Technologies Warranting Further Study
This section addresses fossil-based fuels, biomass, nanoscience, geoengineering, nuclear fission, and wave, tidal and ocean current energy. The health and environmental concerns raised are intended as guides to developing a research agenda involving the public health community, scientists and engineers.
Liquid Fuels for Transport
Liquid fuels are needed for vehicles and the U.S. uses one quarter of the world’s oil: 22 million barrels per day or approximately 10,000 gallons a second. Half is imported. Over the past decade, the price per barrel has risen over ten-fold, as it did in the 1970s, and U.S. expenses for imported oil have risen from $45 billion in 1998 to over $400 billion in 2007 (EIA 2007). As a result of the price hikes, many nations are experiencing extreme hardship, much as they did in the 1970s, and food and fuel have become security issues (Hoyos and Blas 2008).
While the benefits of the energy from fossil fuels are self-evident, oil, coal and natural gas affect human and ecosystem health, have widened social inequities and fostered international conflict. The life cycle costs include the damages from exploration, extraction, mining, refining and transport; spills and leaks disrupt forest and coastal marine habitat, and combustion causes acid rain, air pollution and climate change.
Shale Oil and Oil Sands
Extracting liquid fuel from oil (“tar”) sands and shale to extend supplies of liquid fuels past “peak oil” (King and Fritsch 2008) consumes enormous quantities of energy and water. Exploitation of the Athabasca Oil Sands fields in Alberta, Canada impacts the surrounding environment and regional water supplies that are already under pressure. The Colorado Plateau, holding the largest deposits of shale oil in the world, is already a water-poor region and is projected to become more so.
Shale oil does not contain oil. Instead, kerogen must be mined, transported and heated to 450°C (850°F), and hydrogen added to liquefy the output (Youngquist 1998). For each barrel of oil derived, 2-to-4.5 barrels of heavily-contaminated wastewater is discharged, releasing toxins and heavy metals into soils, and surface and ground water (Griffiths et al. 2006). This process emits three times as much CO2 as does the processing of conventional petroleum (Woynillowicz et al. 2005).
Biomass (e.g., dung, wood, crop residues) is used directly for cooking in developing nations. Meeting this essential energy need creates indoor air pollution and particulate levels that often reach 20 times the U.S. standards (WHO 2002). This is a major cause of respiratory disease and early mortality in women and children in developing countries.
For most of the biofuels under mass production, energy gains are questionable. With CO2 uptake by plants equal to the CO2 emitted during their combustion, the energy, water and material inputs outweigh the energy derived. When one considers land-use changes involved, the energy balance for first generation biofuels becomes overwhelmingly negative.
The energy balance includes that used in: 1. Growing crops; 2. Manufacturing (and dispensing) fertilizers, pesticides and herbicides (derived from oil and natural gas); 3. Running farm machinery; 4. Irrigating land; 5. Grinding and transporting crops; 6. Fermentation and distillation; 7. Processing; 8. Packaging, 9. Transport; and 10. Marketing (Pimentel and Patzek 2005). Corn, in particular, requires large amounts of fertilizers and pesticides. The amounts of fossil fuel inputs exceeding the energy derived are the following:
Soybean-to-biodiesel requires 27% more fossil energy
input than is gained.
Woody biomass: 57%.
Pimentel and Patzek 2005
“… if 100% of U.S. corn were used [for bioethanol],” explains Cornell scientist David Pimentel, “it would replace only 7% of total U.S. petroleum use.”
When the conversion of forests, peatlands, savannas and grasslands to “biofuel farms” is included, corn-to-ethanol emits nearly twice the levels of GHGs as gasoline; cellulosic ethanol derived from switchgrasses increases net emissions by 50%.
Globally, deriving a wedge from [first generation] biofuels would mean devoting one sixth of cropland to crops for ethanol (Pacala and Socolow 2004).
The yields from palm plantations are eight times greater than those from soybean; but palm trees take eight years to mature. In 2006, 85% of palm oil came from Indonesia and Malaysia, and, in 2005, Malaysia produced almost 16 million long tons [1 long ton = 2240 pounds] of crude palm oil, earning $14.1 billion in export revenues (Unmacht 2006).
But fires to clear land for palm plantations are removing rainforests and peat wetlands, destroying primate habitat, and releasing large stores of carbon and heat-trapping black soot (Ramanathan and Carmichael 2008). These emissions have catapulted Indonesia into third place, after China and the U.S., on the list of global greenhouse gas emitters.
In the U.S., soybean biodiesel refineries are fouling rivers with oily by-products containing glycerin and methanol. In 2008, the discharge from one Mississippi plant killed 25,000 fish and eliminated the population of an endangered species of mussels (Goodman 2008).
Land Use Changes
In Brazil, sugar plantations have begun to push soybean plantations deeper into the Amazon. In the U.S. in 2007, increased corn acreage led to a 19% drop in soybean acreage, boosting prices for this food and feed staple (Bradsher 2008). Higher crop prices, in turn, increase forest- and grassland-clearing to grow the food and feed.
The pressures on land stem from: 1. The rising costs of fuel; 2. Persistent drought in food-growing regions; 3. Industrial zones displacing (and contaminating) cropland; 4. The growing demand for meat; 5. Depletion of soils and water; and 6. Dwindling fisheries. The quest for biofuels unleashed the current wave of escalating costs.
In January 2007, subsidized U.S. corn-for-ethanol sent residents of Mexico City, heavy consumers of corn tortillas, into the streets. According to the U.N. Food and Agricultural Organization and the World Bank, 36 nations are experiencing food insecurity. In the past year and a half food riots have occurred in Egypt, Haiti, Indonesia, Guinea, Mauritania, Mexico, Morocco, Pakistan, Senegal, Uzbekistan and Yemen, while Asian countries have erected quotas or bans on exports and instituted price controls (Bradsher 2008).
Alternative and Second Generation Biofuels
Using switchgrass to produce “cellulosic” ethanol (with enzymes produced by microbes to break down cell walls) is proposed as an alternative to using those displacing food crops. Some argue that 40 million acres of abandoned farmland and 20-30 million acres of idle lands, roadway edges and powerline rights-of-way could be restored to forest or high-diversity prairie, which could provide relatively low carbon biofuel; leaving lakes, rivers, ground water and wildlife habitat cleaner and healthier (D. Tilman, pers. comm. 2008).
On the other hand, only a small percentage of U.S. prairie grasslands remain intact and are still diverse: an acre often contains about 100 different species of native grasses, legumes, and other flowering perennials. Monocrops of switchgrass would diminish biodiversity (altering soils and increasing vulnerability to pests and blights), and harvesting would compete with other uses of the grasses, including the grazing (and overgrazing) of 100 million head of cattle, 7 million sheep and 4 million horses.
Introducing genetically modified grasses to facilitate the breakdown of cellulose and lignin into ethanol adds more layers of ecological uncertainty (Wolfenberger and Phifer 2000), for genetically modified organisms are neither permanently stable nor containable.
Farm waste, landfill methane, landfill garbage gasification, cooking grease and wood pellets do not displace food, feed or fiber crops.
Algae and Weeds
Algae grown in waste water ponds draws down atmospheric CO2 (or that emitted from a power plant) and can be converted to biodiesel; and with the residues refined into ethanol. The biomass yields are on the order of 100 times those for a field of crops. Some companies have surpassed the 15,000 gallon per acre accepted benchmark, and one company claims to produce 180,000 gallons of biodiesel a year from each acre of algae, equaling 4,000 barrels at $25 per barrel or $.59 per gallon. The next leading feedstock -- palm oil -- yeilds 635 gallons per acre per year (Siegel 2008).
Invasive weeds, such as kudzu and jatropha (a roadside African weed that is highly toxic to humans and livestock), can generate biofuels and have obvious co-benefits; though there is concern for further inadvertent spread. The U.S. Food and Drug Administration is studying the use of kudzu to generate ethanol (L. Ziska, pers. comm. 2008).
Health and Environmental Concerns
But burning all organic matter produces CO2. In addition, burning ethanol and methanol emits fine particles and volatile organic compounds, including acetaldehyde and formaldehyde, precursors of ground-level ozone or photochemical smog.
|Climate Change and Crop Security|
Worldwide, some 42% of growing and stored crops
(worth approximately $300 billion) are lost annually
due to pests, pathogens and weeds (Rosenzweig et
Warmer winters, more extreme weather events, and
changes in the timing and intensity of precipitation will
Warming and extremes are conducive to pest and
pathogen invasions: warming allows the overwintering
of insect pests and expands their potential range,
while floods foster fungi (the primary affliction of
crops), and droughts encourage aphids, whiteflies and
Rodent populations can ‘explode’ when heavy rains,
following droughts, drive them from their burrows and
provide them with fresh food sources.
CO2 stimulates the growth of agricultural weeds.
Changes in carbon to nitrogen (C:N) ratios encourage
leaf-eating pests to consume more biomass to obtain
the nitrogen they need to grow.
Increased pests, pathogens and weeds, in turn, will
require greater use of insecticides, fungicides and
herbicides, the residues of which can be carcinogenic,
neurotoxic, and harmful to reproductive health.
Warming and more weather extremes, plus more
pests, pathogens and weeds, can have “non-linear”
effects on agricultural yields (i.e., widespread loss).
There are implications for biofuel and food security,
thus human health and political stability.
Additionally, burning alcohol/gasoline mixtures releases aromatics, including polycyclic aromatic hydrocarbons (PAHs). Combustion of biodiesel also emits aromatics, and more NOxs and particulates than does the burning of gasoline.
Ozone, that increases during heat waves, damages lung tissue, can trigger and initiate cases of childhood asthma, and is a local heat-trapping gas, which enhances the urban heat island effect. The production of VOCs, particulates, oxides of nitrogen, and aromatics from ethanol/gasoline mixtures and biodiesels must be adequately assessed by public health researchers. Another concern is the health impacts of intensified farming. The consequences of monocultures include:
1. Nitrogen-containing fertilizer run-off, associated with harmful algal blooms and “dead zones” (at its peak, the Gulf of Mexico dead zone spans over 8,000 square miles, about the size of the state of New Jersey (Roach 2005)); 2. Nitrogen-contamination of groundwater (Townsend et al. 2003); 3. Depletion of groundwater (especially from sugar plantations); 4. Decreased soil fertility and nutritional quality of produce; and 5. Displacement of food crops and subsequent deforestation.
An additional concern is the health of agricultural systems associated with a changing climate.
Expropriating biological productivity on the earth’s surface to derive power may be no more sustainable than extracting and burning fossil fuels.
Coal with CO2 Capture and Storage
Coal accounts for 25% of global energy consumption, but generates 39% of the CO2 emissions. Coal burning produces one and a half times the CO2 emissions as does oil and twice that from burning natural gas (for an equal amount of energy produced). Coal consumption has grown 30% since 2002, twice as fast as any other energy source. Two-thirds of this is “steam coal,” used to produce electricity; one-third is “coking coal,” used primarily for making steel and concrete. Converting coal-to-liquid produces high levels of CO2 emissions (Krauss 2008).
The total recoverable reserves of coal worldwide are estimated at approximately 1 trillion short tons [1 short ton = 2,000 lbs] (EIA 2007). Two-thirds of this is found in four countries: U.S. 27%; Russia 17%; China 13% and India 10%. With 268 billion tons underground, the coal industry estimates the U.S. has enough to last 200 years (at current consumption levels). Coal is mined in 27 states in the U.S. and coal-fired plants provide just over 50% of the electricity.
China, however, is the chief consumer of coal, burning more than the U.S., the European Union and Japan combined.
With worldwide demand and oil insecurity growing, the price of coal doubled (from March 2007 to March 2008): from $41 to $85 per ton (Krauss 2008). By 2050, the coal industry projects that U.S. demands will double from the current 1.13 billion short tons (2005). Land and transport would be further stressed: the bulk of new mining would come from mountain-top removal and, today, 70% of U.S. rail traffic is devoted to the transport of coal.
Health and Environmental Concerns
|Coal Life Cycle Hazards|
In the 1990s over 15,000 former U.S. miners died
from coal workers’ pneumoconiosis (black lung disease)
Accidents and fatalities: 3,800 - 6,000 deaths
annually in China (Yardley 2008)
Strip mining/mountain top removal
Less expensive than underground mining; one plant
can produce 200 tons of coal/day
The impacts include:
Water contamination with carcinogens and heavy
metals associated with cancer clusters
Coal waste disposal and slurry impoundments
Burning coal with CO2 capture and storage (CCS) in terrestrial sites, and in the ocean or in deep ocean sediments (House et al. 2006), are proposed methods of deriving “clean coal.” But significant obstacles lie in the way, including the energy penalty of 40% (i.e., theadditional energy required beyond that needed for traditional coal-fired plants). The life cycle costs include: 1. The impacts of mining accidents, chronic illness, death and disability; 2. Mercury, NOxs and particulate emissions; 3. Mountain-top removal; and 4. The effects of storing large amounts of CO2.
Coal-burning releases particulates, nitrates, sulfates and, in the U.S. alone, approximately 48 tons of the neurotoxin mercury each year (EPA 2004). Fine particle pollution from U.S. power plants, principally coal plants, cuts short the lives of nearly 24,000 people each year, including 2,800 from lung cancer. It is responsible for 38,200 non-fatal heart attacks and tens of thousands of emergency room visits, hospitalizations, and lost work days (ABT 2004). Pollution from coal-fired plants in the U.S. Northeast is linked to over 43,000 asthma attacks, 300,000 episodes of upper respiratory illness, and 100 premature deaths annually (Levy and Spengler 2000; HEI 2007). The risk of death for people living within 30 miles of coal-fired plants is three-to-four times that of people living at a distance.
Additional energy penalties would accrue from filtering and storing all these pollutants.
|CO2 Capture and Storage|
A Special IPCC Report on Carbon Dioxide Capture and
Storage (Metz et al. 2005) lists the following concerns
for CCS in underground terrestrial sites:
Storing CO2 underground can acidify saline aquifers
and can leach heavy metals, such as arsenic and
lead, into ground water.
Increased pressures may cause leaks and releases
from previously drilled (often unmapped) pathways.
Large amounts of concentrated CO2 are toxic to plants
and animals.The 2006 Mammoth Mountain,
California release left dead stands of trees (KNBC
Microbial communities may be altered, with release of
Acidification increases fluid-rock interactions that
enhance calcite dissolution and solubility, and can
lead to fractures in limestone (CaCO3) and subsequent
releases of CO2 in high concentrations (Renard et al.
The safety (and insurability) of storing the billion tons of CO2 generated each year into the foreseeable future, is unknown; though storing CO2 in liquid and solid forms may reduce the hazards. But all local experiments must be assessed cautiously, for scaling up CCS to the volumes needed to generate a wedge could have unforeseen consequences.
On August 12, 1986, at 9:30 PM, a cloudy mist of naturally occurring CO2 rose suddenly from Lake Nyos, Cameroon, sweeping into adjacent valleys, killing 1,700 people, thousands of cattle, and birds and wild animals (Kling et al. 2005).
Changing Priorities and Shifting Assets
In February, 2008 the U.S. Department of Energy withdrew from the FutureGen CCS project in Matoon, Ill., involving an alliance of over a dozen fossil fuel companies, due to escalating cost projections. With European plans for coal and CCS also on hold, Norway’s pilot to bury CO2 from natural gas exploration is the lone large-scale experiment.
In the U.S., several state governors and environmental groups led major banks (JPMorgan Chase, Citigroup, Morgan Stanly and Bank of America, followers of the Carbon Principles) to reassess risks and withdraw project financing for coal-fired utility plants in favor of gas-fired plants; siting health, environmental and economic concerns (Ball 2008). In 2007, over 50 proposed coal-fired plants were delayed or canceled due to concerns over GHG emissions (Krauss 2008).
Geoengineering Climate Stability
Iron released into the sea stimulates algae to proliferate and (via photosynthesis) draw down CO2. Priming this “ocean biological pump” with iron filings is proposed as a means to: 1. Earn carbon credits; and 2. Help stabilize the climate.
Experiments to-date, however, measure CO2 that drops below the upper layers of the ocean (the photic zone down to 600 feet in the open ocean). Whether long-term storage can be achieved is unknown, and the risks of these experiments include 1. Greater ocean acidification; 2. More harmful algal blooms; and 3. Chemical reduction of some gases to strong heat-trapping gases, such as methane and nitrous oxide.
CO2 uptake has already dropped ocean pH 30% below pre-industrial levels (Caldeira and Wickett 2003; Orr et al. 2005; Lovejoy 2008), threatening shell fish (thus food webs) and coral reefs, via calcium depletion. This “osteoporosis” retards growth of organisms and may reduce the capacity of coral to rebound from warming-induced bleaching.
Other proposed geoengineering methods include: 1. Sending mirrors into space; 2. Seeding clouds; and 3. Repeatedly injecting massive amounts of sulfur into the stratosphere to reflect incoming sunlight.
Sulfates, however, remain in the atmosphere for days, while the residence time for CO2 is approximately 100 years. This measure could also delay recovery of the Antarctic ozone hole 30 to 70 years (Tilmes et al. 2008).
Nuclear fission is a non carbon-based method for generating power. The highest concentrations of nuclear power plants (each on the order of 0.5 to 1 GW) are in the U.S., Europe and Japan. Deriving a wedgefrom nuclear energy would require adding 700 GW of nuclear power or about twice that currently deployed (Pacala and Socolow 2004).
Meanwhile, mining, transport, milling, construction of facilities and disposal of fissile material all require large inputs of energy that are presently carbon-based. Additionally, there are significant health, safety, storage and security concerns, as well as the issues of costs and timing.
Uranium oxide is yellow; thus the life cycle, from mining to use and disposal, is known as the “Yellow Cake Road.” Well-documented health hazards are associated with all stages. Uranium miners experience increased lung cancer rates from radon exposure; nuclear fuel processors have increased death rates from leukemia; workers in nuclear power facilities and nuclear weapons facilities have increased mortality from all cancers (lung, multiple myeloma, and others); and communities adjacent to nuclear facilities in the U.S. and U.K. have increased rates of leukemia and other childhood cancers (Cragle et al. 1988; Morris and Knorr 1996; Beral et al. 1993; Pobel and Viel 1997; Cardis et al. 2007).
Advanced “pebble” technologies eliminate the risk of runaway fission reactions. But hazards remain. The 6.8 magnitude earthquake striking the Kashiwazaki, Japan nuclear plant, the largest in the world, in July 2007, released radiation into the sea (NIRS 2007). The public can also be exposed via accidents during transport of radioactive materials. Climate change poses additional risks from heat waves (cooling water) and accelerated sea level rise for nuclear plants near the coast, including all 13 in the U.K. Storms and weather volatility present additional threats to overly centralized power systems.
A nuclear reactor generates about 20 tons of radioactive waste annually (Wald 2008a). In the U.S., the waste is in temporary storage at 122 sites in 39 states. If a long-term repository is opened, it would take decades to clear the backlog.
Securing safe, long-term storage presents the greatest hurdle. By 2017, the date projected for opening the Yucca Mountain, Nevada site, U.S. taxpayers will have spent tens of billions of dollars (estimates run to $54 billion) to study, prepare and operate the site (Loux 1998). The 1982 National Waste Policy Act, as amended in 1987, limits the quantity of spent fuel that can be placed in the first repository to 70,000 metric tonnes [1 tonne = 2,200 pounds] of heavy metal … “until such time as a second repository is in operation" (Peterson 2003). The U.S. Geological Survey (USGS) reports 10 known faults within a 20-mile radius of Yucca Mountain. Solitario Canyon, west of the planned site, could generate a 6.5 magnitude earthquake.
On May 21, 2007 the USGS reported finding a previously undetected fault running through Yucca Mountain (AP 2007).
Meeting a wedge with nuclear energy would generate a volume of radioactive waste that would fill one “Yucca Mountain” every 5-10 years until mid-century (Keystone 2007). The larger number is based on the Congressional Bill proposing to double the amount of stored material allowed. Neither number includes burying decommissioned plants.
Regulatory criteria for Yucca Mountain require, among other things, that the groundwater below the Armagosa Valley near Yucca Mountain be protected for at least 10,000 years (Peterson 2003). Ensuring the safe storage of radioactive waste for tens-to-hundreds of thousands of years remains a serious obstacle to expanding nuclear energy.
|Relative Costs for Construction of Power Plants|
(500 MW to 1 GW)
|Cost Overruns are Common in the Nuclear Industry |
|Nuclear: $6-$12 billion||The estimated cost of the U.S. Department of Energy’s|
Supercolliding Super Conductor project in Texas rose
from $5.9 billion (late 1980s) to $11 billion (when it
was canceled in 1993).
|Coal-fired plant: ~$2 billion|
|Gas-fired plant: ~$1.6 billion (requires less steel, concrete|
and labor than coal-fired plants.)
|The Fuels and Materials Examination Facility at the|
Hanford site, Washington ran 39% over budget.
|Windfarm: ~$1.8 billion off-shore; < $1billion on-land||The waste vitrification plant (temporarily encasing waste|
in glass) at the U.S. Department of Energy’s Savannah
River site, South Carolina, was 62% over budget and
6.5 years behind schedule.
|Note: Nuclear fusion, the process found in stars (combining,|
not splitting, atomic elements), has not been
demonstrated to work at room temperatures or to be
controllable. It is, as yet, entirely experimental.
With international tensions high, and likely to remain so as climate change exacerbates conflicts over resources, security is a significant problem for nuclear power plants as well as for transported and temporarily-stored radioactive materials. The risks include attacks, and “loose nukes” and “dirty bombs” from stolen fissile material. “Peak uranium” presents additional concerns, for reprocessed spent radioactive material is more liable to abuse than is uranium.
The security issues above are, for the most part, not amenable to international treaties, and may become decisive factors in assessing the risks of expanding nuclear fission.
Costs and Timing
Costs and timing are also significant issues, given the urgency of displacing carbon-based power generators. Nuclear power plants take 8-12 years to construct, and the projected costs of constructing a new generation nuclear power plant recently rose from $6 billion to $12 billion (Smith 2008). Considerable time and subsidies would be needed to derive a stabilization wedge from nuclear fission.
Nanotechnologies, with components measuring billionths of a meter (100,000 times thinner than a human hair), can, by increasing active surface areas, dramatically increase efficiencies and reduce costs (Carts-Powell 2006; Lenatti 2006). One solar technology based on nanocomponents (plastic polymers) promises a 75% reduction in costs; but little is known of its performance, durability and safety.
Composition matters: The emerging discipline of distilling or engineering useful technologies from naturally occurring materials and organisms holds great promise. Self-assembling peptides have been shown to promote tissue healing, while nanovesicles for drug encapsulation aid drug-delivery and nanofibers can act as scaffolds for growing new tissues (Lee et al. 2005).
The “spinach chip”: An MIT team has demonstrated a plant photosynthetic energy-harvesting molecular machine that directly converts photons into electricity (Zhang et al. 2004).
Memristor: This spring, Strukov et al. (2008) reported finding the predicted fourth type of circuitry: memristor, a contraction of ‘memory resistor’. Memristor microchips, unlike capacitors, resistors and inductors, can communicate in terms intermediate between ON and OFF (or Os and 1s). These nanocells hold the promise of extending for years ‘Moore’s Law,’ whereby computer capacity doubles every 18 months.
Health and Safety Concerns
Nanocrystallites, quantum dots and nanotubes can be carbon-coated to reduce the risks of particle release during use. And many products have been used for decades that are technically nanotechnologies. But the use of these new materials must be tempered by careful evaluation of health and safety concerns, due to their small size and ability to interact with biological and other materials.
Size matters: Nanomaterials 20 microns (millionths of a meter; composed of many nanoparticles) are similar in size to asbestos fibers, and, as indicated in a study in mice (Poland et al. 2008), could lead to tissue and genetic damage via skin and respiratory inhalation. The same study showed that smaller particles, 5 microns, do not initiate inflammation.
The insurance industry is concerned with risks that include: 1. Spills in production facilities; 2. Chronic illnesses in workers; 3. Product recalls and liability from discovery of untoward effects; and 4. Potential release from disposed products (EPA 2006; Weisner 2006; Dunphy et al. 2006; Lloyds 2007).
Private investment in nanotech reached $11.8 billion in 2006. But, of the $1 billion in the U.S. National Nanotechnology Initiative, only 0.6% ($6 million) is allocated to studying the health and environmental risks.
Wave, Current and Tidal Energy
Wave, current and tidal energy are relatively new technologies. While wave and tidal power are unlikely to meet more than local needs, ocean currents offer enormous potential. Estimates for the Gulf Stream off the U.S. Southeast are 30-50 GW of zero-carbon base-load power (W. Kempton, pers. comm. 2008). It will be crucial to choose appropriate areas to pilot these technologies and to monitor physical properties, fisheries, reptile and marine mammal migration, and shipping safety.
This is a chapter from Healthy Solutions for the Low Carbon Economy: Guidelines for Investors, Insurers and Policy Makers (e-book).
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