Sources and Sinks of Greenhouse Gases

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Sources and Sinks of Greenhouse Gases

• Lecture 3

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Introduction

• The greenhouse gases
• Sources
• Emissions
• Reducing emissions of CO2
• Carbon management

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Greenhouse gases
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Estimated anthropogenic contributions to global
warming

• Source IPCC 1997

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The carbon reservoirs

• Atmosphere CO2
• Land living biota and organic matter
• Ocean dissolved CO2, small creatures

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The carbon cycle

• .

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Carbon dioxide (CO2)

• Atmospheric CO2
• 1890 280ppm
• 2000 360ppm
• 2050 600ppm

Time trend in atmospheric CO2 concentration at
Mauna Loa Observatory, Hawaii (Keeling et al.,
1995).
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Carbon dioxide (CO2)

• Rising by 1.5 ppm per year
• Average atmospheric lifetime 50 - 200 years
• Growth rate 0.45
• Anthropogenic sources
• Fossil fuel combustion (75)
• Deforestation (24)
• Cement production (1)

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CO2 emissions influenced by

• Size of human population
• Amount of energy used per person
• Level of emissions resulting from that use of
  energy

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CO2 emissions can be reduced by

• Improving energy efficiency
• Fuel switching
• Use of renewable energy
• Nuclear power
• Capture and storage of CO2

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Methane (CH4)

• Atmospheric concentration
• 1860 750 ppb
• 2000 1750 ppb
• Average atmospheric lifetime
• 12 years
• Growth rate 0.6

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Methane (CH4)

• Natural sources
• anaerobic decomposition of organic substances in
  biological systems
• wood digestion by termites
• oceans, seas and lakes

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Methane (CH4)

• Anthropogenic sources
• Fossil fuel extraction (20)
• Dams, reservoirs (20)
• Livestock digestion (18)
• Rice paddies (17)
• Landfill sites (10)
• Animal manure/slurry (7)

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UK methane emissions
Source National Atmospheric Emissions Inventory
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Nitrous oxide (N2O)

• Atmospheric concentration
• 1860 285ppb
• 2000 312 ppb
• Average atmospheric lifetime 120 years
• Growth rate 0.25

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Nitrous oxide (N2O)

• Natural sources
• Oceans
• Soils
• Forests
• Meadows

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Nitrous oxide (N2O)

• Anthropogenic sources
• Poor soil management (70)
• Transport (14)
• Industrial processes (7)

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UK N2O emissions
Source National Atmospheric Emissions Inventory
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Halogenated compounds

• Contain
• Fluorine
• Chlorine
• Bromine
• Iodine

• All are greenhouse gases
• Halogens with carbon and chlorine or bromine
  cause ozone depletion
• CFCs
• Halons
• HCFCs

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Chlorofluorocarbons (CFCs)

• Example CFC 12
• Atmospheric concentration
• 1860 0
• 2000 533 ppt
• Average atmospheric lifetime 102 years
• Growth rate 1

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Chlorofluorocarbons (CFCs)

• Anthropogenic sources
• aerosol propellants
• blowing agents for plastic foams
• refrigerants
• solvents

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CFC replacements

• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• Sulphur hexafluoride (SF6)

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HFCs, PFCs and SF6

• Industrial processes
• Levels increasing
• Very long lifetime

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Reducing CO2 emissions

• UK government aim
• UK to a low carbon economy
• EU emissions trading scheme
• Start 2005
• Mandatory for some companies
• Penalties if goals not met

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Carbon management

• The Carbon Trust
• 5 steps

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Step 1. Evaluate business case

• Develop an overall understanding of climate
  change and its risks and opportunities for your
  company

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Step 2. Develop strategic objectives

• Develop and agree overall objectives and approach
  to carbon management

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Step 3. Identify opportunities

• Establish a detailed picture of company-wide
  emission assets and liabilities
• Generate and evaluate specific ideas for
  achieving cost effective emission reductions

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Step 4. Develop an implementation plan

• Prioritise ideas, reflecting overall corporate
  objectives and aspirations
• Develop an overall implementation plan including
  specific emission reduction targets

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Step 5. Manage implementation

• Monitor the progress of the plan and its
  effectiveness in delivering the specified
  objectives
• Review progress and update plan accordingly

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How to reduce emissions

• Buy green energy
• http//www.greenelectricity.org/
• Best supplier of green energy
• http//www.greenprices.com/uk/pricesbox.asp

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Driving tips to reduce energy

• Avoid hard acceleration
• Keep your speed down
• Only make essential car journeys
• Walk or cycle on short trips
• Share car journeys with others
• Service the car regularly
• Check your tyre pressure every week
• Travel outside the rush hour to avoid congestion
• Travel light and remove unnecessary loads and
  roof racks

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Save energy to reduce emissions

• Electricity use
• Fuel use

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British Sugar

• 40 reduction in energy
• 40 reduction in water usage

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References

• www.vegansociety.com/html/whyvegan/whyenvt.html
• www.futureforests.com/explainmore/reduceyouremissi
  ons.asp
• www.earthfuture.com/stormyweather/greenhouse/
• www.met-office.gov.uk/research/hadleycentre/models
  /carbon_
• cycle/intro_global.html
• http//www.aeat.com/netcen/airqual/naei/annreport/
  annrep98/na ei98.html
• http//www.climate.org.ua/ghg/ghg_.html
• http//www.britishsugar.co.uk
• Petit et al., 1999
• Keeling et al., 1995
• IPPC-Working Group 1, 2001