CO 2 and Energy #2 Jasper Kok Applied Physics Program Climate science & policy enthusiast Lecture for AOSS 480, Ricky Rood.
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CO2 and Energy #2
Jasper KokApplied Physics Program
Climate science & policy enthusiastLecture for AOSS 480, Ricky Rood
Outline and review lecture 1
Lecture 1: Current and past energy use– Historic CO2 emissions
and energy use– Current sources of
energy
– Energy use and CO2 emissions of economic sectors
– Energy use and CO2 emissions by end use
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2
4
6
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10
1850 1900 1950 2000
Car
bo
n E
mis
sio
ns
(GtC
/yr)
coal
oil
gas
deforestation
cement and gas flaring
World CO2 emissions by fuel and end use
US energy use by sector
Outline Lecture 2
Lecture 2: Future energy use and climate change mitigation– ‘Business as usual’
Do we need to act to prevent ‘dangerous anthropogenic interference’ in the climate system?
– ‘Wedges’ to mitigate climate change – Energy supply decarbonization ‘tools’
Energy efficiency Renewable energies Carbon capture and sequestration Biofuels
– Specific ‘wedges’ of mitigation– Externality: energy and water
Key reference
The ‘wedge’ paper: “A plan to keep carbon in check” by Socolow and Pacala, Scientific American, 2006.– This is an influential policy-oriented paper on how
to reform energy sector while still achieving economic growth
– Accessible through http://mirlyn.lib.umich.edu On local server: Socolow and Pacala
: Keeping Carbon in Check (Scientific American, 2006)
Future energy policy: What are we trying to achieve?
The 1992 UN Framework Convention on Climate Change was signed by most countries. Stated objective:“to achieve stabilization of GHG concentrations in the atmosphere at a low enough level to prevent dangerous anthropogenic interference with the climate system”
This should be done in a time frame sufficient:– to allow ecosystems to adapt naturally to climate change– to ensure that food production is not threatened– to enable economic development to proceed in a sustainable manner
Does ‘business as usual’ allow this? If not, then what energy policies should we introduce (as a world community)?
The green countries have signed UNFCCC!
Outline Lecture 2
Lecture 2: Future energy use and climate change mitigation
– ‘Business as usual’ Do we need to act to prevent ‘dangerous
anthropogenic interference’ in the climate system?
– ‘Wedges’ to mitigate climate change – Energy supply decarbonization ‘tools’
Energy efficiency Renewable energies Carbon sequestration Biofuels
– Specific ‘wedges’ of mitigation– Externality: energy and water
‘Business as usual’ CO2-trajectory path
‘Business as usual’ has CO2 emissions growing at current rate (1.5%/year)– Likely end-of-century warming: ~2.3 – 3.4 ºC
≈ business as usual
‘Business as usual’End-of-century temperature change
“Business as usual” (2090-2099) scenario– Global mean warming 2.8 ºC;– Much of land area warms by ~3.5 ºC– Arctic warms by ~7 ºC
Will ‘business as usual’ lead to ‘dangerous’ climate change?
At > 2ºC– Ecosystems become
threatened– Food supply
jeopardized– Abrupt / irreversible
changes (could lead to large-scale economic damage)
Many scientists think should prevent >2ºC warming EU policy aimed at < 2ºC warming
So what is a ‘safe’ CO2 trajectory and how do we achieve it?
Likely range of ‘business as usual’ by 2100
CO2 stabilization trajectory
Need to stay below ~2 ºC to avoid ‘dangerous’ climate change.
Stabilize at < 550 ppm. Pre-industrial: 275 ppm, current: 385 ppm.
Need 7 ‘wedges’ of prevented CO2 emissions.
Outline Lecture 2
Lecture 2: Future energy use and climate change mitigation– ‘Business as usual’
Why we need to act to prevent ‘dangerous anthropogenic interference’ in the climate system
–‘Wedges’ to mitigate climate change – Energy supply decarbonization ‘tools’
Energy efficiency Renewable energies Carbon sequestration Biofuels
– Specific ‘wedges’ of mitigation– Externality: energy and water
What is a ‘wedge’?
A ‘wedge’ is a strategy to reduce carbon emissions that grows from zero to 1 GtC/year in 50 years
The world needs to implement 7 of these wedges to prevent ‘dangerous’ climate change
Examples:– Expand wind energy– Make cars more efficient– Reduce deforestation rates
Developing Vs. developed world
Implementation of wedges would lead to large emission reductions in developed world
Developing world would increase emissions, but less than without carbon constraints
How and where to get the wedges
Need 7 wedges for 2xCO2 stabilization
Where and how is most cost-effective to cut CO2?
Tools wedges use:– Improved energy
efficiency– Renewable energies
(wind, solar)– Carbon capture and
sequestration– Biofuels
Outline Lecture 2
Lecture 2: Future energy use and climate change mitigation– ‘Business as usual’
Why we need to act to prevent ‘dangerous anthropogenic interference’ in the climate system
– ‘Wedges’ to mitigate climate change
– Energy supply decarbonization tools Energy efficiency Renewable energies Carbon capture and sequestration Biofuels
– Specific ‘wedges’ of mitigation– Externality: energy and water
Efficiency Gains
The low-hanging fruit! Essentially three kinds:
– End-use electricity efficiency (fluorescent bulbs instead of incandescent bulbs)
– Energy generation efficiency (coal plant operating at 60 % efficiency instead of current 40 %)
– Transportation efficiency (60 mpg instead of 30 mpg) Efficiency gains are generally cheap mitigation options But will only get so far before cutting into primary energy
used for economic activity
Kinds of renewable energy
Hydro-power– Already widely
used - not much potential for expansion
Wind– Abundant and
competitive
Solar – Photovoltaic (PV)– Concentrating solar
Renewable energy: Wind
Probably most promising renewable energy source
Supplies ~1 % of world electricity, ~0.3 % in US
Is cost-effective against coal and natural gas
Is undergoing very rapid growth (5-fold increase 2000-2007)
$0.00
$0.10
$0.20
$0.30
$0.40
1980 1984 1988 1991 1995 2000 2005
Wind energy cost in $/kWh
Renewable energy: Wind
Advantages:– Wind energy is relatively
mature technology and is cost effective
– Can be utilized at all scales Large wind farms On small agricultural farms
– Total theoretical potential of wind energy on land/near shore is 5x current energy consumptionLarge potential for expansion
Renewable energy: Wind
Disadvantages:– Horizon pollution and NIMBY
siting problems
– Birds…(though this is often over-stated – about 1-2 birds per turbine per year)
– Wind is intermittent! It can therefore not make up a large fraction of base load (unless effective energy storage)
Renewable energy: Solar Essentially three kinds:
1. Solar heat – Water is heated directly by
sunlight– Used cost-effectively on
small scale in houses
2. Solar photovoltaic (PV)– Uses photo-electric effect
(Einstein!) to produce electricity
– Supplies ~0.04 % of world energy use
3. Solar concentrated– Use large mirrors to focus
sunlight on steam turbine or very efficient PV panels
– More cost-effective than just PV
Renewable energy: Solar Advantages:
– Enormous theoretical potential!– Applicable at various scales
(individual houses to solar plants)– Solar heating can be cost effective– Economy of scale and/or
breakthroughs might reduce costs of PV and solar concentrated
Disadvantages– PV and solar concentrated are
expensive! Currently only cost-effective with government subsidies
– Intermittent – can not make up large portion of base load (except with storage capability)
Outline Lecture 2
Lecture 2: Future energy use and climate change mitigation– ‘Business as usual’
Why we need to act to prevent ‘dangerous anthropogenic interference’ in the climate system
– ‘Wedges’ to mitigate climate change – Energy supply decarbonization tools
Energy efficiency Renewable energies
Carbon capture and sequestrationBiofuels
– Specific ‘wedges’ of mitigation– Externality: energy and water
Carbon Capture and Sequestration (CCS)
Main idea:– Burn fossil fuels for
electricity/hydrogen production– Capture CO2
– ‘Sequester’ it in geological formation, oil/gas field, or ocean floor
This principle is immensely important for future CO2 mitigation!– Fossil fuels are abundant and cheap– Renewable energy generally not
mature enough to replace fossil fuels– Coal-fired power plants with CCS
could provide low-carbon energy at competitive costs
Currently successfully employed in ‘pilot’ projects
CCS: Carbon Capture Both conventional and modern types of
coal-fired power plants can be adapted for CCS
Conventional coal-fired power plant:– Burn coal in air (much like the old days)– Exhaust gas is ~15 % CO2 (rest is mostly
nitrogen and water vapor)– Exhaust gas flows over chemicals that
selectively absorb CO2 (‘amines’)– The amines are heated to ~150 ºC to give up
the CO2 and produce a (nearly) pure CO2 gas that can be sequestered.
Modern coal-fired power plant:– Coal is burned with pure oxygen in a
gasification chamber to produce hydrogen and CO2
– The CO2 is filtered out and the hydrogen is burned for electricity
CCS: Sequestration
1. Depleted oil/gas reservoirs (can be even be used to enhance oil/gas recovery – reduces costs)
2. Deep saline (brine) formations – these are porous media in which CO2 can be stored and dissolve in the salty water
3. Use for coal-bed methane recovery (one of those ‘unconventional’ fossil fuels)
4. Ocean floor (very controversial!)
CO2 can be sequestered at ~1 km underground, here pressure is high enough to liquify CO2, which helps prevent it from leaking
Several options for sequestering CO2:
Biofuels
Initially hailed as a sustainable substitute for oil
Can help reduce oil imports and improve national security – In US, this is probably main motivation
for recent push (“addicted to oil”, Bush’s 2006 State of the Union)
Two main kinds of biofuels:1. First generation:
Produced by converting sugar in corn, sugar beets, etc., into ethanol (alcohol)
2. Second generation:Produced through “cellulosic conversion” of biomass into sugar, then sugar into ethanol
Climate change impact of different biofuels is very different!
Biofuels – First Generation In US, mainly corn-based ethanol
– Heavily subsidized by federal government to reduce oil dependence (~$1.90/gallon)
Effect on climate change is negative:– Energy used in production is comparable to energy content– Significant amounts of N2O (a potent GHG) can be produced through fertilizer
use– More carbon would be sequestered by letting crop land lie fallow– Raises food prices Tropical deforestation, which releases more carbon
than saved from fuel production over > 30-year period
Source: Fargione et al., Science, 2008
Biofuels – Second Generation Produced from plants containing cellulose
– Cellulosic conversion to sugar is very difficult and expensive! (cows have 4 stomach compartments for a reason…)
Second generation biofuels are better for climate change:– Similar amount of carbon sequestered as fallow cropland– But, competition with food still leads to tropical deforestation and net
release of carbon!
US 1st generation
biofuel
US 2nd generation
biofuel
Biofuels – do they help or hurt? In general, biofuels that compete with food will not contribute to
mitigating climate change– Direct link between food demand/prices and tropical deforestation
Production of first generation biofuels (directly from food such as corn) is not a solution to climate change and should be avoided!
Production of second generation biofuels (from biomass) is only helpful if it doesn’t compete with food production (so not grown on cropland)– Second generation biofuels from agricultural waste could play important
role, but is currently not cost-effective
In light of these recent results (2007/2008), EU is reconsidering past biofuel mandates and subsidies
Outline Lecture 2
Lecture 2: Future energy use and climate change mitigation– ‘Business as usual’
Why we need to act to prevent ‘dangerous anthropogenic interference’ in the climate system
– ‘Wedges’ to mitigate climate change – Energy supply decarbonization ‘tools’
Energy efficiency Renewable energies Carbon sequestration Biofuels
–Specific ‘wedges’ of mitigation– Externality: energy and water
Where can we create ‘wedges’ in the energy system?
Power generation (40 %)– This is the ‘easy’ target because
of availability of cost effective low-carbon options (wind, CCS)
Direct fuel use (36 %) – This can be ‘switched’ to low-
carbon electricity
Transportation (24 %)– This is the tough nut to crack!– Currently no real feasible low
carbon alternatives Lot of infrastructure in place for
fossil fuel-based transportation!
??? ???
How to create ‘wedges’: Power Generation
Several options, each one wedge:– Increase efficiency of coal-fired
power plants from 40 to 60 % ($)– Replace coal-fired to natural gas-
fired power plants ($)– Double nuclear electricity to replace
coal-fired power plants ($$)– Use CCS for low-carbon coal-fired
power plants ($$)– Expand wind energy 30x to replace
coal-fired power plants ($$)– Expand solar energy 700x to
replace coal-fired power plants ($$$)
How to create ‘wedges’: Direct Fuel Use
Several options, each one wedge:– Improve building
insulation ($)– Replace natural gas
heat with low-carbon hydrogen from wind/coal with CCS ($$$)
– (and general switch to electricity heat instead of fuel heat)
How to create ‘wedges’: Transportation
Several options, each one wedge:– Increase car efficiency from 30
to 60 mpg ($)– More compact world with less
travel 5,000 instead of 10,000 miles/vehicle ($)
– Switch to low-carbon hydrogen ($$$)
– Switch to sustainable biofuels unlike corn ethanol, these must not compete with food production! ($$$)
Outline Lecture 2 Lecture 2: Future energy use and climate change
mitigation– ‘Business as usual’
Why we need to act to prevent ‘dangerous anthropogenic interference’ in the climate system
– ‘Wedges’ to mitigate climate change – Energy supply decarbonization ‘tools’
Energy efficiency Renewable energies Carbon sequestration Biofuels
– Specific ‘wedges’ of mitigation
–Externality: energy and water
Must address climate change without exacerbating freshwater shortage
Both energy and water are critical resources
Many areas already suffer water stress – note Africa, India, China, where
greatest population growth is projected to occur
Projected to become worse with increasing population, pollution, and climate change– Dry areas are generally projected
to become drier. Must address energy challenge
without exacerbating water scarcity
So where is our fresh water used?
You can take many, many, very long showers for a pound of steak…
Greatly expanding biofuels from ethanol to substitute oil would probably be bad idea…
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