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Title: Use of Mid- and Near-Infrared Spectroscopy to Track Degradation of Polyactide Eating Utensils and Containers During Composting

Author
item Mulbry, Walter
item Reeves Iii, James
item Millner, Patricia

Submitted to: Internet Journal of Vibrational Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2012
Publication Date: 1/16/2012
Citation: Mulbry III, W.W., Reeves III, J.B., Millner, P.D. 2012. Use of Mid- and Near-Infrared Spectroscopy to Track Degradation of Polyactide Eating Utensils and Containers During Composting. Internet Journal of Vibrational Spectroscopy. 109:93-97.

Interpretive Summary: Concern over landfill-generated methane has led to increasing efforts to divert organic materials in municipal waste from landfills to treatment facilities such as compost sites. Development and use of consumer products composed of biodegradable polymers such as polylactide (PLA) is part of the same trend. However, there is a wide range of composting practices within the industry and it is important to establish the fate of these polymers within different products and formulations. However, it can be difficult to track these polymer-based products within compost piles because of the abundance of dark organic material in compost. Near-infrared spectroscopy (NIRS) has been used for decades for quantitative analysis of many agricultural products including forages, grains and foods, and more recently has become a powerful tool in the analysis of pharmaceutical ingredients and products. Mid-infrared spectroscopy (MIRS) has been used for more qualitative investigations of a wide range of materials. The objective of this study was to investigate the potential of MIRS and NIRS for both, understanding the degradation of polylactide based food containers and utensils in compost piles. PLA-based forks incubated within static food waste compost piles lost 30 to 40% of their initial mass within 6 weeks. PLA forks unearthed from a comparable year-old food compost pile lost 65% of their initial mass. NIRS and MIRS performed on dried ground fork material suggests that the forks are composed of PLA resin and either starch or cellulose. Results demonstrate that the starch/cellulose component is preferentially degraded and that the PLA appears to accumulate and may not degrade at all under these conditions. Results suggest that it should be relatively easy to determine both, the state of degradation and the amount of PLA derived residue remaining in composted materials using either spectral range.

Technical Abstract: Near-infrared spectroscopy (NIRS) has been used for decades for quantitative analysis of many agricultural products including forages, grains and foods, and more recently has become a powerful tool in the analysis of pharmaceutical ingredients and products. Mid-infrared spectroscopy (MIRS) has been used for more qualitative investigations of a wide range of materials. The objective of this study was to investigate the potential of MIRS and NIRS for both, understanding the degradation of polylactide (PLA) based food containers and utensils in compost piles. PLA-based forks incubated within static food waste compost piles lost 30 to 40% of their initial mass within 6 weeks. PLA forks unearthed from a year-old food compost pile lost 65% of their initial mass. Results from NIRS and MIRS performed on dried, ground fork material suggests that the forks are composed of PLA resin and either starch or cellulose. Results demonstrate that the starch/cellulose component is preferentially degraded and that the PLA appears to accumulate and may not degrade at all. Results indicate that it should be relatively easy to determine both the state of degradation and the amount of PLA derived residue remaining in composted materials using either spectral range.