Climate Change 2001: Mitigation

Other reports in this collection

3.3.2 The Main Mitigation Options in the Transport Sector

In 1995, the transport sector contributed 22% of global energy-related carbon dioxide emissions; globally, emissions from this sector are growing at a rapid rate of approximately 2.5% annually. Since 1990, principal growth has been in the developing countries (7.3% per year in the Asia-Pacific region) and is actually declining at a rate of 5.0% per year for the EITs. Hybrid gasoline-electric vehicles have been introduced on a commercial basis with fuel economies 50%-100% better than those of comparably sized four-passenger vehicles. Biofuels produced from wood, energy crops, and waste may also play an increasingly important role in the transportation sector as enzymatic hydrolysis of cellulosic material to ethanol becomes more cost effective. Meanwhile, biodiesel, supported by tax exemptions, is gaining market share in Europe. Incremental improvements in engine design have, however, largely been used to enhance performance rather than to improve fuel economy, which has not increased since the SAR. Fuel cell powered vehicles are developing rapidly, and are scheduled to be introduced to the market in 2003. Significant improvements in the fuel economy of aircraft appear to be both technically and economically possible for the next generation fleet. Nevertheless, most evaluations of the technological efficiency improvements (Table TS.3) show that because of growth in demand for transportation, efficiency improvement alone is not enough to avoid GHG emission growth. Also, there is evidence that, other things being equal, efforts to improve fuel efficiency have only partial effects in emission reduction because of resulting increases in driving distances caused by lower specific operational costs.

3.3.3 The Main Mitigation Options in the Industry Sector

Industrial emissions account for 43% of carbon released in 1995. Industrial sector carbon emissions grew at a rate of 1.5% per year between 1971 and 1995, slowing to 0.4% per year since 1990. Industries continue to find more energy efficient processes and reductions of process-related GHGs. This is the only sector that has shown an annual decrease in carbon emissions in OECD economies (-0.8%/yr between 1990 and 1995). The CO2 from EITs declined most strongly (-6.4% per year between 1990 and 1995 when total industrial production dropped).

Differences in the energy efficiency of industrial processes between different developed countries, and between developed and developing countries remain large, which means that there are substantial differences in relative emission reduction potentials between countries.

Improvement of the energy efficiency of industrial processes is the most significant option for lowering GHG emissions. This potential is made up of hundreds of sector-specific technologies. The worldwide potential for energy efficiency improvement - compared to a baseline development - for the year 2010 is estimated to be 300-500MtC and for the year 2020 700-900MtC. In the latter case continued technological development is necessary to realize the potential. The majority of energy efficiency improvement options can be realized at net negative costs.

Another important option is material efficiency improvement (including recycling, more efficient product design, and material substitution); this may represent a potential of 600MtC in the year 2020. Additional opportunities for CO2 emissions reduction exist through fuel switching, CO2 removal and storage, and the application of blended cements.

A number of specific processes not only emit CO2, but also non-CO2 GHGs. The adipic acid manufacturers have strongly reduced their N2O emissions, and the aluminium industry has made major gains in reducing the release of PFCs (CF4, C2F6). Further reduction of non-CO2 GHGs from manufacturing industry to low levels is often possible at relatively low costs per tonne of C-equivalent (tCeq) mitigated.

Sufficient technological options are known today to reduce GHG emissions from industry in absolute terms in most developed countries by 2010, and to limit growth of emissions in this sector in developing countries significantly.

Table TS.3: Projected energy intensities for transportation from 5-Laboratory Study in the USAa
Energy efficiency
New passenger car l/100km
New light truck l/100km
Light-duty fleet l/100kmb
Aircraft efficiency (seat-l/100km)
Freight truck fleet l/100km
Rail efficiency (tonne-km/MJ)
a BAU, Business as usual; HE/LC, high-energy/low-carbon.
b Includes existing passenger cars and light trucks.

3.3.4 The Main Mitigation Options in the Agricultural Sector

Agriculture contributes only about 4% of global carbon emissions from energy use, but over 20% of anthropogenic GHG emissions (in terms of MtCeq/yr) mainly from CH4 and N2O as well as carbon from land clearing. There have been modest gains in energy efficiency for the agricultural sector since the SAR, and biotechnology developments related to plant and animal production could result in additional gains, provided concerns about adverse environmental effects can be adequately addressed. A shift from meat towards plant production for human food purposes, where feasible, could increase energy efficiency and decrease GHG emissions (especially N2O and CH4 from the agricultural sector). Significant abatement of GHG emissions can be achieved by 2010 through changes in agricultural practices, such as:

  • soil carbon uptake enhanced by conservation tillage and reduction of land use intensity;
  • CH4 reduction by rice paddy irrigation management, improved fertilizer use, and lower enteric CH4 emissions from ruminant animals;
  • avoiding anthropogenic agricultural N2O emissions (which for agriculture exceeds carbon emission from fossil fuel use) through the use of slow release fertilizers, organic manure, nitrification inhibitors, and potentially genetically-engineered leguminous plants. N2O emissions are greatest in China and the USA, mainly from fertilizer use on rice paddy soils and other agricultural soils. More significant contributions can be made by 2020 when more options to control N2O emissions from fertilized soils are expected to become available.

Uncertainties on the intensity of use of these technologies by farmers are high, since they may have additional costs involved in their uptake. Economic and other barriers may have to be removed through targetted policies.

Other reports in this collection

IPCC Homepage