Environmental Life Cycle Assessment of Nanosilver Enabled Bandages

Transcription

1 Environmental Life Cycle Assessment of Nanosilver Enabled Bandages Leila Pourzahedi Matthew J Eckelman Nov 4, 2013

2 Outline Introduction and Motivation Research Questions Methods Results Conclusion Sigma-Aldrich, TEM images of 20, 60 and 100 nm silver nanoparticles 2

3 Introduction and Background Used AgNPs as colloidal silver 1 from over 100 years ago Today, engineered AgNPs are being used in a wide range of products with direct human and environmental exposure 1 Nowack et al.,

4 AgNP Production and Consumption Medical ~400 metric tons produced in 2010 WIP 1% emissions to air Keller et al., Global life cycle releases of engineered nanomaterials, J Nanopart Res,

5 Overarching Research Questions Which life cycle stages dominate for different nanomaterials and impact categories? (production vs. releases) How does the introduction of nanomaterials affect the life cycle impacts of a product? (does being nano-enabled matter?) 5

6 Production Impact Domination or Release? Ecotoxicity (CTUe) Eckelman et al., New perspectives on nanomaterial aquatic ecotoxicity, Environ. Sci. Technol., 2012 (Non-CNT) production emissions dominate (CNT) releases for ecotoxicity What about for a different nanomaterial? 6

7 Nanomaterials vs. Nano-Enabled Products Most studies look at pure nanomaterials - what is the contribution of nano to LC impacts of nano-enabled products? Fabrication steps Material and energy inputs Dahlben et al., Environmental LCA of a CNT-Enabled Semiconductor Device, Environ. Sci. Technol CNT synthesis has insignificant impacts, < % What about for other nano-enabled products? 7

8 LCA of Ag-NP Impregnated Bandages Ag-NP has higher indicated bioactivity Bandages have higher NM concentrations than electronics Past work on textiles Nano silver T-shirt LCA (Walser et al.) Nano silver sock LCA (Meyer et al.) Marambio-Jones et al., A review of the antibacterial effects of silver nanomaterials, J Nanopart Res,

9 Study Methods 7 production routes were modeled Chemical reduction, Green synthesis, Physical synthesis 3 Different bandage types were considered One predetermined end of life scenario No use phase Contribution of AgNP to bandage Contribution of AgNP to EoL Input material AgNP synthesis Bandage manufacture Application End of life incineration Emissions Tailings Emissions Emissions Emissions Release Emissions Landfill 9

10 Data collection: AgNP Synthesis Chemical reduction Green synthesis Physical synthesis 10

11 Data collection: Bandages Composition data obtained from Wounds International and a study by Parsons et al., (2005) For a 10 cm x 10 cm bandage 104 mg AgNPs 12.6 mg AgNPs 111 mg AgNPs 11

12 LCA Modeling Methods SimaPro was used as the modeling tool ecoinvent adjusted for U.S. energy system (US-EI) database TRACI 2.1 used as the impact assessment method Wet Chemistry Method Source Section Material Amount Unit Corresponding LCI unit process CR with Sileikaite Input Silver 1.58 kg Created trisodium et al., 2006 nitrate citrate Trisodium 0.80 kg Created Citrate Water 0.14 kg Tap water, at user/rer with US electricity U Output Citric acid 0.59 kg Emissions to water> Citric acid Sodium 0.79 kg Emissions to water> Nitrate Sodium nitrite Hydrogen 0.01 kg Emissions to air> Hydrogen Oxygen 0.12 kg Emissions to air> Oxygen 12

13 % Results: AgNP synthesis CR-EG: significant use of EG FSP: high silver input and electricity Green: pesticide, fertilizer & transport in potato harvesting CR-TSC CR-SB CR-EG Green FSP LFS PA To reduce impacts from production, assessments of all options are suggested 13

14 Global Warming Ecotoxicity Results: Contribution of AgNP to Acticoat 7 Impacts from sulfidic mining tailings Impacts from silver mining (machinery and electricity) and air freight CR-TSC AgNPs FSP AgNPs CR-TSC AgNPs FSP AgNPs 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Nano silver HDPE Polyester Paper, supercalendred Electricity mix AgNPs dominating bandage production impacts 14

15 Results: Comparison Across Bandages 111 mg 12.6 AgNPmg AgNP 104 mg AgNP 100% Silvercel Aquacel Acticoat 7 80% 60% 40% 20% 0% Silver concentration on bandage impacts the ultimate outcome (Lower silver concentrations, lower environmental impacts) 15

16 Results: Contribution of AgNP to EoL Plastics incineration 10% Packaging incineration 2% Packaging incineration 3% Ecotoxicity Global Warming Silver incineration 88% Plastics incineration 97% From 1% silver release Release of silver from WIP greatly affects the ecotixicity impacts 16

17 Results: Production vs Disposal? Our first question finally answered 100% Bandage manufacturing Bandage disposal 80% 60% 40% 20% 0% Global warming Ecotoxicity Non-nano emissions from production results in higher impact levels 17

18 Concluding Remarks Environmental impacts of the production phase dominates over all other stages Silver is the main contributor to the impacts of production phase Benign reagents are not necessarily preferable on a life cycle basis Parallel / Future Work Study of all AgNP-enabled product categories SNM: [NSF Award # SNM ] EMI shielding; chemical sensors; lithium-ion batteries 18

19 Thank you! Leila Pourzahedi 19