in partnership with
The ‘circular economy’ is a term that is widely used, but not always considered accurately. In terms of the building and construction sector, here are a few thoughts for consideration.
A recent report from Circular Economy (16th January 2023) reinforced that the built environment is responsible for 40% of global GHG emissions, and that the production and use of cement accounts for 7% of the total carbon dioxidereleased into the atmosphere. This places a big onus on the sector to reduce emissions in any global move to carbon reduction and net zero. Additionally, operation of buildings uses over half of the planet’s electricity consumption.
A circular economy, by definition, implies that materials extracted from the planet’s resources are used and then recycled for 100% reuse. The Global Circularity Gap report 2023 reports, however, that the global economy is only 7.2% circular across all materials and falling year on year – from 9.1% in 2018 and then 8.6% in 2020. This continuing trend is partly accounted for by the continuing increase in the rate of material extraction.
This report states that it would be possible to fulfil the needs of the planet’s population with just 70% of the materials currently used, if a circular economy model is adopted. Another way of putting this is that the global need for material extraction could be reduced by about 1/3.
The built environment is one of the four key systems where making transformational circular changes can make it possible to reverse the current overshoot on planetary sufficiency.
In terms of circularity it is worth noting that it will never be possible to achieve 100% circularity, there will always be some materials that cannot be recirculated due to chemical changes, or may be degraded after each re-use cycle. The big challenge at the moment is that the capacity for recycling is nowhere near the potential demand for materials.
Crucial construction materials, for example, are already becoming scarce due to overuse, exacerbated by a lack of urban planning contributing to urban sprawl, high car dependency, air and noise pollution and excessive material use. Lack of circular design and integrated planning in the past means that buildings already in use are major carbon emitters; construction and demolition of buildings accounts for nearly 1/3 of global energy consumption as well as a similar percentage of waste generated (ref 86 from Global Circularity Gap report 2023).
The potential to improve the efficiency of resources (whether traditional building materials or synthetic materials such as plastics and textiles, varies between developed countries and those whose economies are still developing. Provision of housing and services for the world’s rapidly urbanising population sector will inevitably require additional material use, but in already urbanised countries there is considerable scope for reducing demolition and re-use of materials to avoid and reduce unnecessary extraction. This can apply to non-metallic minerals such as
Although the built environment occupies only around 1% of global land surface, the effects of mineral extraction, building, waste deposits etc are responsible for about 25% of all land system change including habitat destruction and biodiversity loss. A transition from a linear to one using circular economy design principles could allow a significant reduction in impacts on the planet.
From the UNEP report 27th January 2023 (https://www.unep.org/news-and-stories/story/plastic-treaty-progress-puts-spotlight-circular-economy)
This report provides estimates for plastic production of 460 million tonnes of plastic a year with the expectation that this will triple by 2060, in line with other recent estimates. A report for UNEP from September 2022 indicated that less than 9% of plastic waste is effectively recycled, only about 60% of that actually collected for recycling. Approximately 46% still goes to landfill, 22 per cent becomes litter and 17 per cent is incinerated.(https://wedocs.unep.org/bitstream/handle/20.500.11822/41263/Plastic_Science_E.pdf).
This report also states that: “There is increasing clarity regarding the links between plastic and human and environmental health. The links between plastic with its associated chemicals and plastic pollution with its detrimental effects on human health and the environment are increasingly clear, although plastic’s contribution to the global burden of disease across its life cycle has not been yet well quantified”. This counters claims from the plastics and petrochemicals industry that there is no evidence for adverse effects of plastic on human health.
Based on current estimates of lifespan of different plastics, plastics from construction currently entering waste streams have on average been in use since around 1970. Those being used now in the building and construction sector will largely be entering the waste stream in around 2070. So what the industry does now in terms of using plastic products will have long-term implications for environmental health or pollution. https://plasticseurope.org/wp-content/uploads/2022/06/PlasticsEurope-CircularityReport-2022_2804-Light.pdf)
45% of post-consumer recycled plastic is currently used in the building and construction industry. So it is reasonable to assume that much of this recycled plastic will re-enter the waste stream on average around 2070 (on the optimistic lifecycle assumption that these products are of comparable durability with those entering the waste stream from virgin plastics).
Uekert et al (ACS Sustainable Chem. Eng. 2023, 11, 965−978) have reviewed material flows and different methods of recycling looking at efficiency, economics, quality of recyclate inter alia. They have shown that mechanical recycling are significantly more cost effective than competing technology, whereas chemical recycling methods provide higher quality material.
The establishment in 2022 of negotiations for a Global Plastic Treaty have also been the subject of widespread comment. It has been pointed out (Wang and Praetorius , DOI: 10.1021/acs.estlett.2c00763 Environ. Sci. Technol. Lett. 2022, 9, 1000−1006) that plastics are indeed complex materials including not only carbon/hydrogen polymers but also additives and processing aids to improve functionality in end use. Over 10,000 different chemical substances have been used or introduced during the reactions involved in plastic production, many of which are known to be hazardous to human, plant and animal health, and persist for many years in the environment. Many of the chemicals used hamper the efficiency and safety of recycling processes. Wang and Praetorius propose three key considerations which need to be incorporated in the Global Plastic treaty to ensure its effectiveness:
In this context it is worth noting a report from The Guardian in 2021 that US PFAS manufacturers had spent over $61m in the previous two years lobbying government to prevent restrictions on PFAs: https://www.theguardian.com/environment/2021/apr/26/us-chemical-companies-lobbying-donation-defeated-regulation
There are very specific issues associated with the development of a circular economy in plastics, and it is questionable whether we have time to wait for the negotiation and changes in practices needed to design sustainable recyclable materials with minimal use and emission of hazardous chemicals. Use of sustainable alternatives must become a priority wherever possible.
