Plastics and Environmental Sustainability E-Book

Anthony L. Andrady

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 639

Veröffentlichungsjahr: 2015

Beschreibung

Survey's the issues typically raised in discussions of sustainability and plastics * Discusses current issues not covered in detail previously such as ocean litter, migration of additives into food products and the recovery of plastics * Covers post-consumer fate of plastics on land and in the oceans, highlighting the environmental impacts of disposal methods * Details toxicity of plastics, particularly as it applies to human health * Presents a clear analysis of the key plastic-related issues including numerous citations of the research base that supports and contradicts the popularly held notions

Leseprobe

CONTENTS

COVER

TITLE PAGE

PREFACE

ACKNOWLEDGMENTS

LIST OF PLASTIC MATERIALS

1 THE ANTHROPOCENE

1.1 ENERGY FUTURES

1.2 MATERIALS DEMAND IN THE FUTURE

1.3 ENVIRONMENTAL POLLUTION

REFERENCES

2 A SUSTAINABILITY PRIMER

2.1 THE PRECAUTIONARY PRINCIPLE

2.2 MICROECONOMICS OF SUSTAINABILITY: THE BUSINESS ENTERPRISE

2.3 MODELS ON IMPLEMENTING SUSTAINABILITY

2.4 LIFE CYCLE ANALYSIS

2.5 THE EMERGING PARADIGM AND THE PLASTICS INDUSTRY

REFERENCES

3 AN INTRODUCTION TO PLASTICS

3.1 POLYMER MOLECULES

3.2 CONSEQUENCES OF LONG-CHAIN MOLECULAR ARCHITECTURE

3.3 SYNTHESIS OF POLYMERS

3.4 TESTING OF POLYMERS

3.5 COMMON PLASTICS

REFERENCES

4 PLASTIC PRODUCTS

4.1 PLASTICS: THE MIRACLE MATERIAL

4.2 PLASTIC PRODUCTION, USE, AND DISPOSAL

4.3 PROCESSING METHODS FOR COMMON THERMOPLASTICS

4.4 THE ENVIRONMENTAL FOOTPRINT OF PLASTICS

4.5 PLASTICS ADDITIVES

4.6 BIOPOLYMER OR BIO-DERIVED PLASTICS

REFERENCES

5 SOCIETAL BENEFITS OF PLASTICS

5.1 TRANSPORTATION APPLICATIONS OF PLASTICS

5.2 BENEFITS FROM PLASTIC PACKAGING

5.3 PLASTICS IN AGRICULTURE

5.4 BUILDING INDUSTRY APPLICATIONS

5.5 ORIGINAL EQUIPMENT MANUFACTURE (OEM)

5.6 USING PLASTICS SUSTAINABLY

REFERENCES

6 DEGRADATION OF PLASTICS IN THE ENVIRONMENT

6.1 DEFINING DEGRADABILITY

6.2 CHEMISTRY OF LIGHT-INDUCED DEGRADATION

6.3 ENHANCED PHOTODEGRADABLE POLYOLEFINS

6.4 BIODEGRADATION OF POLYMERS

6.5 BIODEGRADABILITY OF COMMON POLYMERS

REFERENCES

7 ENDOCRINE DISRUPTOR CHEMICALS

7.1 ENDOCRINE DISRUPTOR CHEMICALS USED IN PLASTICS INDUSTRY

7.2 BPA {2,2-BIS(4-HYDROXYPHENYL)PROPANE}

7.3 PHTHALATE PLASTICIZERS

7.4 POLYBROMINATED DIPHENYL ETHERS (PBDEs)

7.5 ALKYLPHENOLS AND THEIR ETHOXYLATES (APE)

7.6 EDCs AND PET BOTTLES

REFERENCES

8 PLASTICS AND HEALTH IMPACTS

8.1 PACKAGING VERSUS THE CONTENTS

8.2 PACKAGE–FOOD INTERACTIONS

8.3 STYRENE AND EXPANDED POLYSTYRENE FOOD SERVICE MATERIALS

8.4 RANKING COMMON PLASTICS

REFERENCES

9 MANAGING PLASTIC WASTE

9.1 RECOVERY OF WASTE

9.2 PYROLYSIS OF PLASTIC WASTE FOR FEEDSTOCK RECOVERY

9.3 SUSTAINABLE WASTE MANAGEMENT CHOICES

9.4 MECHANICAL RECYCLING OF PLASTICS

9.5 RECYCLING BOTTLES: BEVERAGE BOTTLES AND JUGS

9.6 DESIGNING FOR RECYCLABILITY

REFERENCES

10 PLASTICS IN THE OCEANS

10.1 ORIGINS OF PLASTICS IN THE OCEAN

10.2 WEATHERING OF PLASTICS IN THE OCEAN ENVIRONMENT

10.3 MICROPLASTIC DEBRIS

10.4 OCEAN LITTER AND SUSTAINABILITY

REFERENCES

INDEX

END USER LICENSE AGREEMENT

List of Tables

Chapter 01

Table 1.1 Approximate Global Use of Selected Building Materials (2011 Data)

Table 1.2 Estimated Future Global Supply of Some Common Metals

Table 1.3 The Use Sectors, Global Reserves, and Production of Selected Critical Materials

Table 1.4 Classification of Environmental Pollution Events

Chapter 03

Table 3.1 Glass Transition Temperature of Common Plastics

Table 3.2 Structure of Common Addition Polymers and their Applications

Table 3.3 Some Common Condensation Polymers

Table 3.4 Characteristics of Common Classes of Polyethylenes

Table 3.5 Properties of Different Grades of Polystyrene

Table 3.6 A Comparison of Properties For Polyolefins

Chapter 04

Table 4.1 Choices Available in Selecting a Polystyrene Resin in the US Market

a

Table 4.2 Commonly Used Processing Techniques for thermoplastics

Table 4.3 Commonly Used Processing Techniques for thermoset Materials

Table 4.4 Relative Energy intensity of Selected Plastic Processing Techniques

Table 4.5 Estimate of Plant Energy Distribution for Three Plastic Processes

Table 4.6 Comparison of EE Values and Carbon Emissions for Different Building Materials

Table 4.7 Energy-saving Opportunities in Plastics Processing

Table 4.8 Levels of Common Additives Used in Common Plastics

Table 4.9 Selected Examples of the Three Classes of Plastics

Table 4.10 Highest-capacity Bio-based Plastics by 2015

Chapter 05

Table 5.1 Density, Modulus, and Strength of Materials Used in Automobiles

Table 5.2 Common Plastics Components Used in Automobiles

Table 5.3 Estimate of EE and GWP (kg CO

2

) Per 1 l Package

Table 5.4 Embedded Energy, Solid Waste Generated, and GWP Per 10,000 Units of 12 oz Packages Manufactured

Table 5.5 Greenhouse Glazing Materials and their Characteristics

Table 5.6 A Comparison of Leading Materials Used in Window Frames

Table 5.7 The Thermal Conductivity and Environmental Performance Rating of Common Building insulation Materials

Table 5.8 Main Types of thermoplastics Used in Building Construction

Table 5.9 Candidate Wood Fibers for Wood–plastic Composites

Table 5.10 Main Types of Plastics Used in Equipment and Household Goods Manufacture

Chapter 06

Table 6.1 Most Damaging Range of Wavelengths in Sunlight for Common Thermoplastics

Table 6.2 Location-dependent Enhancement in Photodegradation Obtained Using ECO Copolymer in Place of LDPE Laminate of Same Thickness (Andrady et al., 1993a)

Table 6.3 Main Environments in Which Plastic Litter is Found

Table 6.4 A Listing of ASTM Test Methods Related to Degradation of Plastics

Table 6.5 Summary of Estimates of Biodegradation of Polyethylenes in Natural Environments by Weight Loss Method

Chapter 07

Table 7.1 A Summary of EDCs of Concern Relevant to Plastics and their Adverse Impacts on Human Health and on Animal Life

Table 7.2 Human Body Burden of BPA (only Studies with Sensitivity < ~0.1 Ng/g Reported)

Table 7.3 Examples of BPA Extraction by Different Liquids in Contact with Baby Bottles

Table 7.4 A Summary of Biological Effects of Exposure to BPA at Low Doses

Table 7.5 Common Phthalate Plasticizers and their Characteristics

Table 7.6 Typical Concentrations of DEHP in Water and Air

Table 7.7 A Summary of Effects of Human Exposure to Phthalates

Table 7.8 Some Examples of Nonphthalate Plasticizers For PVC

Table 7.9 The Solubility and Log

K

o/w

for Common Classes of BDEs

Table 7.10 A Summary of Effects of Human Exposure to PBDEs

Chapter 08

Table 8.1 The Embedded Energy and GWP of Selected Packaged Food Items (1 Kg Portions)

Table 8.2 Selected Barrier Properties of Common Plastic Packaging Films (25 μm Thick) Measured at 38°C

Table 8.3 Some Examples of Multilayer Films Used in Food Packaging

Table 8.4 Some Common Additives in Plastics Used for Packaging Food and Beverages

Table 8.5 Levels of Phthalates, OP, NP, BPA and DEHA (mean ± sd) in ng/L in the Different Food Packaging Items Considered in this Study

Table 8.6 Toxicity Levels of Monomers in Common Plastics

Table 8.7 Percentage of Component in Cold-pressed Orange Oil Sorbed by Different Plastics it was in Contact with for a 4-day Period

Table 8.8 Hazard Levels of Common Plastics Estimated from Monomer Characteristics

Chapter 09

Table 9.1 The Plastic Types Mostly Encountered in the MSW Stream

Table 9.2 Breakdown of Different Classes of Plastics in MSW and their Recovery

Table 9.3 Yield of Products from Pyrolysis of Mixed Plastic Waste

a

at 440°C (dehydrochlorination Step was at 300°C for 30 Min)

Table 9.4 The Main Reactions Involved in Gasification

Table 9.5 Environmental Features of Plastic Waste Management Options

Table 9.6 Selected Examples of Thermolysis of Common Plastics Yielding Monomer and Mixed Fuel Gas/liquids

Table 9.7 Average Emissions from 87 WTE Plants in the United States

Table 9.8 Calculated GHG Emissions from incineration of Different Plastic Resins

Table 9.9 Indicators of Principal Environmental Impact Categories, as Evaluated for Five Plastic Waste Management Approaches

Table 9.10 A Comparison of Energy Used, GHG Emissions, and Solid Waste Generation to Produce Virgin and Recycled Resins

Chapter 10

Table 10.1 Plastics Commonly Found in Ocean Debris

Table 10.2 Summary of Impacts on Marine Animals

Table 10.3 Degradation Agencies Available in Different Zones in the Marine Environment

Table 10.4 Summary of Results for Degradation of LDPE Control Samples, ECO Copolymer, and Metal-catalyzed Polyethylene Exposed in Air and Floating in Water at Different Locations

Table 10.5 Estimated Values of Log

K

PE/sw

, Log

K

PP/sw

, and Log

K

PS/sw

for Selected Model POPs

Table 10.6 A Summary of Selected Studies on the ingestion of Microparticles by Marine invertebrates

List of Illustrations

Chapter 01

Figure 1.1 Projected world population and population increments.

Figure 1.2 Rio Tinto (Red River) in Southwestern Spain devastated and tinted red from copper mining over several thousand years.

Figure 1.3 The ecological footprint of nations (hectares required per person) versus the per capita GDP of the nation.

Figure 1.4 Global energy use (open bars) and US energy use (filled bars) by source.

Figure 1.5 Hubbert’s original sketch of his curve on world oil production.

Figure 1.6 Sprawling solar energy complex in San Luis Valley, CO.

Figure 1.7 Comparison of the embodied energy (J/kg) and CO

2

footprint for different materials.

Figure 1.8 Estimated embodied energy (left) and carbon emissions (right) of classes of building materials globally consumed in 2011. See http://www.circularecology.com/ice-database.html.

Figure 1.9 Critical elements likely to be in short supply in the near future. The shaded boxes are those identified by the US DOE study (2010). The others are additional critical elements identified by a European Commission (2010).

Figure 1.10 Illustration of the life cycle of a product showing different steps. Residues are the externalities associated with each phase. Each phase also requires the input of energy.

Figure 1.11 Global average temperature variation and global CO

2

emissions over time.

Chapter 02

Figure 2.1 Linear flow of materials supporting an expanding consumer base.

Figure 2.2 Sustainable development depicted in simple diagrams.

Figure 2.3 Schematic illustration of the emphasis in business planning and implementation.

Figure 2.4 Production possibilities frontier with illustrative placement of business entities.

Figure 2.5 Improving the environment quality of product also increases profit.

Figure 2.6 Investment in better technology allows the choice of simultaneous gains in both goods to be secured but at a short-term cost.

Figure 2.7 Definition of “life cycle” in LCA exercises.

Figure 2.8 An example of a polygon plot summarizing LCA results on three products, based on 15 attributes.

Figure 2.9 Sustainability matrix for assessing environmental sustainability.

Figure 2.10 Downgauging of polyethylene film in plastic garbage bag applications.

Chapter 03

Figure 3.1 The polymerization reaction of ethylene yielding polyethylene.

Figure 3.2

Left

: A ball and stick model of a section of a PP chain.

Right

: An AFM image of a single polymer chain suggesting flexibility. Reprinted with permission from Kiriy et al., (2002). Copyright (2002) American Chemical Society.

Figure 3.3 Approximate simulation of a polymer chain with freely jointed chain model. The value of

r

is the end-to-end distance.

Figure 3.4

Left

: Schematic drawing of the molecular weight distribution of a polymer indicating the two averagesMn andMw.

Right

: Schematic diagram of the molecular weight distribution for polymer samples with low and high PDI.

Figure 3.5 Illustration of the stereochemistry in a vinyl polymer. Below each structural formula is an illustration of the stereochemistry with a “ball and stick model” for polypropylene.

Figure 3.6

Left

: An illustration of crystallites embedded in an amorphous polymer matrix.

Right

: Crystallites in plastic crystals imaged by AFM.

Figure 3.7 The change in elastic modulus

E

of a semicrystalline and amorphous polymers with the temperature.

Figure 3.8 Illustration of different types of copolymers. Sections of polymer chains are shown and each circle represents a repeat unit. (a) Alternating copolymer, (b) random copolymer, (c) block copolymer, and (d) branched block copolymer.

Figure 3.9 Upper: Standard dog-bone-shaped test piece used in tensile tests. Lower: Tensile deformation of a rectangular test piece. Notice shrinking of the width. Direction of strain shown by the

double-headed arrow at right

.

Figure 3.10

Left

: Change in shape of the dog-bone test piece.

Right

: Tensile stress–strain curves for glass bead-filled LDPE at different volume fractions of beads.

Figure 3.11

Left

: Basic features of a DSC instrument.

Right

: A generalized DSC tracing.

Figure 3.12 DSC tracings of two blends of atactic and isotactic PP showing the area under the melting curve. The designations indicate the weight fraction of isotactic and atactic PP in the blend.

Figure 3.13 Flow chart illustrating the manufacture of polyethylenes and polypropylenes.

Figure 3.14

Left

: An electron micrograph of a thin section of HIPS showing the rubber microdomains.

Right

: An electron micrograph of a thin section of SBR copolymer.

Chapter 04

Figure 4.1 The timeline for development of the common classes of thermoplastic polymers.

Figure 4.2 Upper: world plastic production in recent years. Lower: pie diagram of world thermoplastic resin capacity 2008.

Figure 4.3 Plastic resin production in different regions of the world.

Figure 4.4 A generalized flow diagram of the plastics industry showing the three phases of activity.

Figure 4.5 Schematic diagram of an injection molding machine showing the reciprocating screw and different heating zones.

Figure 4.6 An injection molding machine and examples of molded products.

Figure 4.7 Upper: schematic diagram of a single-screw extruder. Lower: a sheet extrusion die for plastics.

Figure 4.8 A diagram of the bottle blow molding process. 1. Heated parison. 2. Mold closing. 3. Blowing air into mold 4. Cooling and opening mold. 5. Molded bottle.

Figure 4.9 Embodied energy for selected classes of plastic resin. The top part of each bar is for manufacturing energy (including recovered energy), and the bottom part is for material energy.

Figure 4.10 Percentage energy used as raw materials (the lower segment of the bar), in manufacturing operations (middle, grey segment), and in transportation of raw materials (upper black segment) in the manufacture of different plastic resins in the United States.

Figure 4.11 Total direct environmental damage as a percentage of revenue for several selected industries.

Figure 4.12 Major classes of additives used in plastics industry.

Figure 4.13 Dependence of the modulus of PVC on plasticizer content. DODP and DIDP are types of phthalates TPU is a thermoplastic PU.

Figure 4.14 Basic pathways to derive chemical feedstocks from renewable and fossil fuel raw materials.

Figure 4.15 A comparison of fossil resources and carbon footprint of conventional plastics with PLA and PHA.

Figure 4.16 Schematic of PHA production facility illustrating the recycling of solid and water waste into sugarcane field. Source: Based on information from Nonato et al. (2001).

Figure 4.17 Schematic diagram of poly(lactic acid) manufacture from

l

-lactic acid.

Chapter 05

Figure 5.1 Fractions of different materials used in a 2011 light vehicle.

Figure 5.2 Effect of substituting plastic packaging materials with other packaging that provides the same functionality. Unfilled bars are for plastic packaging, and the filled bars are for a mix of other packaging. Life cycle energy consumption (scale on left) and life cycle GHG emissions (scale on right).

Figure 5.3 Plastic films used as mulch in agriculture.

Figure 5.4 Main uses of plastics in building applications.

Figure 5.5 A deck made of wood–plastic composites.

Chapter 06

Figure 6.1 Principal agents of plastics degradation in the environment.

Figure 6.2 Regions of the solar spectrum reaching the Earth’s surface.

Figure 6.3 The cyclic autoxidation reactions for a polyolefin RH.

Figure 6.4 Development of surface cracks on PP surfaces on exposure to a filtered xenon light source (600 W/m

2

) at 42°C and at different durations of exposure.

Figure 6.5 Action spectrum for the light-induced yellowing of mechanical pulp.

Figure 6.6 Effect of different solar radiation wavebands on the yellowness index of unstabilized Lexan polycarbonate film (0.70 mm) exposed to natural sunlight facing 26° South in Miami, FL.

Figure 6.7 Simplified schematic of the mechanism of UV stabilization by HALS. P refers to polymer chain.

Figure 6.8 Weathering of unstabilized LDPE films (

open symbols

) and enhanced photodegradable ECO copolymer (

filled symbols

) exposed outdoors in Miami, FL.

Figure 6.9 Two sets of data showing the relationship between number–average molecular weight and the percent retention of extensibility of degraded polyethylene. The upper set is for data on high-density polyethylene oxidized in oxygen at 100°C (Klemchuk and Horng, 1984). The lower set is for poly(ethylene-

co

-carbon monoxide) exposed outdoors at ambient temperature in air (Andrady et al., 1993a).

Figure 6.10 A schematic diagram of biodegradation of a solid polymer showing the two main stages of primary abiotic degradation to embrittlement followed by biodegradation of fragmented residue.

Figure 6.11 Diagram illustrating the potential enhanced biodegradability of only some bio-based plastics.

Figure 6.12 Weight loss curves for PHB and PHBV (films and pellets) incubated in tropical garden soil at two exposure sites in Russia: (a) Hoa Lac and (b) Dam Bai.

Figure 6.13 Respirometry experiment for measuring evolved CO

2

in biodegradation studies.

Figure 6.14 A biometer flask respirometer for carrying out mineralization studies. A respirometry curve for cellophane (regenerated cellulose sheet) compared to that of oak leaves.

Figure 6.15 Gas evolution data (filled symbols) plotted as percent mineralization for the biodegradation of bleached paperboard packaging material in a respirometer. Soil media (70 wt% humidity) with sewage sludge inoculum was used. Also included is a plot of the data (open symbols) as suggested by Equation 6.2.

Figure 6.16 Electron micrographs (a–c) showing the diversity of microbial flora on polyolefin debris surfaces exposed to marine environments. Micrograph (d) shows pitting around the microbes. All

scale bars

are 10 µm.

Chapter 07

Figure 7.1 Approximate mean BPA concentrations in baby bottles and canned food or beverages compared to that in plasma and the placenta (Schönfelder et al., 2002).

Figure 7.2 Examples of non-monotonic dose–response curves. Above: Effect of tumor volume in mice on the BPA levels in drinking water shows an inverted-U response. Numbers on the horizontal axis refer to µg BPA/l of drinking water available to the mice. These correspond to 0–500 pg of BPA/kg body weight. Below: Suppression of adiponectin release from human breast adipose explants by BPA and estradiol (E

2

). (Hugo et al., 2008).

Figure 7.3 Baby bottles and can liners may leach polycarbonate into food.

Figure 7.4 Modulus versus plasticizer (dioctyl phthalate) concentration for PS films. Two different techniques, indentation and strain-induced elastomer buckling instability for mechanical measurements (SIEBIMM), were used to estimate the modulus of the material. The latter technique is SIEBIMM, an optical technique for assessing the modulus of thin films of material.

Figure 7.5 Chemical structures of some common phthalates with their CAS numbers in parenthesis. DEHP, di(2-ethylhexyl) phthalate; DIDP, diisodecyl phthalate; BBP, butyl benzyl phthalate; DBP, dibutyl phthalate; DnPP, di-

n

-pentyl phthalate.

Figure 7.6 Intake of DEHP by source for an adult. Ingestion with food is by far the most important mechanism of exposure.

Chapter 08

Figure 8.1 Bottled water sales in the United States is on the increase with a per capita consumption of 29 US gallons in 2011.

Figure 8.2 The energy use and GWG emissions associated with the production of material and fabrication of containers for milk (~1 l). The first segment of bar is for material production, and the second is for manufacturing. Drawn from data in Ghenai (2012).

Figure 8.3 Summary of interactions between plastic packaging and the food or beverage contents.

Figure 8.4 Plastic pyramid originally proposed in 1998 by Van der Naald and Thorpe.

Chapter 09

Figure 9.1 The composition of the USMSW stream of 250 million tons generated in the year 2010.

Figure 9.2 Generation and recovery of the plastics in municipal solid waste stream in the United States. Source: USEPA.

Figure 9.3 A comparison of the heating value of plastics and conventional fuels.

Figure 9.4 Waste management options in United States (2010). The numbers in select boxes are for percentage of plastic waste in the MSW.

Figure 9.5 Different available recovery options for plastics waste.

Figure 9.6 Schematic representation of a pyrolysis process for plastics.

Figure 9.7 Basic recovery options available for plastics waste.

Figure 9.8 Chemolysis of poly(ethylene terephthalate) (PET) into chemical feedstock.

Figure 9.9 The general structure for PSDD, PCDF, and PCB are shown in the first row. An example of a congener derived from each of these is shown in the second row.

Figure 9.10 Relative environmental merit of different plastic waste management techniques.

Figure 9.11 The avoided energy and carbon emissions per kilogram of PET mechanically recycled. GWP (Global warming potential in CO

2

equivalents). The numbers from other LCA studies can vary slightly.

Figure 9.12 A general scheme for recycling of plastics recovered from MSW, illustrating closed- and open-loop pathways.

Figure 9.13 Recycling symbols. PETE is polyester (PET), V is vinyl plastics, and the “other” category covers all other resins.

Figure 9.14 Calculated concentration profile of the flavor compound limonene in PET derived from a postconsumer bottle of wall thickness 300 µm, containing a beverage with 1000 ppm of limonene, after 365 days of exposure at 23°C.

Figure 9.15 An illustration of open-loop recycling of PET into fiberfill.

Chapter 10

Figure 10.1

Upper:

Change in percent original tensile extensibility of polypropylene laminate exposed in air and floating in seawater at a beach location Biscayne Bay, FL.

Lower:

A floating rig used to expose plastics to surface water environment (in Miami Beach, FL).

Figure 10.2 A comparison of the rate of loss in extensibility of latex rubber balloons in Beaufort, NC (left) polypropylene tape in Biscayne Bay, FL (right) exposed outdoors in air and in sea water.

Figure 10.3 SEM images of different surface textures on plastic beach debris samples. (a) Flaking of surface, (b) vermiculite texture, (c) microfracture of surface, (d) surface pitting, (e) signs of initial degradation, (f) regions of preferential degradation, (g) horizontal notching from cracks, (h) deep cracks and fractures.

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PLASTICS AND ENVIRONMENTAL SUSTAINABILITY

ANTHONY L. ANDRADY, Ph.D

Adjunct Professor of Chemical and Biomolecular EngineeringNorth Carolina State University

Copyright © 2015 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New JerseyPublished simultaneously in Canada

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Library of Congress Cataloging-in-Publication Data:

Andrady, A. L. (Anthony L.) Plastics and environmental sustainability / Anthony L. Andrady, PhD.  pages cm Includes bibliographical references and index.

 ISBN 978-1-118-31260-5 (cloth)1. Plastics–Environmental aspects. 2. Plastics–Health aspects. 3. Plastics–Biodegradation. I. Title. TD798.A53 2015 628.4′4–dc23

    2014042233

Cover image courtesy of iStockphoto©Devonyu

This book is dedicated to my children and my grandchildren.

PREFACE

How quickly a concept is grasped, adopted, and assimilated into the general culture is indicative of how germane a human need it addresses. If that is indeed the case, the notion of sustainable development seemed to have struck a vibrant sympathetic chord with the contemporary society. Since its emergence in the 1980s, the general tenet of sustainability has gained rapid worldwide salience and broad global appeal in some form or the other. Though it is easy to identify with and even subscribe to it in general terms, the goal of sustainability and how to achieve it remain unclear. In addition to being a dictionary term, “sustainability”1 has also become a buzzword in the business world. Today’s message of sustainability reaches way beyond that of the early environmental movements of the 1960s and 1970s in that it includes an ethical component based on social justice for future generations.

With the global carrying capacity already exceeded, energy/materials shortages looming in the medium term, and the climate already compromised by anthropogenic impacts, many believe that we have arrived at decisive crossroads with no time to spare. The only way out of the quagmire is a radical change in thinking that encompasses the core values of sustainable growth. The message of sustainable growth has also reached chemical industry at large including the plastics industry. In a recent global survey of consumer packaged goods companies by DuPont in 2011, a majority (40%) of the respondents identified attaining sustainability (not costs or profits) as the leading challenge facing their industry today. Environmental movements including the call for sustainability have hitherto evolved along strict conservationist pathways over the decades that saw economic development inextricably linked with polluting externalities and tragedy of the commons. This invariably pitted business enterprise against the health of global environment. Industry was still identified a significant polluter and generator of waste. This has lead to the plethora of environmental regulations promulgated in the United States during those decades aiming to “regulate” their operations. The knee-jerk response has been greenwashing, a mere defensive stance by industry, seeking to make small visible changes to nudge existing practices and products into a form that might be construed as being sustainable.

The entrenched belief that business and technological development must necessarily adversely impact the environment remained entrenched in the 1970s and 1980s. In 1992, at the UN Conference in Rio, this notion was finally challenged and the dictum that economic development (so badly needed to eradicate world poverty) can occur alongside environmental preservation was finally proposed. But preservation means maintaining the environmental quality and services at least in its current state for the future generations to enjoy. Without a clearly articulated mechanism of how to achieve this rather dubious goal or the metrics to monitor the progress along the path to sustainability, the notion blossomed out into a popular sociopolitical ideal. Consumers appear to have accepted the notion and are demanding sustainable goods and services from the marketplace.

The allure of sustainable development is that it promises to somehow disengage the market growth from environmental damage. It frees up businesses from having to continually defend and justify their manufacturing practices to the consumer and the environmentalists who continually criticize them. Industry and trade associations still continue under this old paradigm perhaps by the force of habit but the rhetoric and dialogue with environmentalists are slowly changing. Accepting in principal that the need for a certain metamorphosis in their operation that reshuffles their priorities is a prerequisite to fruitful collaboration with environmental interests. The effort toward sustainability is one where industry, the consumer, and the regulators work together, ideally in a nonadversarial relationship. In this awkward allegiance, the business will move beyond meeting the regulatory minima or “room to operate” in terms of environmental compliance and respond positively to burgeoning “green consciousness” in their marketplace. It frees up the environmental movements to do what it does best, and facilitates stewardship of the ecosystem in collaboration with business interest, rather than be a watchdog. This is not an easy transformation in attitudes to envision. Yet it is a change that needs to be achieved to ensure not only continued growth and profitability but the very survivability of the planet and life as we know it.

The Consumer

Primarily, it is the mindset of traditional consumption that determines the demand for market goods, that needs to change. Businesses do not exist to preserve the environment; they exist to make profit for their owners. But to do so, they must meet the demands in the marketplace. With the rich supply of easily-accessible (albeit sometimes erroneous) information via the internet, interested consumers are rapidly becoming knowledgeable. The consumer demand for sustainable goods will grow rapidly, automatically driving business into sustainable modes of operation. Consumers need to be well informed and educated so that they are aware of the need and know what exactly to change.

In such a future scenario, the industry will be called upon to justify not only their economic objectives but also explicitly consider environmental (and social) objectives. This shift from the solely fiscally-driven business plans to the triple bottom-line business plan will propel the marked shift in corporate function. To be successful, the change in corporate orientation must encompass the entire value chain with free flow of communication across the traditional boundaries and interphases with suppliers, customers, and waste managers. This cannot be achieved by a few analysts embedded within a single department but requires champions that represent all aspects of the value chain.

Plastics Industry and Change

Why would a growing, robust, and profitable industry providing a unique class of material that is of great societal value want to change? The plastic industry certainly is not an inordinate energy user (such as cement production or livestock management) and does not place a significant demand on nonrenewable resources. The benefits provided by plastics justify the 4% fossil fuel raw materials and another 3–4% energy resources devoted to manufacturing it. In building applications, plastics save more energy that they use. In packaging (where the energy/material cost can be high), plastics reduce wastage and afford protection from spoilage to the packaged material with savings in healthcare costs. Plastics are a very desirable invention in general. However, the customer base and operating environment are changing rapidly; responding to the challenge posed by these changes is a good business strategy.

The plastics industry has its share of environmental issues. It is based on a linear flow of nonrenewable fossil fuel resources via useful consumer goods into the landfills. Lack of cradle-to-cradle corporate responsibility and design innovations to allow conservation of resources is responsible for this deficiency. For instance, there is not enough emphasis on design options for recovery of post-use waste. The move toward bio-based plastics, an essential component of sustainability, is too slow with not enough incentive to fully implement even what little has been achieved. Though good progress has been made, over-packaging and over-gauging are still seen across the plastics product range. While the plastics litter problem is at its root a social-behavioral issue, the industry is still held at least partially accountable. The issue of endocrine disruptors and other chemicals in plastics potentially contaminating human food still remains a controversial issue. Complaints on plastics in litter, microplastics in the ocean, endocrine disruptors in plastic products, and emissions from unsafe combustion have been highlighted in popular press as well as in research literature. Proactive stance by industry to design the next generation production systems is clearly the need of the day.

Any effort toward sustainability must reach well beyond mere greening of processes and products. Not that greening is bad (unless it is “greenwashing” which is unethical) but because it alone will not be enough to save the day. Sustainability starts at the design stage. Visionaries in the industry need to reassess the supply of energy, materials, and operational demands of the products. Can the present products still remain competitive, profitable, and acceptable despite perhaps more stringent regulatory scrutiny in a future world? What are the ways to increase the efficiency of energy use, materials use, and processes for the leading products? What potential health hazards (perceived as well as real) can the product pose? What technologies are missing that need to be adapted to achieve sustainability? Sustainable growth is a process (not a goal) that has a high level of uncertainty as we are planning for the present as well as for a clouded undefined future. This uncertainty has forced it to be grounded on precautionary strategies.

This Volume

This work is an attempt to survey the issues typically raised in discussions of sustainability and plastics. The author has attempted to separate scientific fact from overstatement and bias in popular discussions on the topics, based on research literature. Strong minority claims have also been presented. Understandably, there are those where plastics have been unfairly portrayed in the media and those where sections of the industry in aggressively protecting their domain have understated the adverse environmental impacts of plastics. The author has attempted to remain neutral in this exercise and he was not funded either by the plastics industry or by any environmental organization in writing this volume.

A work of this nature can never expect to satisfy all stakeholders on all topics covered. Depending on his or her affiliation, the reader will either feel environmental impacts of plastics are exaggerated or that they are too conservatively portrayed and do not capture their full adverse impact. Despite this anticipated criticism, a discussion of the science behind personal judgments and public policy is critical to the cause of sustainability. If the work serves as a catalyst for engagement between industrial and environmental interests or at least generates enough interest in either party to dig deeper into the science behind the claims, the author’s objective would have been served.

ANTHONY L. ANDRADY

Raleigh, NC2014

We did not inherit the Earth from our fathers; we merely borrowed it from our children.

Note

1

The word is derived from the Latin root

sustinere

, which means to uphold.

ACKNOWLEDGMENTS

I would like to acknowledge the help and support of many people in preparing this manuscript. Without their help and encouragement, the book would have not been possible. Special thanks to the many scientists who read through parts of the manuscript or offered helpful suggestions on the content. These include Professor Michelle A. Mendez (Department of Nutrition), University of North Carolina at Chapel Hill, Chapel Hill, NC; Professor Braden Allenby (School of Sustainable Engineering), Arizona State University, Tempe, AZ; Professor Linda Zettler (The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution), Woods Hole, MA; Professor Kara Lavendar Law (Sea Education Association), Falthom, MA; Professor Halim Hamid (University of Petroleum and Minerals), Dhahran, Saudi Arabia; Professors Saad Khan (Chemical and Biomolecular Engineering); Richard A. Venditti (Pulp and Paper Science); Steven Sexton (Agricultural and Resource Economics) all of NCSU, Raleigh, NC; and Ted Siegler (DSM Environmental Services, Inc.), Windsor, VT.

I would especially like to thank my wife Lalitha Andrady who did not complain of my many solitary long hours at the laptop preparing this manuscript!

LIST OF PLASTIC MATERIALS

LDPE—

Low density polyethylene

HDPE—

High density polyethylene

PP—

Polypropylene

PS—

Polystyrene

PVC—

Poly(vinyl chloride)

CPVC—

Chlorinated poly(vinyl chloride)

PB—

Polybutene

GPPS—

General purpose polystyrene

HIPS—

High impact polystyrene

EPS—

Expendable polystyrene

PMMA—

Poly(methyl methacrylate)

PET—

Poly(ethylene terephthalate)

PBT—

Poly(butylene terephthalate)

PC—

Polycarbonate

PA—

Polyamide

PA-6—

Polyamide 6

PA-66—

Nylon 66 or polyamide 66

CA—

Cellulose acetate

EVA—

(Ethylene-vinyl acetate) copolymer

SAN—

(Styrene-acrylonitrile) copolymer

ABS—

(Acrylonitrile-butadiene-styrene) copolymer

SBS—

(Styrene-butadiene-styrene) copolymer

1THE ANTHROPOCENE

We, the Homo sapiens sapiens, have enjoyed a relatively short but illustrious history of about 100,000 years on Earth, adapting remarkably well to its diverse range of geographical conditions and proliferating at an impressive pace across the globe. Easily displacing the competing relatives of the genus, we emerged the sole human species to claim the planet. It is a commendable feat indeed, considering the relatively low fertility and the high incidence of reproductive failures in humans compared to other mammals. A good metric of this success is the current world population that has increased exponentially over the decades and now standing at slightly over seven billion. It is estimated to grow to about 10 billion by 2100, given the increasing longevity worldwide. At this growth rate, the number of people added to the global community next year will now be equal to about the population of a small country (such as England or France) (Steck et al., 2013). The world population increased1 by 26% just in the past two decades! The plethora of environmental issues we face today and the more severe ones yet to be encountered tomorrow are a direct consequence of this dominant human monoculture striving to survive on a limited base of resources on the planet. As we approach the carrying capacity2 of the planet, competition for space and scarce resources, as well as rampant pollution, will increase to unmanageable levels, unless the human race carefully plans for its future.3 However, no global planning strategies have been agreed upon even at this late hour when irrefutable evidence of anthropogenic climate change, deforestation, and ocean pollution is steadily accumulating. Incredibly, no clear agreements are there on whether the looming major environmental problems are real or imaginary.

Though it did happen on Earth, the simultaneous occurrence of the conditions that support life as we know it is a very unlikely event, and even here, it is certainly a transient phenomenon. Life on Earth exists over the brief respite (in geological timeline) thanks to a cooling trend between the cauldron of molten metal the Earth was a few billion years back and the sun-scorched inhospitable terrain will turn into a few billion years from now. Even so, life spluttered on intermittently with a series of ice ages, geological upheavals, and mysterious mass extinctions regularly taking their toll on biodiversity. The last of these that occurred some 200 million years ago wiped out over 75% of the species! The resilient barren earth fought back for tens of millions of years to repopulate and reach the present level of biodiversity. Thankfully, the conditions are again just right to sustain life on Earth, with ample liquid water, enough solar energy to allow autotrophs to spin out a food web, a stratospheric ozone layer that shields life from harmful solar UV radiation, enough CO2 to ensure a warm climate, and oxygen to keep the biota alive. We owe life on Earth to these natural cycles in complex equilibrium. However, the apparent resilience of the biosphere to human interference can often be misleading as the dire consequences of human abuse of the ecosystem might only be realized in the long term. Figure 1.1 shows the growth in world population along with 10-year population increments.

Figure 1.1 Projected world population and population increments.

Source: Published with permission from UN Population Division. Reproduced with permission from World at Six Billion. UN Populations Division. ESA/P/WP.154 1999.

Clearly, human populations have already taken liberties with the ecosystem leaving deep footprints on the pristine fabric of nature. Biodiversity, a key metric of the health of the biosphere, is in serious decline; biodiversity fell by 30% globally within the last two decades alone (WWF, 2012). The current extinction rate is two to three orders of magnitude higher than the natural or background rate typical of Earth’s history (Mace et al., 2005). Arable land for agriculture is shrinking (on a per capita basis) as more of the fertile land is urbanized.4 Millions of hectares of land are lost to erosion and degradation; each year, a land area as large as Greece is estimated to be lost to desertification. Increasing global affluence also shifts food preferences into higher levels of the food pyramid. Though Earth is a watery planet, only 3% of the water on Earth is freshwater, most of that too remains frozen in icecaps and glaciers. Freshwater is a finite critical resource, and 70% of it is used globally for agriculture to produce food. Future possible shortage of freshwater is already speculated to spark off conflicts in arid regions of Africa. Evidence of global warming is mounting, there is growing urban air pollution where most live, and the oceans are clearly increasing in acidity due to CO2 absorption. Phytoplankton and marine biota are particularly sensitive to changes in the pH of seawater (Riebesell et al., 2000), and both the ocean productivity as well as its carbon-sink function might be seriously compromised by acidification. Some have suggested this is in fact the next mass extinction since the dinosaurs’ die-off, poised to wipe out the species all over again.5 Is it too late for the human organism to revert back to a sustainable mode of living to save itself from extinction in time before the geological life of the planet ends?

A driving force behind human success as a species is innovation. Starting with Bronze Age toolmaking, humans have steadily advanced their skills to achieve engineering in outer space, building supercomputers and now have arrived at the frontier of human cloning. Human innovative zest has grown exponentially and is now at an all-time high based on the number of patents filed worldwide. Recent inventions such as the incandescent light bulb, printing press, internal combustion engine, antibiotics, stem-cell manipulation, and the microchip have radically redefined human lifestyle.

A singularly important development in recent years is the invention of the ubiquitous plastic material. It was about 60 years back when science yielded the first commodity thermoplastic material. It was an immediate and astounding success with increasing quantities of plastics manufactured each subsequent year to meet the demands of an expanding base of practical applications. There is no argument that plastics have made our lives interesting, convenient, and safe. But like any other material or technology, the use of plastics comes with a very definite price tag.

Mining anything out of the earth creates enormous amounts of waste; about 30% of waste produced globally is in fact attributed to mining for materials. In 2008, 43% of the toxic material released to the environment was due to mining (US Environmental Protection Agency, 2009). For instance, the mining waste generated in producing a ton of aluminum metal is about 10 metric tons (MT) of rock and about 3 MT of highly polluted mud. The gold in a single wedding band generates about 18 MT of such waste ore left over after cyanide leaching (Earthworks, 2004)! The complex global engine of human social and economic progress relies on a continuing supply of engineering materials that are mined out of the earth and fabricated into diverse market products. At the end of the product “life cycle” (often defined merely in terms of its unacceptable esthetics rather than its functionality), it is reclassified as waste that has to be disposed of to make room for the next batch of improved replacements. The mining of raw materials and their preprocessing, whether it be oil, metal ore, or a fuel gas, are also as a rule energy intensive operations. Air and water resources used are “commons resources” available at no cost to the miners (Fig. 1.2). With no legal ownership, the users tend to overexploit these resources (or pollute it) to maximize individual gain. Naturally, in time, the resource will be compromised.6 Externalities7 associated with mining or other industrial processes, however, are not fully reflected in what the users pay for in a given product. Often, a community, a region, or even the entire global population is left to deal with the environmental effects of the disposal of waste generated during manufacture. The use of these ever-expanding lines of products, made available in increasing quantities each year to serve a growing population, presents an enormous demand on the Earth’s resource base.

Figure 1.2 Rio Tinto (Red River) in Southwestern Spain devastated and tinted red from copper mining over several thousand years.

The notion of “ecological footprint (EF)” (Reese, 1996, 1997) illustrates the problem faced by the world at large. EF is defined as the hectares of productive land and water theoretically required to produce on a continuing basis all the resources consumed and to assimilate all the wastes produced by a person living at a given geographic location. For instance, it is around 0.8 global hectares (gha) in India and greater than 10 gha in the United States. By most estimates, the footprint of the population has already exceeded the capacity of the planet to support it. In 2008, the EF of the 6 billion people was estimated at 2.7 gha/person, already well over the global biocapacity of approximately 1.8 gha/person in the same year (Grooten, 2013)! In North America, Scandinavia, and Australia, the footprint is already much larger (5–8 gha/capita) (Fig. 1.3). The largest component of the footprint is availability of sufficient vegetation to sequester carbon emissions from burning fossil fuels.

Figure 1.3 The ecological footprint of nations (hectares required per person) versus the per capita GDP of the nation.

Source: Reproduced with permission from Granta Design, Cambridge, UK. www.grantadesign.com

Plastics, being a material largely derived from nonrenewable resources such as oil, are not immune from these same considerations. Their production, use, and disposal involve both energy costs and material costs. The process also invariably yields emissions and waste into the environment that can have local or global consequences. Plastics industry is intricately connected and embedded in the various sectors that comprise the global economy. Its growth, sustainability, and impact on the environment ultimately depend on what the future world will look like. Therefore, to better understand the impacts of the use of plastic on the environment, it is first necessary to appreciate the anthropogenic constraints that will craft and restrict the future world. The following sections will discuss these in terms of the future energy demand, the material availability, and the pollution load spawned by increasing global population and industrial productivity.

1.1 ENERGY FUTURES

Rapid growth in population accompanies an inevitable corresponding increase in the demand for food, freshwater, shelter, and energy. Supporting rapid growth of a single dominant species occupying the highest level of the food chain must invariably compromise global biodiversity. Humans naturally appropriate most of the Earth’s resources, and to exacerbate the situation, the notion of what constitutes “comfortable living” is also continually upgraded in terms of increasingly energy- and material-intensive lifestyles. Invariably, this will mean an even higher per capita demand on materials and energy, disproportionate to the anticipated increase in population. An increasing population demanding the same set of resources at progressively higher per capita levels cannot continue to survive for too long on a pool of limited resources.

Energy for the world in 2012 was mainly derived from fossil fuels: 36.1% from oil, 25.7% from natural gas, and 19.5% from coal, with 9.7% from nuclear power and about 9% from renewable resources (Fig. 1.4). The global demand is projected by the Energy Information Administration (EIA) to rise from the present 525 quads/year8 in 2010 to 820 quads/year by 2040; over half of this energy will continue to be used for transportation9 (Chow et al., 2003). Even this estimate is likely an underestimate given the rate of growth in China and the developing world. In the developing countries, residential heating/cooling demands most of the energy followed by industrial uses. The pattern is different in the developed world where transportation is often the leading sector for energy use. How will this large annual energy deficit of about over 295 quads of energy be covered in the near future? Given our singular penchant for energy, this presents a particularly vexing problem. The most pressing problem will be the huge demand for electricity, the world’s fastest growing form of high-grade energy. About 40% of our primary energy (more than half of it from fossil fuel) is spent on generating electricity in an inefficient process that captures only about half their energy content as useful electrical energy. Satisfying electricity demand in next 20 yrs will use as much energy as from bringing on line a 1000 MW power station every 3.5 days during that period (Lior, 2010).

Figure 1.4 Global energy use (open bars) and US energy use (filled bars) by source.

Source: US 2011 data based on US Energy Information Administration. Web: www.eia.gov. World 2011 data based on International Energy Agency 2012 Report, www.iea.org.

The United States was the leading consumer of energy in the world (~95 quads in 2012) until recently. Since 2008, however, China has emerged in that role with the United States in the second place. Naturally, the same ranking also holds for national carbon emissions into the atmosphere. By 2035, China alone is expected to account for 31% of the world consumption of energy (US EIA, 2010). Around 2020, India will replace China as the main driver of the global energy demand. On a per capita basis, however, the United States leads the world in energy use; 4.6% of the world population in United States consume approximately 19% of the energy, while 7% in the European Union consume 15%. While most of this (~78%) is from fossil fuels approximately 9% of the energy is from renewable sources. But in the medium term, the United States is forecasted to have ample energy and will in fact be an exporter of energy, thanks to the exploitation of natural gas reserves.

Increased reliance on conventional fossil fuel reserves appears to be the most likely medium-term strategy to address the energy deficit, assuming no dramatic technology breakthrough (such as low-temperature fusion or splitting water with solar energy) is made. But it is becoming increasingly apparent that any form of future energy needs to be far less polluting and carbon intensive relative to fossil fuel burning. If not, there is a real possibility that humankind will “run out of livable environment” long before they run out of energy sources! About 26% of the global greenhouse gas (GHG) emissions (mostly CO2) is already from energy production.

1.1.1 Fossil Fuel Energy

Fossil fuels, such as coal, oil, and natural gas, were created millions of years ago by natural geothermal processing of primitive biomass that flourished at the time. Thus, fossil fuel reserves are in essence a huge savings account of sequestered solar energy. Since the industrial revolution, we have steadily depleted this resource to support human activity, relying on it heavily for heating and generating power. About 88% of the global energy used today is still derived from fossil fuels,10 and that translates primarily into burning 87 million barrels of oil a day (bbl/d) in 2010 (estimated to rise to nearly 90 bbl/d in 2012).11

1.1.1.1 Oil

Since Edwin Drake drilled the first oil well at the Allegheny River (PA) in 1859, we have in the United States ravenously consumed the resource also importing half of our oil needs. Global reserves of oil presently stand only at about 1.3 trillion barrels, over half of it in the Middle East and Venezuela. The US oil reserves that stand only at 25 billion barrels (2010) are continuing to be very aggressively extracted at the rate of 5.5 million (bbl/d) and can therefore only last for less than a decade. Hubbert (1956)12 proposed a bell-shaped Gaussian curve (see Fig. 1.5) to model US oil production and predicted it to peak in 1970 (and ~2005 for the world). Estimating the future oil supplies is complicated as new reserves are discovered all the time, improvements are made to extraction technologies, more oils being classified as proven resources, and due to fluctuating demands for oil in the future.

Figure 1.5 Hubbert’s original sketch of his curve on world oil production.

Source: Reprinted with permission from Smith (2012).

In the United States, we likely have already reached the peak production rate for oil [or the Hubbert’s peak] and are fast reaching the same for world oil production (see Fig. 1.5); thereafter, we can expect escalating prices. As prices rise, the recovery of heavy crudes in unconventional oil sand reserves will become increasingly economical. As expected, price increases driven by scarcity may result in both the lowering of the minimum acceptable quality of product and exploitation of poor reservoirs hitherto considered unprofitable to work on. Burning lower quality oil will result in emissions with an adverse effect on the environment. Our addiction to oil in the United States is such that we have seriously considered drilling for oil in the Arctic National Wildlife Refuge off the Northern Alaskan coast, the largest protected wilderness in the United States.

However, fossil fuel will likely be in good supply in the United States in the immediate future because of aggressive policies in place to exploit shale oil and gas reserves. These include particularly the shale gas (within layers of rock) and “tight oil and gas” trapped in low-permeability rock formations. Hydraulic fracturing or “fracking” might be the only way to exploit these presently inaccessible resources. The potential for “tight oil” and “tight gas” is so high locally that within the next few years, the United States could well be the leading oil producer in the world (replacing Saudi Arabia) and soon thereafter a net energy exporter. In spite of its attractiveness, however, hydrofracking is associated with serious environmental risks. Some of these are its link to earthquakes, the relatively high water demand for the process, limitations of environmentally acceptable disposal choices for spent process wastewater, risk of groundwater contamination, and high potential for GHG release. Despite the opposition from environmental groups, fracking is gaining pace in the United States.

Thankfully, the world still has considerable coal and shale gas reserves; the United States is believed to have 261 billion tons of coal and around 827 trillion cubic feet of shale gas. The United States is presently the second largest producer of coal, and at the present rate of consumption, reserves of coal should last the United States about another 500 years. Not only can coal be burnt to derive power but can also be converted to oil via the Fischer–Tropsch chemistry. Developed in the 1920s, the Fischer–Tropsch process converts CO and H2 (called syngas) into liquid paraffin hydrocarbons using transition metal catalysts. Syngas is obtained from coal:

The paraffin produced is upgraded into fuel by hydrocracking into smaller molecules.

1.1.1.2 Coal

Already, by the mid-decade, 43% of the world’s electricity supply was derived from burning coal.13 In the United States, 21% (and globally close to 30%) of the energy consumed in 2010 was derived from coal. At some future higher level of oil prices, the use of coal to produce synthetic oil may become cost-effective, and the relevant Hubbert’s curve would have been pushed back a few years or decades into the future. Coal is a cheap direct energy source for the United States, but this reassurance of a few more centuries of fossil fuel comes with a forbidding environmental price tag. Coal plants are more polluting and less costeffective compared to state-of-the-art natural gas plants. At least 49 GW of existing coal power plants in the United States can be retired and replaced with natural gas plants or even with wind-power plants with significant cost savings as well as improved environmental emissions (UCS, 2012).

There is a good justification for closely examining large-scale coal burning, especially without capture or sequestration of CO2 as a future strategy for generating energy. Coal-fired power plant emissions include particulate matter, sulfur dioxide (SO2