Grantee Research Project Results
2006 Progress Report: Evaluating the Impacts of Nanomanufacturing via Thermodynamic and Life Cycle Analysis
EPA Grant Number: R832532Title: Evaluating the Impacts of Nanomanufacturing via Thermodynamic and Life Cycle Analysis
Investigators: Bakshi, Bhavik R. , Lee, L. James
Institution: The Ohio State University
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2006 through December 31, 2010
Project Period Covered by this Report: January 1, 2006 through December 31,2006
Project Amount: $375,000
RFA: Exploratory Research: Nanotechnology Research Grants Investigating Environmental and Human Health Effects of Manufactured Nanomaterials: A Joint Research Solicitation - EPA, NSF, NIOSH (2005) RFA Text | Recipients Lists
Research Category: Safer Chemicals , Nanotechnology
Objective:
Objective(s) of the Research Project: Nanotechnology is a fast emerging field and is likely to be a key player in influencing future global markets. There is an urgent need to assess the broader environmental and societal implications in order to ensure a safe and sustainable nanotechnology industry. The use of a holistic approach like Life Cycle Assessment (LCA) that considers environmental impact of products or processes over their entire life cycle has been suggested by researchers to evaluate potential nanoproducts. However, LCA of nanotechnology poses several formidable challenges. These primarily include the severe lack of inventory data about nanomanufacturing processes and very little quantifiable data available on the human health and ecosystem impacts of products and byproducts of nanomanufacturing. LCA studies of potential nanotechnologies are especially important at early stages of research to evaluate the economic-environmental trade-offs among manufacturing processes and among alternative products to aid in sensible engineering decision-making. The goal of this work is to establish life cycle inventory (LCI) module and perform a traditional LCA for the synthesis of vapor grown Carbon Nanofibers (CNF). CNFs are compared with traditional materials on an equal mass basis to quantify the life cycle energy intensity and environmental burden. The results of the study so far indicate significantly higher life cycle energy requirements and higher environmental impact of CNFs as compared to traditional materials like aluminum, steel and polypropylene. Since the comparisons are performed on an equal mass basis, these results cannot be generalized for CNF based nanoproducts and quantity of their use may decide their cradle to grave impact. Specific CNF based applications need to be studied to evaluate their environmental performance and are the topics of future work.
Approach:
Through collaboration with leading academic groups, industry, and a national laboratory, life cycle inventory data and modules will be developed for the synthesis and use of nanoclays and carbon nanofibres. These modules will be combined with life cycle information at different spatial scales, ranging from equipment to ecosystems, and used to perform multiscale or hybrid LCA of several potential products. Different scenarios for the manufacture, use, end of life, emissions and exposure of typical consumable and durable products, such as automotive body panels and food wrapping film, will be analyzed along with estimates of uncertainty. Thermodynamic LCA will treat industrial and ecological systems as networks of energy flow and combine the features of systems ecology, LCA and systems engineering. The proposed hypotheses will be tested in a statistical sound manner via several case studies.
Progress Summary:
Progress Summary/Accomplishments: Carbon nanofibers (CNFs) belong to a new class of materials that have exceptional mechanical and electrical properties. These properties of CNFs are being explored in a variety of ways by imparting functionalities in various intermediate and final valueadded consumer products. Applications include the use of CNFs as polymer additives for high strength polymer nanocomposites, use of CNFs in carbon-lithium batteries, start capacitors for electronic devices and electrically conducting polymers. In this study, vapor grown carbon nanofiber (VGCNF) synthesis from hydrocarbons is considered. VGCNFs are produced by high temperature catalytic pyrolysis of hydrocarbons in the presence of a transition metal acting as the catalyst. Life cycle inventory data is compiled with data reported in the open literature.
Life Cycle Energy Analysis. Traditional engineering approaches tend to focus on the process level details without caring about other steps in a product’s life cycle. However, focusing attention on one process without sufficient attention to others in a product’s supply chain can lead to the unintended environmental tradeoff of one problem for another. On the other hand, the use of a holistic, life cycle approach can help avert this problem. This is the underlying theme of this study. A Life Cycle Energy Analysis is done first at the process or equipment scale, the boundaries are then expanded to account for the other steps or inputs of the life cycle of these materials. Here “life cycle energy requirements” primarily refers to the cumulative fossil energy requirements for the synthesis of CNFs and does not include the contribution of ecosystem goods and services. Thus, it quantifies the non-renewable energy requirements along the supply chain of these nanoparticles.
Figure 1. Life cycle energy analysis of carbon nanofibers CNFs (a) effect of cycle time (production cycle time ranges from 1 hour to a continuous operation for 300 days), (b) energy distribution along life cycle phases.
Figure 1 presents a direct comparison of the life cycle energy requirements for CNFs based on different feedstocks with those of traditional materials namely aluminum, steel, and polypropylene. Figure 1 (a) reveals that the life cycle of CNFs is energy intensive, with the life cycle energy requirements ranging from 2,872 MJ/kg for benzene feedstock to around 10,925 MJ/kg for methane. In comparison, the life cycle energy requirements for aluminum, steel, and polypropylene are 218, 30, and 119 MJ/kg. Figure 1 (b) show breakdown of energy requirements along the CNF life cycle phases. On a per mass basis, the life cycle energy requirements for producing CNFs is 13-50 times that required for producing traditional materials (i.e., aluminum, steel, and polypropylene).
Figure 2. Vapor grown carbon nanofibers – life cycle assessment (VGCNF LCA) (a) global warming potential - midpoint indicator (b) DALYs – damage indicator.
Environmental LCA of CNFs. The next step is to perform an Environmental Life Cycle Assessment of nanoparticle synthesis. A “cradle-to-gate” Process LCA of CNF synthesis has thus been completed, and midpoint and endpoint impact assessment methods suggest that VGCNFs may impose a higher environmental burden than traditional materials per kilogram of product. This is reflected from the higher impact of CNFs in most environmental impact categories. Two base cases are evaluated for CNF synthesis, one with methane and the other with ethylene as the feedstock. Both cases are considered to have hydrogen as the carrier gas in accordance with the current industrial schemes. Fig. 2 shows the result of midpoint and impact assessment methods. Fig. 2 (a) indicates higher global warming potential (GWP) for both methane and ethylene based CNFs when compared with aluminum, steel, and polypropylene on an equal mass basis. Similar trends are observed for other midpoint impact categories. EcoIndicator 99 methodology is used to obtain damage indicators. Under Eco-indicator, only three kind of environmental damages are weighed, namely damage to human health, damage to ecosystem quality and damage to resources. Figure 2 (b) indicates the higher impact of CNFs in the category of damage to human health which is expressed in terms of DALYs (Disability Adjusted Life Years) per kilogram of product. DALYs incorporates damage to human health in the form of Years of life lost (YLL) and years of lives disabled (YLD) as a result of emissions of substances along the supply chain of a product. Similar trends are observed for the category of damage to ecosystems and damage to resource categories. It is important to reiterate that human and ecosystem impact of CNFs is not accounted due to lack of information about the human and ecotoxicological impact of these engineered nanoparticles. Detailed knowledge and quantifiable data about the fate, transport, and mechanism of damage of CNFs is not available. Thus, the impact numbers presented here reflect only the material and energy use during the synthesis of CNFs.
Expected Results:
LCA of nanotechnology is essential for guiding and managing risk in research, development and commercialization while preventing irrational optimism or unfounded fear of this emerging field. However, it presents formidable obstacles since data and knowledge about resource consumption, emissions and their impact are either unknown or not readily available. This work will lay the foundation for LCA of polymer nanocomposites and other emerging technologies. Validation of the first hypothesis will provide useful insight about nano versus traditional technologies while the second hypothesis will provide a proxy for the ecotoxicological impact of the emissions. These hypotheses will be useful for nano and other emerging technologies before detailed emissions data and ecotoxicological studies are available. As more information about manufacturing, emissions and their impact becomes available it will be incorporated in the proposed studies and tool.
Future Activities:
Life cycle energy analysis of CNF synthesis is presented and compared with traditional materials on an equal mass basis. Preliminary results indicate 13-50 times higher life cycle energy requirements for CNFs when compared with primary aluminum on an equal mass basis. High energy requirements and hence the possible high cost of these engineered nanomaterials will tend to restrict their use only in very niche applications and hinder their use for large volume applications like polymer composites. Midpoint and endpoint impact assessment methods suggest that VGCNFs may impose a higher environmental burden than traditional materials per kilogram of product. However, products based on CNFs might be greener than alternatives for a given application. Quantity of their use will be the deciding factor and hence comparisons based on functional unit i.e. specific nanoproducts and applications need to be evaluated. Future work is expected to use these results to evaluate claims about the potential benefits of specific CNF based nanoproducts. Specifically, the use of CNF based polymer nanocomposites will be studied and several end product applications based on CNF reinforced polymer composites will be studied. These studies also ignore the possible emissions and impact of nanoparticles, and thermodynamic LCA methods are also being explored as proxy indicators in the absence of emissions and impact information.
Journal Articles:
No journal articles submitted with this report: View all 19 publications for this projectSupplemental Keywords:
Life cycle assessment, nanoproducts, energy analysis, life cycle inventory, impact assessment, midpoint indicators, damage indicators.
, Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Environmental Chemistry, Risk Assessments, Environmental Microbiology, Risk Assessment, ecological risk assessment, environmental risks, carbon fullerene, nanotechnology, human exposure, nanomaterials, nanoparticulate aerosol, polymer nanocomposites, nanoparticle toxicity, exposure assessment
Relevant Websites:
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.