black carbon and global warming - impacts of common fuels ed. 2009-2009-00100-01-00

7/27/2019 Black Carbon and Global Warming - Impacts of Common Fuels Ed. 2009-2009-00100-01-00

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Black Carbon and

Global Warming:Impacts of Common Fuels

A Scientiic Review

Atlantic Consulting


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Black Carbon and Global Warming: Impacts of Common Fuels 3

Contents

1 Why this report? 4

2 What is Black Carbon? 4

3 Black Carbon and Global Warming 6

3.1 BC contributes signicantly to Global Warming 6

3.2 Although mechanisms dier to conventional GHGs, cutting BC does curb warming 7

4 Fuel Footprints: What i Black Carbon were included? 8

5 Conclusion: More attention and action needed 9

6 Reerences 10


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4 Black Carbon and Global Warming: Impacts of Common Fuels

1 Why this report?As a result o high-prole policy discussions, media coverage, and public debate, global warming (GW) is becomingan increasingly prominent issue. Perhaps driven by a need to explain this complex phenomenon in simple, accessibleterms, many commentators have adopted the habit o presenting carbon dioxide (CO

2) (oten simply called carbon)

as the unique cause o the problem and - by extension - the sole key to the solution. While there is no doubt that CO2

emissions are the largest contributor to global warming, the near-exclusive ocus on them poses the danger o masking

additional elements that need to be addressed.

This report examines the nature and role in global warming o another signicant emission; Black Carbon (BC). Despitethe act that BC emissions remain unregulated under the Kyoto Protocol and other prominent regulations aimed atcombating climate change, ndings suggest that it is probably the second largest contributor to global warming. Moreover,as has already been consistently documented by experts rom the World Health Organisation and national authorities,BC compromises both outdoor and indoor air quality. BC and other Particulate Matter (PM) can cause serious healthproblems and have been to shown to substantially reduce average liespans.A

This report is one attempt towards raising recognition o BC among policy-makers. Ater an overview o what BlackCarbon is, the report reviews the currently understood role o BC in global warming, and it demonstrates the carbonootprints o three common uels in two common applications: automobile transport and residential heating, taking BCemissions into account.

Available research suggests that adapting uture regulation and policy with a view to limiting BC emissions couldsigniicantly slow global warming. It would also yield beneits in terms o human health, reducing the social burdenassociated with illness and reduced lie expectancy as well as the associated costs. However, policies or reducing BCare not necessarily the same as those or reducing CO

2. Indeed, such policies can confict with each other in some cases.

For optimum reductions in global warming emissions, policy-makers need to consider the trade-os between CO2

andBC, and other global warmers such as methane. The undamental objective is not to reduce CO

2emissions but to slow

or reverse the process o global warming and its harmul impacts on humanity and the natural environment.

2 What is Black Carbon?Picture a replace, a burnt eld or orest, or the dark residue in a boilers ring chamber this is how many laypeopleencounter BC. Commonly reerred to as soot, this residue is actually a mixture o BC B, another type o carbon called

Organic Carbon (OC) and inorganic ash and salts.

BC is emitted primarily as a result o combustion (burning); more specically rom incomplete and/or inecient com-bustion. Due to a lack o oxygen or a low temperature, some o the carbon in the uel converts to BC rather than toCO

2. BC is almost always emitted together with other substances, in particles o varying s izes. There are many types o

particles in the air, emitted by a variety o sources, containing varying amounts o BC.

Specic emissions o BC are not usually monitored directly, but are instead estimated rom PM and BC actors. Nearlyall global BC emiss ions come rom combustion, the bulk o which is man-made. According to research led by Universityo Illinois Bond (2004), the sources o BC emissions vary considerably by region (Figure 1), with residential emissionsdominating in developing countries and transport/industry emissions dominating in the developed world.

A According to the World Health Organization (WHO): air pollution with PM claims an average o 8.6 months rom the lie o every person in the EU. http://www.euro.who.int/mediacentre/PR/2005/20050414_1

B Oten also reerred to as elemental carbon (EC).

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Carbon neutrality of wood fuel?

Most carbon ootprints assume carbon neutrality o wood or other biomass used as uel, i.e. biogenic CO2

isassigned a GWP o zero. In recent years, however, this method has come into question. First came the issue oland-use change, which is no longer accepted as automatically carbon neutral. Signicant losses o carbon stockdue to land-use change (or instance, deorestation to create cropland) should now be included in most ootprints.

More recently, researchers such as Rabl (2007), Johnson (2009) and Searchinger et al (2009) have proposedthat carbon-stock changes in general should be tracked in biouels accounting. As Searchinger et al (2009) put it:Under any crediting system, credits must refect net changes in carbon stocks, emissions o non-CO

2greenhouse

gases, and leakage emissions resulting rom changes in land-use activities to replace crops o timber divertedto bioenergy.

BC emissions themselves are not usually monitored. Instead, they are generally estimated as a product o two actors: PM10 or PM2.5 emissions rom a given uel and/or a given application BC content o that PM emission

PM emission actors are published or a wide range o uels and application. PM2.5 actors are published less requentlythan PM10s because measurement o the ormer began later. Studies conducted in the past ve years tend to inc ludePM2.5; studies beore that less so.

Figure 1: Overview of global BC emissions, by region and by sector

Black carbon

PowerIndustryTransport RoadTransport Non-roadResidential: Other

Residential: CoalResidential: BiouelFraction contained% o globa l contained

North America

Central/S Amer

Europe

Former USSR

Middle East

Pacic

Arica

China

India

Other Asia

Total

0% 25% 50% 75% 100%

Note : Sectoral contributions to emissions o black and organic carbon emissions.The grey bars behind the coloured bars represent the raction o emissions romcontained combustion (that undertaken or energy use, excluding open burning)in each region. The green bars to the let indicate the relative contr ibution o eachregion to the total.

Source: Bond et al.:A technology-based g lobal inventor y of black and organ ic car bonemissions from combustion. Journal o Geophysic al Research, Vol. 109


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3 Black Carbon and Global WarmingThrough a var iety o physical mechanisms, BC contributes to global warming. Over the past 10-15 years, the signicanceo its contribution has been increasingly recognised. Indeed its impact is now identied as being second only to that oCO

2, the worlds primary warming emission.

Putting BC on a like-or-like ooting with CO2

and other conventional global warmers is complicated, because BC acts

more locally than CO2, has an atmospheric residence time o weeks - as opposed to years - and can be co-emitted

with compounds that also cause cooling. Nonetheless, climate scientists agree that cutting BC emissions could substan-tially slow warming. This implies the need or a re-think o exist ing c limate policy. When emission reduction eor ts arerevised to include BC, rather than being limited exclusively to conventional global warmers, new trade-os and policyconsiderations come into play. For instance, biomass combustion broadly encouraged under exi sting policy appearsmuch less attractive once BC emissions are taken into account. Decarbonization takes on a double meaning, reerringnot to just CO

2but also to BC.

3.1 BC CONTRIBUTES SIGNIFICANTLY TO GLOBAL WARMING

According to estimates by Stanord Universitys Jacobson (2007), BC accounts or 16% o global warming, leaving itsecond only to CO

2. Estimates by the UNs Intergovernmental Panel on Climate Change (IPCC) in its Fourth Assess-

ment Report (2007) appear to corroborate this assumption.

BCs temperature eects occur through several mechanisms , which can vary according to region. Primarily, BC absorbssunlight and radiates it back to the atmosphere as heat. It also aects cloud ormation and rainall patterns. When BCsettles back to the ear ths surace, it can increase the melting rate o ice and snow, which makes it par ticularly signicantin colder regions. For instance, experiments by Ramanathan (2009) o the Center or Clouds, Chemistry and Climateat the Scripps Institution o Oceanography suggest that BC and CO

2play nearly equal roles in inducing springtime

snow-cover loss in Eurasia. Similar work by NASAs Drew Shindell nds that hal or more o the warming measuredin the Arctic rom 1976-2007 is due to soot, i.e. BC plus OC (Kintisch, 2009) most notably as a result o its eect onsnow albedo.C

C

Albedo is the term used to describe the extent to which an object or substance, snow in this case, diusely refects light rom light sources such as the sun.

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3.2 ALTHOUGH MECHANISMS DIFFER TO CONVENTIONAL GHGs,CUTTING BC DOES CURB WARMING

BC acts more locally than CO2because it is airborne or a shor ter period o time. Also, it aects local climate due to its

infuence on cloud ormation and r ainall. An additional dierence is that BCs atmospheric res idence time is measuredin weeks, not years, meaning that the convention o using 100-year horizons or global warming analyses understatesBCs impact in the short term, say in a 20-year horizon (Figure 2). For BC, data on 20 year GWP may thereore be the

most relevant. In any case, ndings suggest that the BCs relative warming potential is considerable.

Table 1: Relative Global Warming Potential of a selection of key emisssions

Emission

Global Warming PotentialD Relative to CO2

20 Year Period 100 Year Period

CO2

1 1

Methane 72 25

Nitrous Oxide (NOx) 289 298

Black Carbon 2200 680

Ramanathan (2009) and others emphasise the potential or a reduction in BC emissions to cut warming in the short-term, i.e. 15-20 years. Jacobson (2007) has shown that over the coming two decades reducing emissions o BC wouldbring about temperature reductions more rapidly than equivalent reductions o methane or CO

2emissions.

D Data or CO2, methane and nitrous oxide are rom 2007 IPCC Fourth Assessment Report (AR4) by Working Group 1 (WG1) and Chapter 2 o that repor t

(Changes in Atmospheric Constituents and in Radiative Forcing) which contains GWP inormation. Data or BC are rom Hill (2009).

Global warming potential

Global warming potential (GWP) quanties

the globa l warming (rad iative orcing) gener-ated by a given mass o any substance over agiven time. Given mass is typically specied inkilogrammes or tonnes, given time as 20, 100and 500 years. The GWP o carbon dioxide,the primary g lobal warming substance, is de-ned as 1, so GWPs o all other substancesare dened relatively to CO

2, i.e. as CO

2

equivalents (CO2e). GWPs can vary widely,

depending primar ly on: how much inrared ra-diation the substance absorbs; and how longthe substance per sists in the atmosphere .

Carbon ootprints are the product o:

substance mass (usually kilogrammes or tonnes) x GWPso they are typically expressed in kg or t CO

2e over 20, 100 or 500 years.

Although GWP as a measurement is generally accepted, some researchers contend that other measures, suchas Carbon dioxide Equivalency Factors (CEFs) or Global Temperature Potentials (GTPs), may in some cases bemore suitable or guiding policy.

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4 Fuel Footprints: What i Black Carbon

were included?Most carbon ootprints account only or so-called homogeneous greenhouse gases (GHGs) that are specied by theIPCC as global warmers: CO

2, CH

4, N

2O, and halocarbons. Footprints generally do not include gases or par ticles which

are not regulated by the IPCC such as black carbon or other heterogeneous species such as carbon monoxide (CO),hydrogen (H

2), organic carbon (OC), ozone (O

3), nitrogen oxides (NOx) or sulphates (SOx).

The inclusion o t hese additional global warmer s allows or a more complete assessment o the global warming oot-prints o dierent uels in speciic applications, oten modiying relative warming impacts.

For example (Figures 4 and 5), Liquied Petroleum Gas (LPG) can be compared to diesel in an automotiveapplication and to wood as a heating uel:

Figure 2: Carbon footprints of LPG and diesel as automotive fuels

Figure 3: Carbon footprints of LPG and wood as heating fuels

Diesel LPG

Non-IPCC listed GlobalWarmers (notably B lackCarbon)

Conventional GlobalWarmers (notably carbondioxide)

Wood, i assumedto be carbon

neutral

LPG Wood, notassumed to becarbon neutral

Non-IPCC listed GlobalWarmers (notably BlackCarbon)

Conventional GlobalWarmers (notably carbondioxide)

Relative Global Warming Impact (GWP 20) per Gigajoule in CO2

equivalent

Relative Global Warming Impact (GWP 20) per km in CO2

equivalent

Global warming its not just about CO2

Because carbon dioxide is the primary anthropogenic global warmer, global warmer emissions are otenreerred to generically as carbon. And some climate change regulations or instance the European UnionsEmissions Trading System cover only emissions o carbon dioxide.

However, other anthropogenic emissions contribute signiicantly to global warming, including: methane,nitrous oxide, a wide variety o halocarbons, black carbon, carbon monoxide and nitrogen oxides.


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5 Conclusion: More attention and action neededWhile ur ther research is needed in order to corroborate and to clar iy existing data, it is increasingly clear that BlackCarbon is a major contributor to global warming. The primarily anthropogenic origin o these emissions suggests thatthere may be scope or reducing them v ia policy measures designed to encourage citizens to (a) use energy more e-ciently and (b) use energy resources whose combustion leads to relatively lower levels o BC emissions. One possibletransition, applicable in both developed and develop ing regions, would be to reduce emissions associated with biomass

and diesel. In the developing world, a shit rom traditional tomodern cooking stoves could deliver a two-or-one eect: lessglobal warming and better human health.

The IPCC already recognises BC as a signicant global warmer.The UNs Economic Commission or Europe nds that urgentaction to decrease (Black Carbon) concentrations in the at-mosphere would provide opportunities, not only or signicantair pollution benets (e.g. health and crop-yield benets), butalso or rapid climate benets, by helping to slow global warm-ing and avoid crossing critical temperature and environmentalthresholds.E In the US, two ederal bills have been proposed,one in the House o Representatives and one in the Senate.The House billF would authorise research to develop BC regula-tion and would require the US Environmental Protection Agencyto propose specic regulations within a year o being enacted.

Preliminary evidence suggests that this may constitute a uniqueopportunity or Europe and indeed the world to achieve signi-cant warming reductions within a 20 year window. This, combinedwith the more widely understood human health benets associatedwith a reduction o PM concentrations in the ambient air, shouldcombine to make BC emissions a subject o increasing impor-tance and urgency in the coming years.

E From UNECEs Executive Body or the Convention on long-range transboundary air pollution, meeting in Geneva, 15-18 December 2008. Item 13 o provisionalagenda. Air pollution and climate change: developing a ramework or integrated co-benets strategies.

F

H.R. 1760, B lack Carbon Emissions Reduction Act o 2009, http://www.govtrack.us/congress/bill.xpd?bill=h111-1760&tab=summary

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6 ReerencesBond T.C. Black carbon and climate change . In: Representatives U.H.o., ed. Washington DC, 2007.Brakkee K.W., Huijbregts M.A.J., Eickhout B., Hendriks A.J., Meent D.v.d. Characterisation Factors or GreenhouseGases at a Midpoint Level Including Indirect Eects Based on Calculations with the IMAGE Model. International Journalof LCA2008;13:191-201.California Air Resources Board. Multiple Air Toxics Exposure Study (MATES-II). 2000.

Delucchi M. CO2

Equivalency Factors, Appendix D. A Liecycle Emissions Model (LEM): Liecycle Emissions FromTranspor tation Fuels, Motor Vehicles, Transpor tation Modes, Electricity Use, Heating and Cooking Fuels, and Mater ials:University o Cal iornia, Davis, 2003.EcoInvent. EcoInvent LCI Database. St Gallen, Switzerland.EMF-22. Black Carbon Update. EMF-22 Meeting. Tsukaba, Japan, 2006.Friedrich R. Natural and biogenic emissions o environmentally relevant atmospheric trace constituents in Europe.

Atmospher ic Environment2009;43:1377-1379.Fuglestvedt J.S., Shine K.P., Berntsen T., Cook J., Lee D.S., Stenke A., Skeie R.B., Velders G.J.M., Waitz I.A. Transportimpacts on atmosphere and climate: Metrics.Atmospher ic Environment2009;2009:1-30.Gaegauf C.K., Schmid M.R., Gntert P. Elemental and Organic Carbon in Flue Gas Particles o Various Wood Combus-tion Systems. 8th International Conerence on Energy or a Clean Environment, Lisbon 2005 Contact: www.oekozen-trum.ch. Lisbon, 2005.Hill L.B. The Carbon Dioxide-Equivalent Benets o Reducing Black Carbon Emissions rom U.S. Class 8 Trucks UsingDiesel Particulate Filters: A Preliminary Analysis. 2009.Jacobson M.Z. Black carbon and global warming. In: Representatives U.H.o., ed. Washington DC, 2007.Johnson, E. Goodbye to carbon neutral: getting biomass ootprints right. Environmental Impact Assessment Review

2009;29(3):1658.Joint Research Centre of the EU Commission, EUCAR, CONCAWE. Well-to-Wheels analysis o uture automotiveuels and powertrains in the European context. 2006.Kintisch E. New push ocuses on quick ways to curb global warming. Science 2009;324:323.Knzli N., Kaiser R. , Medina S., Studnicka M., Chanel O., Filliger P., Herry M., Jr F.H., Puybonnieux-Texier V., Qunel P.,

Schneider J., Seethaler R., Vergnaud J.-C., Sommer H. Public-health impact o outdoor and trac-related air pollution:a European assessment. The Lancet2000;356:795-801.Rabl, A., Benoist A. et al. How to account or CO2 emissions rom biomass in an LCA. International Journal of LCA2007;12(5):281 DOI:http://dx.doi.org/10.1065/lca2007.06.347.Ramanathan V. Black carbon orcing and its climate eects. International Workshop on Black Carbon. London, 2009.Reddy M.S., Boucher O. Climate impact o black carbon emitted rom energy consumption in the worlds regions.

Geophysical Research Letters 2007;34:L11802.Riffel B. Estimating the Carbon Dioxide Equivalency Factor (CEF) Associated with Emissions o Nitrogen Oxides(NOx). Caliornia, Davis, 2007: 101.Searchinger, T.D., Hamburg, S.P., et al. Fixing a critical climate accounting error. Science Vol. 326, October 23, 2009,DOIA:10,1126/Science.1178797Smith K.R., Uma R., Kishore V.V.N., Zhang J., Joshi V., Khalil M.A.K. Greenhouse Implications o household stoves: AnAnalysis or India.Annual Review of Energy and the Env ironment2000;25:741-763.Stedman J .R., King K., Holland M., Walton H. Quantication o the health eects o air pollution in the UK or revisedPM10 objective analysis. 2002.US EPA. Particulate Matter Emissions. Indicator, 2008.US EPA. PM Composition & Sources. 2006.US EPA. PM proles, Titles and documentation. 2005.Wichmann H.-E. Positive gesundheitliche Auswirkungen des Einsatzes von Par tikelltern bei Dieselahrzeugen Risiko-abschtzung r die Mortalitt in Deutschland. Umweltmed Forsch Prax 2004;9:58-99.


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black carbon and global warming - impacts of common fuels ed. 2009-2009-00100-01-00

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