CO2 and Energy
Jasper Kok
Applied Physics Program
Climate science & policy enthusiast
Lecture for AOSS 480, Ricky Rood
Context: Energy and Climate Change
Carbon Emissions (GtC/yr)
10
cement and
gas flaring
8
gas
6
oil
4
coal
2
deforestation
0
1850
1900
1950
2000
Context: Energy and Climate Change
SOCIETAL SUCCESS
 Consumption // Population // Energy
ENERGY
POPULATION
CONSUMPTION
NATIONAL SECURITY
CLIMATE CHANGE
AGRICULTURE
PUBLIC HEALTH
Outline Lecture 1
 Lecture 1: Current and past energy use
– CO2 emissions: where do they come from?
– Current sources of energy
– Emissions from economic sectors
– Energy consumption by end use
– External costs to energy use (besides
climate change)
Outline Lecture 2
 Lecture 2: Future energy use and climate
change mitigation
– ‘Business as usual’
– ‘Wedges’ to mitigate climate change from
energy use
 Energy efficiency
 Renewable energies
 Carbon sequestration
 Transportation
Readings on local servers
 Assigned Reading
– Pacala and Socolow: Wedges for mitigation of climate change
(Science, 2004)
 Additional Relevant Reading
– Pacala and Socolow: Wedges for mitigation of climate change:
Supporting material (Science, 2004)
– Socolow and Pacala: Keeping Carbon in Check (Scientific American,
2006)
 Fundamental Information
– Energy Information Administration (EIA) keeps track of (inter)national
energy use and future trends.
Outline Lecture 1 Revisited
 Lecture 1: Current and past energy use
–CO2 emissions: where do
they come from?
– Current sources of energy
– Emissions from economic sectors
– Energy consumption by end use
– External costs to energy use (besides
climate change)
World Carbon Emissions
Carbon Emissions (GtC/yr)
10
cement and
gas flaring
8
gas
6
oil
75%
4
coal
2
deforestation
0
1850
1900
1950
 So CO2 emissions arise from:
1. Cement production (~5 %)
2. Deforestation (~20 %)
3. Fossil fuel use (~75 %)
2000
CO2 source: Cement Production

Cement is produced from
limestone, which is mostly calcite
(CaCO3).

For production of cement:
CaCO3  CaO + CO2

Production of cement emits CO2
for two reasons:
1. CO2 emitted directly
2. Production process takes place at
high temperatures only (> 1000 ºC)
which requires a lot of energy.

Accounts for ~5 % of CO2
emissions worldwide
CO2 source: Deforestation
 Massive deforestation occurred
– In developed nations during
Industrial Revolution (driven by
need for cheap energy)
– In developing (tropical) nations right
now, mostly in response to demand
for cropland, pastures, and wood.
 When forests are cut down, CO2
is released from:
– Carbon in trees, plants, etc.
(conversion to wood products
preserves only small fraction)
– Carbon in the soil (roots, humus)
 Forests absorb “excess” CO2,
since elevated CO2 stimulates
growth
– Removal of forests removes this
natural buffer against climate
change
CO2 source: Deforestation
Carbon Emissions (GtC/yr)
10
8
Fossil fuels
320
Deforestation
200
Total
cement and
gas flaring
gas
520 GtC
6
4
oil
Compare to 590 GtC
in the preindustrial
atmosphere
coal
2
deforestation
0
1850
1900
1950
2000
 Deforestation is thus an important part of climate change:
– It accounts for ~20 % of current CO2 emissions
– It accounted for ~35 % of total CO2 emissions since preindustrial
times.
CO2 source: Fossil Fuel Use
 Sharp increase (16-fold!) in world energy consumption
over past century
– Why did this occur?
So why has energy consumption
increased so much?
Energy use = (population)*(GDP/Person)
*(energy/unit GDP)
 GDP/capita is considered the “societal success”
 Energy use increases have been driven by
growth in population and GDP/capita.
Energy and population
 Strong population
increase since
pre-industrial
times!
http://www.j-bradford-delong.net/TCEH/1998_Draft/World_GDP/Estimating_World_GDP.html
Energy use = (population)*(GDP/Person)
*(energy/unit GDP)
World GDP/capita
 Also strong
growth in
GDP/capita!
http://www.j-bradford-delong.net/TCEH/1998_Draft/World_GDP/Estimating_World_GDP.html
Energy use = (population)*(GDP/Person)
*(energy/unit GDP)
Energy and GDP
Energy use per capita and per dollar GDP in
U.S. (index, 1980 = 1)
 Energy/unit GDP
decreases as societies
become more
developed
 shift from
manufacturing to services
(root cause of Michigan’s
economic woes)
 But total energy use
per capita does not
decrease.
EIA Annual Energy Outllok, 2008
Energy use = (population)*(GDP/Person)
*(energy/unit GDP)
So why has energy consumption
increased so much?
Energy use = (population)*(GDP/Person)*(energy/unit GDP)
 Main drivers of rapid increase in energy consumption have
been increases in population and GDP/capita
 This is why climate change problem is so difficult:
– We can’t affect population (possible, but politically incorrect…)
– Reducing GDP to combat climate change is also not feasible
 But reduction in energy per unit GDP occurs with shift to
knowledge-based economy (developed world now).
 Still, reduction in world energy use not realistic!
– To reduce CO2 emissions, need to drastically lower CO2 emitted per
unit energy, especially since we want economy to keep growing.
– We’ll get to options for reducing CO2/energy in 2nd lecture
Outline Lecture 1 Revisited
 Lecture 1: Current and past energy use
– CO2 emissions: where do they come from?
–Current sources of energy
– Emissions from economic sectors
– Energy consumption by end use
– External costs to energy use (besides
climate change)
In what forms do we
consume energy?
 Fossil fuels:
– Coal
– Oil
– Natural gas
 Other:
– Nuclear
– Hydro
– Renewables
(mostly
biomass)
– ‘Hydrogen’
Pacala and Socolow, Science, 2004
Current sources
of energy:
Fossil fuels
Energy sources: Coal
 Emits most CO2 per unit energy of all
fossil fuels
 Accounts for ~29% of world CO2
emissions
 Used mostly for electricity and for home
heating (especially in developing
nations)
 Coal burning emits significant amounts
of sulfur, nitrogen and particulate matter
 Proven reserves are almost endless
(~250 years)
Coal is major source of air pollution
 Coal emits sulfur and smoke
particulates
 “Great London smog” of 1952 led
to thousands of casualties.
– Caused by cold inversion layer
 pollutants didn’t disperse +
Londoners burned large amounts of
coal for heating
 Demonstrated impact of
pollutants and played role in
passage of “Clean Air Acts” in
the US and Western Europe
Coal use in the US
Coal use by
sector in US
EIA Annual Energy Review, 2006
 After “Great London smog” of 1952, decrease in residential coal
use
 Use of coal for electricity has been growing consistently because
coal is cheap and abundant, and combustion technology is
readily available
Energy sources: Oil
 Emits ~75 % of coal CO2 emissions per
unit energy.
 Accounts for ~30 % of world CO2
emissions.
 Dominates transportation (cars), but also
used for home/building heating
 Proven reserves are ~40 years of
conventional oil. After that, another ~100
years of unconventional oil (tar sands etc.)
 U.S. dependency on imported oil is a major
national security concern
Energy sources: Natural gas
 Least polluting of the fossil fuels:
emits ‘only’ ~60 % of coal CO2 per
unit energy
 Accounted for ~16% of world CO2
emissions
 Used for electricity generation and
home heating (same as coal)
 Proven reserves are another ~65
years
Trend of fossil fuel use
 In ‘businessas-usual’
fossil fuels will
continue to
dominate
world energy
 China
currently adds
one coal-fired
power plant a
week…
International Energy Outlook, EIA, 2007
Reserves of fossil fuels
Fuel type:
Unconventional
reserves (years)
Oil
Proven
reserves
(years)
41
Coal
251
210
Natural Gas
64
360
125
Source: World Energy Assessment, 2004
 We won’t be running out of fossil fuels anytime soon!
 ‘Unconventional’ includes oil sands, oil shale, coalbed
methane, etc..
– Unconventional fossil fuels cost more energy/effort to mine
Current sources
of energy:
nuclear and
renewables
Energy sources: Nuclear
 Accounts for ~6 % of world energy
consumption and ~ 19 % of US
electricity generation
Nuclear share of electricity
generation in U.S.
 Used only for electricity generation
 No CO2 emissions from plant
operating, but some from uranium
mining (~10 - 20 % of coal emissions
per kWh)
Nuclear power plant licenses
issued in U.S.
Chernobyl
 Concerns about nuclear waste
storage and nuclear weapons
proliferation
 Hardly growing in most of developed
world.
EIA Annual Energy Review, 2006
Energy sources: Renewables
 Mostly from
biomass (wood),
hydro power, and
biofuels.
Renewable energy as share of
total energy in U.S., 2006
 Contribution from
other renewables
(geothermal, solar,
wind, tides) are
small.
 Will discuss all
these in more detail
in 2nd lecture.
EIA Annual Energy Review, 2006
Energy ‘sources’: Hydrogen

Hydrogen as a fuel is often misunderstood:
– Hydrogen is NOT a source of energy!
– It’s merely an energy carrier, much like electricity

Hydrogen is produced by electrolyzing water:
 This requires electricity

Hydrogen burns cleanly

Hydrogen’s significance is that:
1. It can be produced using renewable energy, which
would displace fossil fuel.
2. Emissions are easier to mitigate, because they occur at
a central location rather than individual cars.

In the absence of policies including cost of climate
change, hydrogen would be generated using cheap
coal-generated electricity
Outline Lecture 1 Revisited
 Lecture 1: Current and past energy use
– CO2 emissions: where do they come from?
– Current sources of energy
–Emissions from economic
sectors
– Energy consumption by end use
– External costs to energy use (besides
climate change)
Emissions from economic sectors
 Industrial: creating
products from raw
materials (mining,
cement, agriculture)
US energy use by sector
 Commercial: stores,
municipalities, etc.
 Transportation: cars,
planes, ships
EIA Annual Energy Review, 2006
Transportation sector
 Sector with fastest
growing CO2 emissions
in US
U.S. energy consumption
by sector
 Dominated by oil and
road transport
 Accounts for ~23 % of
worldwide and ~32 % of
US CO2 emissions
EIA Annual Energy Review, 2006
Buildings sector
 Both residential and
commercial (stores,
municipalities, etc.)
U.S. energy consumption
by sector
 Mostly electricity,
except for fuel use
for space heating
 Accounts for ~39 %
of US energy use.
EIA Annual Energy Review, 2006
Industrial sector
 Includes mining,
refining, factories, etc.
 The fraction of energy
used by this sector
generally decreases as
countries become more
developed.
 Also includes
agriculture…
U.S. energy consumption
by sector
U.S. industrial energy consumption
by fuel
EIA Annual Energy Review, 2006
Agriculture
 Use of direct fossil fuel energy
relatively low: ~3–4.5 % in
industrialized countries.
– Half of used energy and direct
CO2 emissions are from fertilizer
production (Haber-Bosch
process)
 BUT… big contributor to
deforestation and land use
change.
 Livestock rearing is most
significant contributor
Agriculture: Livestock
 2006 report of Food and Agriculture
Organization (FAO) of the UN:
– “The livestock sector emerges as one of
the top two or three most significant
contributors to the most serious
environmental problems, at every scale
from local to global.”
 Important economic sector:
– Employs 1.3 billion people (mostly poor)
– Occupies 30 % (!) of Earth’s land
surface through grazing (26 %) and
feed production
 33 % of arable land for feed production
Agriculture: Livestock
 Increasing demand for livestock
products (meat, dairy) is one of
main drivers of deforestation!
– 70 % of deforested land in Amazon
is occupied by pastures.
– Feedcrops cover most of remaining
30 %.
– Livestock-induced deforestation
emits ~0.65 GtC per year (compared
to ~7 GtC from total fossil fuel use
and ~2 GtC total deforestation)
 Livestock demand increasing
rapidly with increasing world
wealth (India, China). Should
more than double by 2050.
Agriculture: Livestock
 Responsible for ~18 % of CO2
equivalent GHG emissions (so
including N2O and CH4)
 Same share as entire US!
– 9 % of world CO2 emissions
 Fossil fuels burned to produce fertilizer
 Deforestation and land use changes for
feed production and grazing (bulk!)
 Fermentation in cattle stomachs (biggest
anthropogenic source)
 Animal manure
– 65 % of N2O
 Mostly from animal manure deposited on
soils, with subsequent N2O emission
10
Carbon Emissions (GtC/yr)
– 37 % of world CH4 emissions
cement and
gas flaring
8
gas
6
oil
4
coal
2
deforestation
0
1850
1900
1950
2000
Outline Lecture 1 Revisited
 Lecture 1: Current and past energy use
– CO2 emissions: where do they come from?
– Current sources of energy
– Emissions from economic sectors
–Energy consumption by end
use
– External costs to energy use (besides
climate change)
Energy consumption by end use
 The three main end
uses of fossil fuel are:
– Electric power plants
(~40 % of CO2 emissions)
– Transportation (~23 % of
CO2 emissions)
– Direct use of fuel (industrial
processes and heating for
buildings) (~37 % of CO2
emissions)
 So ~40 % CO2 emissions
from electricity, 60 % from
fuels
World CO2 emissions
by fuel and end use
Socolow and Pacala , 2006
Energy consumption by end use:
Electricity
 Two thirds of
world electricity
production
comes from
fossil fuels
 One third from
hydro and
nuclear power
Cost of Electricity
Cost of
electricity in US
Electricity generation by source,
U.S., 2006
 Coal is cheapest and most used source of
electricity in US!
 Solar Photovoltaic (PV) rather expensive
Reserves of fossil fuels (repeat)
Fuel type:
Unconventional
reserves (years)
Oil
Proven
reserves
(years)
41
Coal
251
210
Natural Gas
64
360
125
Source: World Energy Assessment, 2004
 We won’t be running out of fossil fuels anytime soon!
 ‘Unconventional’ includes oil sands, oil shale, coalbed
methane, etc..
– Unconventional fossil fuels cost more energy/effort to mine
Electricity generation:
Switch to renewables in future?
 So in ‘business-as-usual’
abundant, cheap, fossil fuelderived electricity will likely be
available until the end of the
century.
 This cheap electricity can also
be used to produce hydrogen
fuel, should oil demand exceed
supply.
 Renewables will thus not play
important role until
– Externalities are taken into
account (taxes, cap-and-trade)
– There are technological
breakthroughs (solar PV, fusion)
Energy consumption by end use:
Fuel use
 ‘Fuel use:’
– Transportation (oil)
– Heating in buildings
– Industrial processes
 Dominated by oil
 No real alternatives for
transportation fuels
Direct Fuel Use
– Biofuels do not mitigate CO2
emission (more in 2nd
lecture)
– Future switch to renewablepowered hydrogen and/or
electric cars?
Pacala and Socolow, 2006
Outline Lecture 1 Revisited
 Lecture 1: Current and past energy use
– CO2 emissions: where do they come from?
– Current sources of energy
– Emissions from economic sectors
– Energy consumption by end use
–External costs to energy use
(besides climate change)
Energy and National Security
 U.S. imports most of its oil
US oil trade
– This is a liability, as some of that oil
comes from Middle East (though not as
much as one would think!)
– Past (and most of current) U.S. energy
policy revolves around energy security
– not climate change mitigation
 Majority of remaining oil in Middle East
Origin of US oil imports, 2006
Energy and Public Health
 The burning of fossil fuels is the dominant source of
air pollution, emitting
– Carbon monoxide (CO), which is toxic and can cause
headaches and exacerbate heart disease
– Nitrogen oxides (NOx), which causes respiratory
problems and leads to smog
– Sulfur dioxide (SO2), which produces acid rain and smog
– Particulate matter, which causes respiratory problems
– Mercury emissions, which are mostly taken in through
fish, where they bioaccumulate.
 The overall cost of air pollution on human health is
large (~6 % of deaths in EU) but very difficult to
quantify
Energy and climate (besides
greenhouse warming)
 Burning of fossil
fuels is important
source of particulate
matter (aerosols),
which helps cool
climate by:
– Scattering
radiation
– Seeding clouds
 Cleaning up ‘dirty
coal’ might thus not
be good for
climate…
To be continued….
 So what does our energy future look like?
– Can we sustain our economic growth while
avoiding ‘dangerous’ climate change?
– What roles can renewable energy, hydrogen,
biofuels, carbon sequestration play in this?
 Will discuss in more detail in 2nd lecture