Humanity consumes around 100 Gt of materials annually and, despite a plethora of directives and strategies designed to support the development of a circular economy, the rate of recycling, which currently stands at 8.6 %, has declined from earlier years. Globally, the building sector is responsible for about 36% of energy use, 39% of CO2 emissions, and half of all materials consumed. To highlight the magnitude of the problem, it has been estimated that new infrastructure could consume 35-60% of the remaining carbon budget by 2050 even if global warming is limited to 2°C. The built environment clearly has a massive environmental impact, yet at the same time there is an enormous opportunity to make an impact, by altering how buildings are constructed. Recent years have seen a renaissance in wood construction, largely driven by its potential to reduce the environmental impact of construction; it has even been postulated that increasing the use of engineered timber in midrise building could help turn building into a global carbon sink.
To maximize climate change mitigation potential, it is desirable to promote the adoption of wood construction as much as possible. According to UNFAO forest products statistics, global production of sawn wood and wood-based panels in 2018 amounted to 900 Mm3, much of which will be destined for long-lived applications in building construction. How much scope there is to increase the sustainable harvesting of timber for bioeconomy purposes (including wood construction) is open to debate, however, there emerging evidence to suggest that recirculating wood, will not only improve resource efficiency, but will also help reduce the environmental impact of wood construction. For this reason, there are an increasing number of published studies, as well as ongoing research, into wood cascading. Simply put, cascading aims to “do more with less” – to make use of the material (wood) more efficiently by using it again (and, perhaps, again) after its first use, in second life products, before eventually recovering the energy content.
Keywords: circular economy, recycling, built environment, wood construction, cascading.
Authors
Mark Hughes, Professor, Aalto University
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