Peer Review Report For: Deep geological disposal of plastic waste: Pros and cons [version 3; peer review: 2 approved, 2 not approved]

Plastic waste accumulation is a global environmental issue. Current methods (recycling, incineration, landfilling, etc.) are not a sustainable long-term solution and so far they cannot prevent continuous accumulation of plastic waste worldwide. This article introduces the concept of deep geological disposal (DGD) of plastic waste as an alternative strategy. The concept principally differs from the traditional landfilling. In the latter, plastic waste is affected by chemical, physical, and microbial factors that cause plastic fragmentation and environmental leakage. On the contrary, DGD isolates plastic waste in abandoned mines, quarries and caves, ensuring safe long-term containment of the waste and the possibility of its reuse as a raw material in the future. Another advantage of DGD is that these geological structures usually have transport infrastructure and storage facilities, and, as a result, they offer a more controlled environment with reduced risk of leachate, microplastic dispersion, and surface pollution. The paper discusses the practical, economic, and environmental aspects of the concept of DGD of plastic waste. The proposal does not offer to replace other available mechanisms of plastic waste management, it presents DGD as a complementary and potentially effective method for addressing non-recyclable and mismanaged plastic waste worldwide.