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				2010		2020		References, comments, and relevant section in Chapter 3 of this report
	Region	-400	-200	0	+200	Potentiala	Probabilityb	Potentiala	Probabilityb
Buildings/appliances
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.
Transport
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
Manufacturing
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
Agriculture
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
Wastes
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
Notes: 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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