Differentiating low-carbon waste management strategies for bio-based and biodegradable plastics under various energy decarbonization scenarios.

Abstract

Bio-based and biodegradable (bio-)plastics are heralded as a key solution to mitigate plastic pollution and reduce CO₂ emissions. Yet, their end-of-life treatments embodies complex energy and material interactions, potentially leading to emissions through incineration or recycling. This study investigates the cradle-to-grave, emphasizing the waste management stage, carbon footprint for several types of bio-plastics, leveraging both GWP100a and CO₂ uptake methods to explore the carbon reduction benefits of recycling over disposal. Our findings indicate that in scenarios characterized by carbon-intensive electricity, using polylactic acid (PLA) as an example, incineration with energy recovery (-1.6316 kg CO₂-eq/kg, PLA) yields a more favorable carbon footprint compared to chemical recycling (-1.5317 kg CO₂-eq/kg, PLA). In contrast, in environments with a high proportion of renewable energy, chemical recycling is a superior method, and compared to incineration (-1.4087 kg CO₂-eq/kg, PLA), the carbon footprint of chemical recycling (-2.0406 kg CO₂-eq/kg, PLA) are significantly reduced. While mechanical recycling presents considerable environmental benefits, its applicability is constrained by the waste quality, especially in the case of biodegradable plastics like PLA. In addition, the degradation of biodegradable plastics such as PLA was modeled during compost and anaerobic digestion processes. This enables us to quantify the specific biogenic carbon emissions released during these processing steps, revealing the direct emissions with dynamic degradation. This study highlights the importance of tailoring bio-plastic waste management strategies to support global energy decarbonization while understanding their life-cycle carbon metabolism to effectively tackle plastic pollution and climate change.