon that has been absorbed from the atmosphere and solidified. New South Wales Timber estimate the average timber home contains around seven tonnes of sequestered carbon in its frame alone.
The downside of timber is when its production is poorly managed. The hard fact is that Australia has not been taking steps to ensure a long-term supply of construction-suitable hardwoods and softwoods. The management of state forests in both New South Wales and Victoria has been coming under heavy fire recently, due to the logging of habitat for endangered species including Victoria’s yellow-bellied glider and key koala habitat in New South Wales.
Importing timbers also has its negatives, including the carbon emissions created by its transportation, and potential clearing of habitat, soil erosion, illegal logging, forced labour or animal cruelty where timber is not third-party certified.
Tim Grant of Lifecycle Strategies says “there is no such thing as a sustainable material”. Rather there are good uses of materials and not so good uses.
Ask what you want the material to do, where you might source it from, and how long it could achieve this goal.
The solution is then to take advantage of the material’s best properties in the given situation, reusing if and where possible.