Working Group III: Mitigation

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5.4 Sector- and Technology-specific Barriers and Opportunities

GHG emissions from some sectors are larger than those from others, and the importance of each GHG varies across sectors as well. Methane (CH4) for instance is a much bigger contributor to emissions from agricultural activity than, for instance, from the industry sector. Table 5.4 shows the carbon emissions from energy use in 1995. Emissions from electricity generation are allocated to the respective consuming sector. Carbon emissions from the industrial sector clearly constitute the largest share, while those from agricultural energy use form the smallest share. In terms of growth rates of carbon emissions, however, the fastest growing sectors are transport and buildings. With rapid urbanization promoting increased use of fossil fuels for habitation and mobility in many countries, the two sectors are likely to continue to grow faster than others will in the future.

Annual carbon emissions from land-use change were estimated in the IPCC Special Report on Land Use, Land-use Change and Forestry at 1.6 ±0.8GtC/yr for the period 1989 to 1998 (IPCC, 2000a). Tropical forests are estimated to be net emitters, but temperate and boreal forests are net sequesters of carbon. CH4 emissions from livestock, rice paddies, biomass burning, and natural wetlands add up to 1.8GtCeq/yr with considerable uncertainty about these estimates. Below we describe the sector-specific barriers to and opportunities for reducing the sectoral GHG emissions.

Table 5.4: Carbon emissions from fossil fuel combustion (MtC)
Sector Carbon emissions and % share1
Average annual growth rate (%)
1971 to 1990 1990 to 1995
Industry Buildings 2370 (43%) 1.7 0.4
--Residential 1172 (21%) 1.8 1.0
--Commercial 584 (10%) 2.2 1.0
Transport 1227 (22%) 2.6 2.4
Agriculture 223 (4%) 3.8 0.8
All sectors 5577 (100%) 2.0 1.0
--Electricity generation2 1762 (32%) 2.3 1.7
1 Emissions from energy use only; does not include feedstocks or carbon dioxide from calcination in cement production. Biomass = no emissions.
2 Includes emissions only from fuels used for electricity generation. Other energy production and transformation activities are not included.
Source: Price et al., 1999

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