Module 1. Introduction to Green Manufacturing and Environmental Issues

Transcription

1 Module 1. Introduction to Green Manufacturing and Environmental Issues NSF Summer Institute on Nano Mechanics and Materials: A Short Course on Nanotechnology, Biotechnology, and Green Manufacturing for Creating Sustainable Technologies June 20-24, 2005 David R. Shonnard Associate Professor Department of Chemical Engineering 1 Module 1 Outline Green Engineering/Green Manufacturing: Expanding the Box on the Analysis of Chemical Processes and Products Overview of Environmental Issues (chapter 1) Risk Concepts and Risk Assessment (ch. 4) 2

2 What is Green Engineering? Design, commercialization and use of processes and products that are feasible and economical while minimizing: Risk to human health and the environment Generation of pollution at the source US EPA, OPPT, Chemical Engineering Branch, Green Engineering Program 3 Disclaimer This short course provides insights on how to design chemical processes and products to achieve reduced environmental impacts. Concepts are applicable to other engineering and science disciplines 4

3 The Box Concept: at the Microscale Catalyst Pellet n Ax x z n Ax x+ x System Boundary x y ρ t A = n A + r A Continuity Equation for Species A 5 The Box Concept: at the Mesoscale Q Packed-Bed Reactor F in, ρ Ain, T in F out, ρ Aout, T out System Boundary n Ax x z n Ax x+ x x y 6

4 The Box Concept: at the Macroscale Energy Inputs Chemical Process System Boundary F 1 P 1 Economic Performance P 2 P 3 Emissions, Wastes Environmental Impacts P 4 7 The Box Concept: Exchanges Within/Between Facilities Energy And Mass Inputs P 1 P 2 P 3 P 1 P 2 P 3 System Boundary P 4 P 4 P 1 P 1 P 2 P 3 P 4 P 2 P 3 P 4 Products Environmental Impacts Economic Performance Societal Effects 8

5 The Box Concept: Beyond the Plant Boundary Life- Cycle Assessment System Boundary Materials Materials Materials Materials Energy Energy Energy Energy Raw Materials Extraction Chemical Processing Product Manufacturing Use, Reuse, Disposal Wastes Pollution Control Wastes Wastes Pollution Control Wastes Environmental Impacts Economic Performance Societal Effects 9 Objective/Outcomes of Short Course Objective Disseminate best methods and practices in Green Engineering and Life Cycle Assessment Learning Outcomes Learn methods to assess and improve environmental performance of processes and products Become knowledgeable of computer aided tools for impact assessment of processes and products 10

6 2-minute discussion What are the most important issues for you? Consider this and discuss with your neighbor. Be prepared to discuss why. How does your research address environmental issues? 11 U.S. Energy Flows, 2002 Values are in quadrillion (10 15 ) BTUs ( British Thermal Units) Annual Energy Review 2002, U.S. DOE, Energy Information Administration, Washington, DC, DOE/EIA-0384(2002) 12

7 US Energy Flows: Outputs U.S. Energy Flows, 2002 Values are in quadrillion (10 15 ) BTUs ( British Thermal Units) Annual Energy Review 2002, U.S. DOE, Energy Information Administration, Washington, DC, DOE/EIA-0384(2002) 13 U.S. energy overview Annual Energy Review 2002, U.S. DOE, Energy Information Administration, Washington, DC, DOE/EIA-0384(2002) 14

8 U.S. industry manufacturing energy use SIC Code BTUs/yr 29 Petroleum/Coal Products Chemicals / Allied Products Paper Primary Metals Industries Food / Beverages Nonmetallic Mineral Products Wood Products 0.51 Numbers represent roughly the % of US annual energy consumption Annual Energy Review 2002, U.S. DOE, Energy Information Administration, Washington, DC, DOE/EIA-0384(2002) 15 Global carbon flows and fuels use 6 Fossil Fuel Use Warm Surface Waters ** ** Deforestation Atmosphere Land Biota 560 Soil and Detritus 1, Numbers are in gigatons C or gigatons C/yr. Cool Surface Waters 300 Intermediate and Deep Waters 38,000 from Environmental Modeling, J.L. Schnoor, Wiley, Ocean Bottom 16

9 CO 2 and temperature in the northern hemisphere National Geographic, September 2004, pg 20, National Geographic Society, Washington, D.C. 17 Model Temperature Rise National Geographic, September 2004, pg 20, National Geographic Society, Washington, D.C. 18

10 Global warming and related impacts Materials Energy Products Cause and Effect Chain Chemical Processing greenhouse gas emissions CO 2, CH 4, N 2 O climate change; sea level change human mortality or life adjustments O 3 N 2 O CH 4 CO 2 CFCs Contribution to global Warming; Phipps, NPPC, Climate Change 1995, Intergovernmental Panel on Climate Change, WMO and UNEP, Cambridge University Press, Global warming potential BI = infrared radiation absorbance band intensity Appendix D in: Allen and Shonnard, Green Engineering: Environmentally Conscious Design of Chemical Processes, Prentice Hall,

11 Possible adverse effects of global warming Increased average temperatures and temperature extremes Melting of glaciers / polar ice and sea level rise Increased incidence of diseases such as malaria due to warmer temperatures Changing climate and altered weather patterns Disruption of land use due to droughts Migration of human populations Decreased life expectancy in some regions of the world 21 Potential solutions to global warming Increase energy efficiency of chemical production and electricity generation (cogeneration) Reduce fossil fuels usage (increase gas mileage for vehicles, more insulation for homes, etc.) Utilize renewable energy resources to a greater extent such as biomass, solar, hydroelectric, wind,.. Capture and sequester CO 2 from combustion gas streams Create chemicals with lower global warming potential 22

12 Stratospheric ozone depletion Materials Energy Cause and Effect Chain Products Chemical Processing ozone depleting substances CFCs, HCFCs ozone layer loss increase in uv human mortality or life adjustments ecosystem damage From Ozone FAQ - see 23 Catalytic ozone destruction 1. O 3 + +hν O O + O 2 2 O 3 3 O 2 3. O + XO X X+ + O 2 2. O 3 + +X X XO O + O 2 Principal ingredients for ozone loss: UV radiation & a free radical (e.g., X = OH, NO, Cl, Br) 24 Net: 2 O 3 + hν 3 O 2 Dr. Paul A. Newman NASA s Goddard Space Flight Center

13 Production trends of ozone depleting substances (Fig ) CFC-12 (x1000 ) CFC Stratospheric ozone depletion (cont.) Figure τ = 120 yr Slow recovery τ = tropospheric reaction half-life τ = 60 yr Faster recovery 26

14 Stratospheric ozone depletion (cont.) Figure CFC mole balance: Atmosphere response to CFC phase-out 1. Troposphere (0-10 km) is well-mixed 2. Annual CFC production is emitted to atmosphere (assumed) dy CFC dt = E CFC(t) M CFC m ATM 1 τ y CFC I.C. t =0, y CFC = y CFC,o y CFC = mole fraction of CFC in the troposphere E CFC (t) = emission rate of CFC (g/yr) = E CFCo e -at (AFEAS web site) M CFC = molecular weight of CFC (g/mole) m ATM = atmosphere content (1.5x10 20 moles) (Wallace/Hobbs, 1977, pg6) τ = CFC residence time in the troposphere (yr) y CFC,o = mole fraction of CFC in 1988 (Figure 1.4-3) 28

15 CFC mole balance model prediction 600 ppt = y CFC x CFC y CRC =y CRCo e t τ + E CFCo M CFC m ATM (1 / τ a) (e at e t τ ) CFC CFC-11. E CFCo = 3.14x10 11 g/yr, a = yr -1, M CFC = g/mole CFC-12. E CFCo = 3.93x10 11 g/yr, a = yr -1, M CFC = g/mole Year 29 Effects of chemical properties on ozone depletion (Chapter 5) Summary of Environmental Properties/Behavior CFCs, HCFCs, Halons partition to atmosphere nearly 100% Water solubility (v. low), Sorption to natural organic matter (v. low), vapor pressure and Henry s constant (v. high) Persistence in the atmosphere is v. high (v. small hydroxyl radical ( OH) rate constant) Reactivity increases with addition of Hydrogen to molecule, e.g. HCFCs 30

16 Ozone Depletion Potential Appendix D in: Allen and Shonnard, Green Engineering: Environmentally Conscious Design of Chemical Processes, Prentice Hall, Smog formation and related impacts Materials Energy Products Cause and Effect Chain Chemical Processing NOx and volatile organic substances photochemical oxidation reactions human/ecological damage from O 3 and other oxidants NOx VOCs 1 - Chemical & Allied Processing 2 - Petroleum & Related Industries NOx 1997 Miscellaneous 4 3 Transportation 3 - Metals Processing, 4 - Other Industrial Processes 5 - Solvent Utilization, 6 - Storage & Transportation 7 - Waste Disposal & Recycling Industrial Processes Fuel Combustion VOCs National Air Quality and Emissions Trends Report, 1997, U.S. EPA Office of Air Quality Planning and Standards, 32

17 Smog formation potential Appendix D in: Allen and Shonnard, Green Engineering: Environmentally Conscious Design of Chemical Processes, Prentice Hall, Acid rain / Acid deposition Materials Energy Products Cause and Effect Chain Chemical Processing SO 2 and NOx emission to air Acidification rxns. & acid deposition human/ecological damage from H + and heavy metals SO 2 Transportation Miscellaneous Industrial Processes Chemical & Allied Processing 2 - Petroleum & Related Industries 3 - Metals Processing 4 - Other Industrial Processes 5 - Solvent Utilization 6 - Storage & Transportation 7 - Waste Disposal & Recycling Fuel Combustion 3 2 National Air Quality and Emissions Trends Report, 1997, U.S. EPA Office of Air Quality Planning and Standards, 34

18 Acid rain potential Appendix D in: Allen and Shonnard, Green Engineering: Environmentally Conscious Design of Chemical Processes, Prentice Hall, Human health toxicity Materials Energy Products Chemical Processing Toxic releases to air, water, and soil Transport, fate, exposure pathways & routes Human health damage; carcinogenic & non... RCRA Hazardous Waste Transportation Equipment 7% Primary Metals 8% Petroleum Refining 9% All Other Industries 16% Electronic Equipment 9% Chemical / Allied Products 51% Allen and Rosselot, 1997 EPCRA Toxic Waste Petroleum Refining 3% Paper and Allied Products 5% Plastics 3% Rubber and Miscellaneous Transportation 5% Fabricated Metals 6% All Other Industries 23% Chemical and Allied Products 27% Primary Metals 22% Electronic Equipment 6% 36

19 Ecology Concepts La Grega et al., Hazardous Waste Management, McGraw Hill 37 Ecological Impacts La Grega et al. Hazardous Waste Management McGraw Hill 38

20 Systematic risk assessment methodology National Academy of Sciences, Hazard Identification (which chemicals are important?) 2. Exposure assessment (release estimation, fate and transport, dose assessment) 3. Toxicity assessment (chemical dose - response relationships) 4. Risk Characterization (magnitude and uncertainty of risk) Result: Quantitative risk assessment (e.g. excess cancers) Atmospheric dispersion Model, C a (mg/m 3 ) Thibodeaux, L.J. 1996, Environmental Chemodynamics, John Wiley & Sons 39 Absolute risk calculation Carcinogenic Risk Example (inhalation route) Exposure Dose Dose - Response Relationship, Slope Factor (mg/(kg d)) -1 Risk i = (C a CR EF ED) SF (BW AT) CR - contact rate (m 3 air inhaled / day) EF - exposure frequency (days exposed / yr) ED - exposure duration (yr) BW - body weight (kg) AT - averaging time (number of days in a lifetime) Result: # excess cancers per 10 6 cases in the population; 10-4 to 10-6 acceptable Disadvantage: Only a single compartment is modeled / Computationally inefficient Highly uncertain prediction of risk i 40

21 Module 1 summary Green Engineering expands the box in the analysis of chemical processes and products by quantifying environmental effects Chemicals emitted to the environment have multiple effects ultimately leading to human health impacts. Risk assessment is a systematic methodology to estimate human health impacts of pollutants 41 Module 2 preview Principles of Green Engineering Green Engineering: A design approach for environmental sustainability Estimating environmental properties of pollutants Estimating fate and exposure of pollutants Estimating pollutant emissions from processes Pollution prevention: 4 examples 42