Case studies on MWCNT nanosilver and nanotitanium dioxide

Case study 1: MWCNTs in a PEM Fuel Cell

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Introduction

Using the nanoSCAN tool: Risk-Benefit analysis

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1. Environmental benefitsProduction

UseEnd of Life

2. Economic benefitsMarket potential

ProfitabilityDevelopment stage

3. Societal benefitsTechnological breakthrough

High quality labour developmentImproving global health or food

Negative Neutral Positive

Benefits

• Low to moderate environmental benefits are expected at all stages of the life cycle.

• Moderate economic benefits are expected from the forecast market potential and profitability.

• High societal benefits are expected due to the innovative technology and the development of a skilled labour force.

Situation: Producing energy so clean that water is the only direct emission from the exhaust pipe is just a part of the attractive concept behind the fuel cell (FC). However, the design and development of FCs has long been hindered by the very expensive platinum catalyst required: high demand for mining platinum resources diminishes both the environmental and economic advantages of FCs. Nanoparticle: Multi-walled carbon nanotubes (MWCNTs) are used, instead of carbon black (CB), as they provide a much greater surface area of supporting structure for the platinum electrocatalyst. Aim: First, apply the nanoSCAN tool, and then use Life Cycle Assessment (LCA) and Risk Assessment (RA) in order to compare the risks and benefits of the two FC systems:

a) a conventional FC using CB to support the platinum electrocatalyst; b) a FC using MWCNTs to support the platinum electrocatalyst.

Expected Benefits: Replacing CB with MWCNTs is expected to lead to an increased surface area and a much better distribution of the platinum particles. These two improvements should allow a substantial reduction in the amount of platinum necessary to maintain FC efficiency. Both FC systems should have the same useful life and energy efficiency (fuel to electricity). The benefits are thus expected to occur in the production phase.


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0.00 0.33 0.67 1.00

4. Public health & environmental risks

System knowledge

Potential effect

Potential input into the environment

5. Occupational health risks

Production of nanomaterial

Processing of nanomaterial

Application of nanoproduct

6. Consumer health risks

Low Medium High

Risks

Using the nanoSCAN tool: Decision-making

Interpretation of results Benefits: The nanoSCAN results suggest that, this application promises to be a successful example of MWCNTs use. Considerable benefits are expected from different stages in the life cycle. Risks: Occupational health risks are high, stemming mainly from the high potential for MWCNT toxicity. Exposure, however, seems to be rather low. Decision: The results of this case study suggest going ahead with development as long as exposure risks can be reduced to an absolute minimum.

• There are high risks for workers in the production stage. Moderate risks exist for public health and the environment. These risks come from the high potential for toxic effects exhibited by MWCNTs.

• Occupational health risks are high and arise from nanomaterial production.

• There are no risks for the consumer.


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Applying Life Cycle Assessment (LCA) and Risk Assessment (RA): Risk-Benefit Analysis

Results of Life Cycle Assessment Calculations [Environmental impact split in most relevant impacts]

Results of Risk Assessment Calculations

• The benefits are explained by the substantial reduction in the demand for platinum in the production of a PEM FC using MWCNTs.

• The use phase is the dominant life cycle stage for a PEM fuel cell. There is no difference between the two types of FC when this phase is considered alone.

Basic assumptions: Fuel conversion efficiency, life expectancy, power output and specific power density are equal for both systems. Socio-economic and environmental risk assessments are not included in the in-depth analysis, therefore the risk assessment is limited to occupational risks.

• Occupational health exposure scenarios show the production and processing of MWCNTs to be the main occupational risk.

• A moderate health effect was obtained for MWCNTs based on relatively low exposure per functional unit, but a relatively high hazard. A relatively low health risk was obtained for CB.

• The potential variation in occupational health risk is largely due to the uncertainty of actual exposure levels.

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MWCNT CB MWCNT CB MWCNT CB MWCNT CB

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Climate change Human Health Human toxicityParticulate matter formation Climate change EcosystemsMetal depletion Fossil depletionRest

Production Use phase End of Life Total


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Combining LCA and RA results for decision making

Conclusions from the combined analyses

Disclaimer: This case study is designed on the basis of current knowledge on nanomaterials. The development of knowledge in the field of nanomaterials is progressing fast, therefore the partners of the LICARA project cannot give guarantees as to the correctness of the information herein. New knowledge can influence the conclusions of this case study (July 2014).

Interpretation of results Benefits: The PEM FC using MWCNTs provides 21% greater environmental benefits than the FC using conventional CB during the production and end-of-life phases, even if rigorous recycling is assumed (95% recycling rate for platinum). The use phase gives similar results for both products. Risks: The shadow costs of consumer and occupational health effects are much smaller than the costs in LCA results. Next steps: Based on the precautionary principle, ensure that exposure to MWCNTs is kept to an absolute minimum.

From nanoSCAN: The use of MWCNTs in PEM fuel cells is a promising example of a nanomaterial application. The nanoSCAN shows considerable benefits across different stages of the life cycle. The risks are moderate and stem mainly from the high potential for MWCNT toxicity. Exposure, however, seems to be rather low. From the in-depth LCA and RA: The LCA results reveal that the benefits of using MWCNTs are about 20% over the product’s life cycle (if the use phase is not taken into account). The results from RA show a moderate MWCNT health effect based on relatively low exposure, but a relatively high hazard. What next? The nanoSCAN and the in-depth LCA and RA assessments confirm the benefits of the PEM fuel cell using MWCNTs. Exposure to MWCNTs during production should be reduced to an absolute minimum. If this can be ensured, the recommendation would be for product development to be given the go-ahead.

Case study 2: nanosilver in a microfibre cloth

1

Introduction

Using the nanoSCAN tool: Risk-Benefit Analysis

• Medium to high environmental benefits are expected during all stages of the product’s life cycle.

• Medium benefits are expected for market potential and profitability. The high benefits come from the development stage.

• High benefits are expected across all societal aspects.

Situation: A microfibre cloth is used to clean household (such as in kitchens or bathrooms.) or industrial surfaces. The biocides (nanosilver or triclosan) in the microfibre cloth inhibit the growth of micro-organisms (mould or bacteria) in a wet storage and use conditions. The microfibre cloth consists mainly of PET fibres and the biocide. Nanoparticle: Silver ions have antimicrobial properties. Nanosilver incorporated into the textile fibres release ions which protect the fibres from microbial infection. Aim: First, apply the nanoSCAN tool, and then use Life Cycle Assessment (LCA) and Risk Assessment (RA) in order to compare risks and benefits of two products:

a) a microfibre cloth containing silver nanoparticles; b) a microfibre cloth containing triclosan (organic biocide).

Expected Benefits: Applying nanosilver to the microfibres is expected to protect the cloth better and longer. Clear advantages are expected in the use phase since the cloth treated with nanosilver can be stored wet due to its resistance against microbes. The energy used for drying is thus saved.


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• There are low risks expected to consumer health.

• Medium occupational health risks are expected.

• Public health and environmental risks are expected to be low. Low risks are driven by the moderate potential toxicity of silver ions, and the very low expected exposure of environmental compartments.

Interpretation of results Benefits: The nanoSCAN results suggest that this application promises to be a successful example of nanosilver use. Considerable benefits are expected from different stages in the life cycle. Risks: The risks are low to medium. Medium risks are expected for occupational health, while low risks are expected for the environment, public health and consumers. Decision: The results of this case study suggest going ahead with development as long as exposure risks can be minimized.


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Results of Life Cycle Assessment Calculations

[Environmental impact split in most relevant impacts]

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nano

Ag

tricl

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nano

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sClimate change Human Health Climate change EcosystemsHuman toxicity Particulate matter formationNatural land transformation Metal depletion

Production Use phase End of life Total

Results of Risk Assessment Calculations

Basic assumptions: While elaborating the case study it was found that triclosan is incorporated into the microfibre in the same way as nanosilver (nanoAg). Thus, both products can be stored wet and the use phase for both products is the same (no energy savings in the use phase). Socio-economic and, environmental risk assessments are not included in the in-depth analysis, therefore the risk assessment is limited to occupational risks.

• There are no environmental benefits for any of the

new product’s life cycle stages. • Neither biocide has any impact on the overall

performance of the study.

• Occupational health exposure scenarios show the

production of nanosilver to be the main occupational health risk.

• No inhalable health risks were identified for the conventional triclosan product.

• The uncertainty within occupational health risk is large.


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Applying Life Cycle Assessment (LCA) and Risk Assessment (RA): Decision-making



Interpretation of results Benefits: Environmental impacts reveal no benefits for the nanosilver product. Risks: On the contrary, there are low risks to human health and the environment. Shadow costs of consumer and occupational health effects are 8 orders of magnitude smaller than those from LCA results. Next steps: Check whether other functional benefits for the product can be found. Ensure societal and economic benefits.

From the nanoSCAN: A microfibre cloth with nanosilver is a successful example of using nanomaterials. The benefits for the environment, the economy and society are high. The low risk comes from the potential effects on public health and the environment. From the in-depth Life Cycle Assessment and Risk Assessment: Analysis using the nanoSCAN leads to substantially higher environmental benefits, while the results from the full assessment show no benefits. The difference in the results between the two approaches to environmental benefits is explained by the greater systemic knowledge built up by the full assessment. The projected benefits for electricity savings during the use phase could not be confirmed since the triclosan provides a similar level of protection to the cloth as nanosilver. What next?: A potential next step would be to verify whether there are clear economic or societal benefits and whether the microfibre cloth treated with nano-Ag can provide better/additional functions in comparison to the microfibre cloth treated with triclosan.

Case study 3: nanosilver-coated door handle for infection prevention

1

Introduction

Using the nanoSCAN tool: Risk-Benefit Analysis of the nanosilver coating compared to a conventional (non-nano) coating

• The nanosilver coating is expected to provide economic and societal benefits.

• Environmental benefits are expected to be limited.

• Economic and societal benefits stem from the new functionality.

Situation: Hospital-acquired infections (HAIs) require patients to receive additional medical treatment, lengthen hospital stays and can even lead to deaths. Microbes living on surfaces in hospitals and transferred by hand contact are one of the causes of infection. Anti-microbial surface-coatings can reduce the number of HAIs. Nanomaterial: Silver ions have antimicrobial properties. Nanosilver can efficiently release silver ions when incorporated into a coating. In this case study, hospital door handles are coated with a water-based polysiloxane-nanosilver coating to reduce the number of hospital acquired infections. Aim: The main objective was to determine the environmental, human and social performance of nanosilver coated door handles. For this purpose life cycle assessment (LCA), risk assessment (RA) and socio-economic assessment were applied.


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Interpretation of results

Benefits: The nanoSCAN results suggest that clear economic and societal benefits are to be expected. The environmental benefits are limited.

Risks: The risks are low to medium. Risks arise from the potential effects on human health and the environment. Occupational health risks, assessed using Stoffenmanager Nano are medium. As the product is only intended for professional use, consumer risks are low.

Decision: The results of this case study suggest going ahead with development as long as exposure risks can be reduced to an absolute minimum.

• Low public health and environmental risks as the system is well defined and there is a low pollution to the environment.

• Medium occupational health risks exist because of the medium potential hazard and low-to-medium exposure of workers to nanosilver.

• As consumers are only incidentally dermal exposed to the nanocating consumer risks are low.


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Applying Life Cycle Assessment (LCA) and Risk Assessment (RA): Risk-Benefit Analysis of a nanosilver polysiloxane coating compared to doing nothing

• Environmental impacts and health risks and benefits are expressed in Euros.

• Even conservative assumptions about the nanosilver coating show a net socio-economic benefit.

• The benefits of a lower infection rate outweigh all direct and indirect costs.

• Occupational health exposure scenarios show the production of nanosilver to be the main occupational risk;

• The uncertainty in occupational risk is small as the difference between the minimum and maximum scenarios is within the same order of magnitude.

• Main environmental impacts are related to the production of polysiloxane, to silver emissions into the air during coating and to emissions to soil via waste water used to clean door handles.

• The impacts which exhibit the largest potential risks are human toxicity and eco-toxicity.

Basic assumptions: The water-based nanosilver polysiloxane coating is applied using a cloth and re-applied every two years. The socio-economic evaluation combines environmental impacts, occupational risk and application costs. Results shown are for 1 m2 of coated door handles per year.


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Applying Life Cycle Assessment, Risk Assessment and Socio-Economic Assessment: Decision-making



From the nanoSCAN: Coating door handles with nanosilver is, compared to a conventional coating, a more or less successful example of using nanomaterials. The benefits to the economy and society are good. There are low to medium human and environmental health risks. As long as the exposure risks can be reduced to an absolute minimum this nanomaterial application would get the go-ahead. From the in-depth Life Cycle Assessment and Risk Assessment: The polysiloxane and silver emissions that occur during coating are main environmental impacts. Emissions to waste water due to use and cleaning of door handles are also of importance. Occupational health exposure scenarios show the production of nanosilver to be the main occupational risk. From socio-economic analysis: The benefits of infection reduction always outweigh the societal costs. What next? The in-depth LCA and RA, but especially the socio-economic assessment, confirm the benefits of coating door handles to reduce hospital-acquired infections. Occupational exposure during nanosilver production should be reduced as much as possible. Reducing silver emissions to the sewer system has the potential to reduce environmental impacts. The final conclusion would be to go ahead with nanosilver coating.

Interpretation of results Benefits: The benefits of preventing hospital-acquired infections always outweigh the direct and indirect costs. Costs: The direct costs to the personnel have the largest contribution to both direct and indirect costs. The indirect environmental and occupational costs are almost negligible. Next steps: Coating more surfaces than just door handles will further reduce hospital-acquired infection rates.

Case study 4: Self-cleaning facade nanocoating

1

Introduction

Using the nanoSCAN tool: Risk-Benefit analysis

• Moderate environmental and economic benefits, as well as rather low societal benefits, are expected to be achieved when using an additional nanocoating on the facade.

• The use phase results are expected to result in high benefits because of reduced paint consumption. High benefits can also be expected due to the market potential.

Situation: Paint is applied to a facade to protect a building from environmental weathering by wind, rain, ice and solar radiation. The paint’s functions can be enhanced so that the facade is partly “self-maintaining” by the application of a top coating containing suitable nanoparticles. Nanoparticle: Nanotitanium dioxide (nano-TiO2) is used due to its ability to decompose organic materials, pollutants, solids or gases in the presence of water, oxygen and solar radiation. Aim: First, apply the nanoSCAN tool, and then use life cycle assessment (LCA) and risk assessment (RA) in order to compare the benefits and risks of the two different options for the outdoor facade coating:

(a) a conventional paint, containing no nanoparticles; (b) a combination of conventional paint with an additional coating layer containing nano-TiO2.

Expected Benefits: A facade coated with an additional coating layer containing nano-TiO2 is expected to require less maintenance (cleaning). The useful life of the paint layer should be substantially prolonged. Over the life-time of a building this leads to a considerable reduction in paint consumption.



• Medium risks are expected for the area of public health & environmental risks, that are mainly driven by those of potential inputs into the environment and to a lower extent by the toxicity of nano-TiO2.

• High occupational health risks are expected in the manufacturing and processing phases.

• Medium risks are expected for consumers.

Interpretation of results Benefits: The nanoSCAN results suggest that this application might prove to be a successful example of nanoparticle use. Considerable benefits are expected, especially in the use phase. Risks: The risks in the production phase are high, stemming mainly from the potentially high toxicity of nano-TiO2. The probability of being exposed, however, seems to be rather low. Decision: The results of this case study suggest going ahead with development as long as potential exposure risks can be reduced to an absolute minimum.


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Results of Life Cycle Assessment Calculations [Environmental impact split in most relevant impacts]

Results of Risk Assessment Calculations [Occupational Health risks of the nano-TiO2 case]

• The occupational health risks are examined for the nano-TiO2 case only.

• The exposure scenarios show the production of nano-TiO2 to be the main occupational risk.

• A moderate health effect was obtained based on relatively high exposure, but relatively low hazard.

• The variation within the occupational health risk is large due to uncertainty about exposure levels.

• Comparison of the two different ways of protecting the facade shows a substantial benefit in protecting the paint layer using the nano-TiO2 coating.

• These benefits are mainly due to the significantly lower impact in the production phase, represented by the lower consumption of coating material.

• The ensuing life stages are of almost no importance in comparison to the production stage.

Basic assumptions: The object of study is 1 m2 of wall that must be, protected for 75 years. In the conventional case, the wall is painted every 20 years using traditional paint. In the other case, the same paint is applied once, but a nano-TiO2 coating is applied on to it every 15 years. Socio-economic benefits and environmental risk assessment are not included in the in-depth analysis, therefore the risk assessment is limited to occupational risks.


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Combining Life Cycle Assessment and Risk Assessment results for decision making


Disclaimer: This case study is designed on the basis of current knowledge on nanomaterials. The development of knowledge in the field of nanomaterials is progressing fast, therefore the partners of the LICARA project cannot give guarantees as to the correctness of the information herein. New knowledge can influence the conclusions of this case study (September 2014).

From the nanoSCAN: In this case study, the results from the nanoSCAN are not clear. This is due to the moderate benefits and high occupational health risks. The overall conclusion is somewhat unclear and does not permit an easy decision-making over the strategy to adopt with this product. From the in-depth Life Cycle Assessment and Risk Assessment studies: The nanoSCAN results are somewhat confirmed. The potential impacts on human health in the nano-TiO2 coating production phase by far outweigh the benefits found in the LCA calculation, even in the minimum configuration. This shows that the production stage is the coating’s most crucial life stage. Conclusion using both analytical steps: The full assessment identifies all the relevant aspects within this system. A facade coating system based on nano-TiO2 may have an overall benefit when releases (and related exposure) of nano-TiO2 in the production stage can be limited to an amount well below the best case scenario used in this case study’s Risk Assessment calculations. What next? The company needs to monitor and minimise human exposure to releases of nano-TiO2 in the production phase. Only a low exposure to nano-TiO2 could result in a go-ahead for this nanoparticle application.

Interpretation of results Benefits: Reduction in the consumption of coating materials (nano-TiO2 coating and the underlying paint) results in environmental benefits from using the new product. Risks: The main risk results from potential impacts on human health in the coating production phase; independently of the actual exposure to nano-TiO2 releases, these impacts result in a loss of benefits in the nano-TiO2 case. Next steps: Check how exposure to nano-TiO2 can be further reduced.

Documents

Case studies on MWCNT nanosilver and nanotitanium dioxide