IADR Abstract Archives
Optimal Management of Resin-Based Composite Waste: Landfill vs. Incineration
Objectives: Waste resin-based composite (RBC) is predominately disposed of via landfill. This study aimed to determine whether incineration was a suitable alternative disposal route.
Methods: Duplicate samples of two RBCs were prepared; a commercially available RBC (CompA) and an in-house standard RBC containing the required range of monomers (CompB), in polymerised and unpolymerised states. These were placed in microcosms of either sterilised (121°C/15min) or non-sterilised landfill leachate for 28 days at 35°C and sampled regularly. Incineration (≈850°C for 2 hours) of polymerised and unpolymerised CompA and CompB utilising a controlled direct flame/kiln custom rig was performed and released gases collected. Incinerated RBC and unburnt controls were washed in both H2O and acetonitrile ultrasonic baths for 1 hour post-incineration and sampled.
Eluted monomers (triethylene glycol dimethylacrylate (TEGDMA), urethane dimethacrylate (UDMA), bisphenol-A glycidyl methacrylate (Bis-GMA), hydroxyethyl methacrylate (HEMA), and bisphenol-A (BPA)), gases, ions and compounds were quantified via solid phase micro-extraction, high-performance liquid chromatography, gas chromatography, ion chromatography and inductively coupled plasma mass spectrometry.
Results: Concentrations of BPA were higher in non-sterilised landfill leachate samples for CompA (2.9x) and CompB (4.6x) compared with sterilised leachate samples. Conversely, concentrations of TEGDMA and UDMA were generally higher in sterilised samples. There was no significant difference for concentrations of Bis-GMA between leachate samples. Incineration resulted in significantly less overall elution of BPA, TEGDMA and UDMA compared to landfill disposal concentrations.
Conclusions: Bacteria-mediated degradation of RBC occurs in landfill leachate with a resultant increased release of BPA, a recognised xenoestrogen. This could increase the potential environmental impact of RBC when disposed of in landfill. Monomers are released from polymerised and unpolymerised RBC into landfill leachate over a prolonged period of time. Incineration of RBC results in significantly lower concentrations of monomers, elements and ions released into the environment. Incineration is a viable alternative waste disposal route for RBC, with a potentially lower environmental impact.
Methods: Duplicate samples of two RBCs were prepared; a commercially available RBC (CompA) and an in-house standard RBC containing the required range of monomers (CompB), in polymerised and unpolymerised states. These were placed in microcosms of either sterilised (121°C/15min) or non-sterilised landfill leachate for 28 days at 35°C and sampled regularly. Incineration (≈850°C for 2 hours) of polymerised and unpolymerised CompA and CompB utilising a controlled direct flame/kiln custom rig was performed and released gases collected. Incinerated RBC and unburnt controls were washed in both H2O and acetonitrile ultrasonic baths for 1 hour post-incineration and sampled.
Eluted monomers (triethylene glycol dimethylacrylate (TEGDMA), urethane dimethacrylate (UDMA), bisphenol-A glycidyl methacrylate (Bis-GMA), hydroxyethyl methacrylate (HEMA), and bisphenol-A (BPA)), gases, ions and compounds were quantified via solid phase micro-extraction, high-performance liquid chromatography, gas chromatography, ion chromatography and inductively coupled plasma mass spectrometry.
Results: Concentrations of BPA were higher in non-sterilised landfill leachate samples for CompA (2.9x) and CompB (4.6x) compared with sterilised leachate samples. Conversely, concentrations of TEGDMA and UDMA were generally higher in sterilised samples. There was no significant difference for concentrations of Bis-GMA between leachate samples. Incineration resulted in significantly less overall elution of BPA, TEGDMA and UDMA compared to landfill disposal concentrations.
Conclusions: Bacteria-mediated degradation of RBC occurs in landfill leachate with a resultant increased release of BPA, a recognised xenoestrogen. This could increase the potential environmental impact of RBC when disposed of in landfill. Monomers are released from polymerised and unpolymerised RBC into landfill leachate over a prolonged period of time. Incineration of RBC results in significantly lower concentrations of monomers, elements and ions released into the environment. Incineration is a viable alternative waste disposal route for RBC, with a potentially lower environmental impact.