Climate Change 2001:
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3.3 Sectoral Mitigation Technological Options7

Figure TS.5: Carbon in oil, gas and coal reserves and resources compared with historic fossil fuel carbon emissions 1860-1998, and with cumulative carbon emissions from a range of SRES scenarios and TAR stabilization scenarios up until 2100. Data for reserves and resources are shown in the left hand columns. Unconventional oil and gas includes tar sands, shale oil, other heavy oil, coal bed methane, deep geopressured gas, gas in acquifers, etc. Gas hydrates (clathrates) that amount to an estimated 12,000 GtC are not shown. The scenario columns show both SRES reference scenarios as well as scenarios which lead to stabilization of CO2 concentrations at a range of levels. Note that if by 2100 cumulative emissions associated with SRES scenarios are equal to or smaller than those for stabilization scenarios, this does not imply that these scenarios equally lead to stabilization.

The potential8 for major GHG emission reductions is estimated for each sector for a range of costs (Table TS.1). In the industrial sector, costs for carbon emission abatement are estimated to range from negative (i.e., no regrets, where reductions can be made at a profit), to around US$300/tC9. In the buildings sector, aggressive implementation of energy-efficient technologies and measures can lead to a reduction in CO2 emissions from residential buildings in 2010 by 325MtC/yr in developed and EIT countries at costs ranging from -US$250 to -US$150/tC and by 125MtC in developing countries at costs of -US$250 to US$50/tC. Similarly, CO2 emissions from commercial buildings in 2010 can be reduced by 185MtC in developed and EIT countries at costs ranging from -US$400 to -US$250/tC avoided and by 80MtC in developing countries at costs ranging from -US$400 to US$0/tC. In the transport sector costs range from -US$200/tC to US$300/tC, and in the agricultural sector from -US$100/tC to US$300/tC. Materials management, including recycling and landfill gas recovery, can also produce savings at negative to modest costs under US$100/tC. In the energy supply sector a number of fuel switching and technological substitutions are possible at costs from -US$100 to more than US$200/tC. The realization of this potential will be determined by the market conditions as influenced by human and societal preferences and government interventions.

Table TS.2 provides an overview and links with barriers and mitigation impacts. Sectoral mitigation options are discussed in more detail below.

3.3.1 The Main Mitigation Options in the Buildings Sector

The buildings sector contributed 31% of global energy-related CO2 emissions in 1995, and these emissions have grown at an annual rate of 1.8% since 1971. Building technology has continued on an evolutionary trajectory with incremental gains during the past five years in the energy efficiency of windows, lighting, appliances, insulation, space heating, refrigeration, and air conditioning. There has also been continued development of building controls, passive solar design, integrated building design, and the application of photovoltaic systems in buildings. Fluorocarbon emissions from refrigeration and air conditioning applications have declined as chlorofluorocarbons (CFCs) have been phased out, primarily thanks to improved containment and recovery of the fluorocarbon refrigerant and, to a lesser extent, owing to the use of hydrocarbons and other non-fluorocarbon refrigerants. Fluorocarbon use and emission from insulating foams have declined as CFCs have been phased out, and are projected to decline further as HCFCs are phased out. R&D effort has led to increased efficiency of refrigerators and cooling and heating systems. In spite of the continued improvement in technology and the adoption of improved technology in many countries, energy use in buildings has grown more rapidly than total energy demand from 1971 through 1995, with commercial building energy registering the greatest annual percentage growth (3.0% compared to 2.2% in residential buildings). This is largely a result of the increased amenity that consumers demand - in terms of increased use of appliances, larger dwellings, and the modernization and expansion of the commercial sector - as economies grow. There presently exist significant cost-effective technological opportunities to slow this trend. The overall technical potential for reducing energy-related CO2 emissions in the buildings sector using existing technologies combined with future technical advances is 715MtC/yr in 2010 for a base case with carbon emissions of 2,600MtC/yr (27%), 950MtC/yr in 2020 for a base case with carbon emissions of 3,000MtC/yr (31%), and 2,025MtC/yr in 2050 for a base case with carbon emissions of 3,900MtC/yr (52%). Expanded R&D can assure continued technology improvement in this sector.

Table TS. 1: Estimations of greenhouse gas emission reductions and cost per tonne of carbon equivalent avoided following the anticipated socio- economic potential uptake by 2010 and 2020 of selected energy efficiency and supply technologies, either globally or by region and with varying degrees of uncertainty
US$/ tC avoided
References, comments, and relevant section in Chapter 3 of this report
Residential sector OECD/ EIT Acosta Moreno et al., 1996;
Brown et al., 1998
Dev. cos.31 Wang and Smith, 1999
Commercial sector OECD/ EIT  
Dev. cos.  
Automobile efficiency improvements USA Interlab. Working Group, 1997
Brown et al., 1998
Europe US DOE/ EIA, 1998
ECMT, 1997 (8 countries only)
Japan Kashiwagi et al., 1999
Denis and Koopman, 1998
  Dev. cos. Worrell et al., 1997b
CO2 removal - fertilizer; refineries Global Table 3.21
Material efficiency improvement Global Table 3.21
Blended cements Global Table 3.21
N2O reduction by chem. indus. Global Table 3.21
PFC reduction by Al industry Global Table 3.21
HFC-23 reduction by chem. industry Global Table 3.21
Energy efficient improvements Global Table 3.19
Increased uptake of conservation tillage and cropland management Dev. cos. Zhou, 1998; Table 3.27
Dick et al ., 1998
Global IPCC, 2000
Soil carbon sequestration Global Lal and Bruce, 1999
Table 3.27
Nitrogenous fertilizer management OECD Kroeze & Mosier, 1999
Table 3.27
Global OECD, 1999; IPCC, 2000
Enteric methane reduction OECD Kroeze & Mosier, 1999
Table 3.27
USA OECD, 1998
Reimer & Freund, 1999
Dev. cos. Chipato, 1999
Rice paddy irrigation and fertilizers Global Riemer & Freund, 1999
IPCC, 2000
Landfill methane capture OECD Landfill methane USEPA, 1999
Energy supply              
Nuclear for coal Global   Totalsc - See Section 3.8.6
Annex I Table 3.35a
Non- Annex I Table 3.35b
Nuclear for gas Annex I Table 3.35c
Non- Annex I Table 3.35d
Gas for coal Annex I Table 3.35a
Non- Annex I Tables 3.35b
CO2 capture from coal Global Tables 3.35a + b
CO2 capture from gas Global Tables 3.35c + d
Biomass for coal Global Tables 3.35a + b
Moore, 1998; Interlab w. gp. 1997
Biomass for gas Global Tables 3.35c + d
Wind for coal or gas Global Tables 3.35a - d
BTM Cons 1999; Greenpeace, 1999
Co-fire coal with 10% biomass USA Sulilatu, 1998
Solar for coal Annex I Table 3.35a
Non- Annex I Table 3.35b
Hydro for coal Global Tables 3.35a + b
Hydro for gas Global Tables 3.35c + d

a Potential in terms of tonnes of carbon equivalent avoided for the cost range of US$/ tC given.
= <20 MtC/ yr      = 20- 50 MtC/ yr      = 50- 100MtC/ yr      = 100- 200MtC/ yr      = >200 MtC/ yr

b Probability of realizing this level of potential based on the costs as indicated from the literature.
= Very unlikely      = Unlikely      = Possible      = Probable      = Highly probable

c Energy supply total mitigation options assumes that not all the potential will be realized for various reasons including competition between the individual technologies as listed below the totals.

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