In a publication on May 10, 2021 in the peer-reviewed journal Sustainable Chemistry and Engineering, researchers Zhanyun Wang and Stefanie Hellweg from ETH Zurich analyzed the major causes of chemical losses throughout a chemical’s life cycle and developed suggestions to stem those losses in order to improve chemical circularity. The authors found ten causes of chemical loss from manufacturing through to product end-of-life with the majority of losses at end-of-life. The end-of life losses are split into those “related to product design,” like impurities in the mix or difficulties separating components, and losses “related to the overall system” such as a lack of recycling incentives or regulatory incompatibility. The authors suggest two changes to the current chemical assessment procedure early in production to create fewer losses and along the rest of the supply chain.
The first change is to adapt current hazard and risk assessment procedures to account for multiple use cycles. In plastics, for example, most focus is on reusing the polymer with less effort placed on considering the chemical additives within the plastic. When additives aren’t accounted for, hazardous chemicals may inadvertently end up in products that increase human exposure, including food packaging (FPF reported here and here). Recent work in Current Opinion in Green and Sustainable Chemistry by Nicolò Aurisano et al. reviewed the more than 6’000 chemicals found in plastic products and the current assessments used to measure human and environmental impacts. The authors suggest over 1’500 chemicals be immediately replaced in plastic products and propose policy changes that support a circular economy for plastics. Wang and Hellweg provide lead-acid batteries as an example of a system where, when done responsibly, it is possible to separate, clean, and reuse battery components in a circular manner.
After assessing any health hazards around multiple use, the second change Wang and Hellweg suggest to improve chemical circularity is to directly assess how the chemical affects circularity of whatever product it is used in. The “circularity assessment” first looks at whether the chemical itself is circular, (yes or no), and then whether it impacts the circularity of whatever it is used with (inhibit, enable, or no impact). “A chemical [that] is circular itself and may enable, or has no impacts on, the circularity of others are most desirable and can be directly approved for use or promoted. When a chemical is noncircular itself and may inhibit the circularity of others [it] would need to be subject to further essential-use assessments.” Hydrochloric acid (HCl, CAS 7647-01-0) in the steel industry is an example of a recyclable chemical that enables circularity. After steel plates are rolled, HCl poured over the plates removes rust, and the leftover liquid can be collected and recycled, regenerating the acids and recovering metals. Meanwhile, carbon black in plastics makes the recycling and reuse of the polymer difficult. Carbon black is often used in non-essential roles such as to darken fast food containers, and so in many use cases alternatives may be better.
Creating a circular chemical economy will require collective work by the chemical and policy community (FPF reported). For a circular system to work, the authors state that there needs to be more transparency in product manufacturing, universally accepted standards, and policies that coherently support and encourage good practices.
References
Wang, Z. and Hellweg, S. (2021). “First Steps Toward Sustainable Circular Uses of Chemicals: Advancing the Assessment and Management Paradigm.” ACS Sustainable Chemistry and Engineering, (available online May 10, 2021).
Aurisano, N. et al. (2021). “Enabling a circular economy for chemicals in plastics.” Current Opinion in Green and Sustainable Chemistry, Pre-proof: (available online May 7, 2021).
