LCA Practices of Plastics and Their Recycling: A Critical Review

Recommendations for life-cycle assessment of recyclable plastics in a circular economy

Technologies that enable plastic circularity offer a path to reducing waste generation, improving environmental quality, and reducing reliance on fossil feedstocks. However, life-cycle assessment (LCA) methods commonly applied to these systems fall far short of capturing the full suite of advantages and tradeoffs. This perspective highlights inconsistencies in both the research questions and methodological choices across the growing body of LCA literature for plastics recycling. We assert that conducting LCAs on the basis of tonnes of waste managed vs. tonnes of recycled plastics yields results with fundamentally different conclusions; in most cases, analyses of recyclable plastics should focus on the unit of recycled product yielded. We also offer straightforward paths to better approach LCAs for recycling processes and plastics in a circular economy by rethinking study design (metrics, functional unit, system boundaries, counterfactual scenarios), upstream assumptions (waste feedstock variability, pre-processing requirements), and downstream assumptions (closed-loop vs. open-loop systems, material substitution). Specifically, we recommend expanding to metrics beyond greenhouse gases by including fossil carbon balances, net diversion of waste from landfill, and quantity of avoided plastic waste leakage to the environment. Furthermore, we highlight the role that plastic waste plays as a problematic contaminant in preventing greater diversion of all wastes to recycling, energy recovery, and composting, suggesting that plastics may hold a shared responsibility for the system-wide greenhouse gas emissions that occur when mixed wastes are landfilled.

Dynamic life cycle assessment of commercial and household food waste: A critical global review of emerging techniques

DLCA has been applied to several food waste streams, however, to date no critical assessment of its strengths, weaknesses, opportunities, and threats (SWOT) is available in the scientific literature. Accordingly, the present review aims to provide a comprehensive overview of the available literature on DLCA and its application to Household and Commercial Food Waste (HCFW) by providing critical assessment and perspectives for future research. The Population, Intervention, Comparison, and Outcome (PICO) framework for literature review was employed, with just 12 relevant studies identified between 1999 and 2022, highlighting a dearth of research on DLCA of food waste and the need for further research. Identified studies exhibit significant variations with respect to DLCA methodology, boundary settings, and data quality and reporting, with more attention typically given to combining conventional LCA with dynamic characterization models, thus making it difficult to draw conclusive findings or identify consistent trends. Additionally, most identified studies employed DLCA for a specific case study and comparison with traditional LCA outcomes was typically ignored; just one study presented the projected impact from both LCA and DLCA for the entire life cycle of a product. Employed functional/reference units ranged from specific quantities such as 1 kg of refined crystals or syrup, 1 g L-1 Sophorolipid solution, and 1 kg of dry food with packaging material, to broader indicators like 1 kg of biofuel or 1 MJ of primary energy. Monte Carlo simulation was the most frequently employed method for uncertainty analyses within identified studies. Sensitivity analyses were conducted in just 4 studies, but it was not always clearly reported. While DLCA is undoubtedly a more realistic approach to impact assessment, and thus likely more accurate, a need exists for increasingly standardized and regulated versions of DLCA for global and multi-criteria practices.

The Critical Role of Process Analysis in Chemical Recycling and Upcycling of Waste Plastics

There is an urgent need for new technologies to enable circularity for synthetic polymers, spurred by the accumulation of waste plastics in landfills and the environment and the contributions of plastics manufacturing to climate change. Chemical recycling is a promising means to convert waste plastics into molecular intermediates that can be remanufactured into new products. Given the growing interest in the development of new chemical recycling approaches, it is critical to evaluate the economics, energy use, greenhouse gas emissions, and other life cycle inventory metrics for emerging processes, relative to the incumbent, linear manufacturing practices employed today. Here we offer specific definitions for classes of chemical recycling and upcycling and describe general process concepts for the chemical recycling of mixed plastics waste. We present a framework for techno-economic analysis and life cycle assessment for both closed- and open-loop chemical recycling. Rigorous application of these process analysis tools will be required to enable impactful solutions for the plastics waste problem. Expected final online publication date for the Annual Review of Chemical and Biomolecular Engineering, Volume 13 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.