Black Carbon - Emission Sources

Emission Sources

By Region: Developed countries were once the primary source of black carbon emissions, but this began to change in the 1950s with the adoption of pollution control technologies in those countries. Whereas the U.S. emits about 21% of the world’s CO₂, it emits 6.1% of the world’s soot. The European Union and United States might further reduce their black carbon emissions by accelerating implementation of black carbon regulations that currently take effect in 2015 or 2020 and by supporting the adoption of pending International Maritime Organization (IMO) regulations. Existing regulations also could be expanded to increase the use of clean diesel and clean coal technologies and to develop second-generation technologies.

Today, the majority of black carbon emissions are from developing countries and this trend is expected to increase. The largest sources of black carbon are Asia, Latin America, and Africa. China and India together account for 25-35% of global black carbon emissions Black carbon emissions from China doubled from 2000 to 2006. Existing and well-tested technologies used by developed countries, such as clean diesel and clean coal, could be transferred to developing countries to reduce their emissions

Black carbon emissions “peak close to major source regions and give rise to regional hotspots of black carbon—induced atmospheric solar heating.” Such hotspots include “the Indo-Gangetic plains in South Asia; eastern China; most of Southeast Asia including Indonesia; regions of Africa between sub-Sahara and South Africa; Mexico and Central America; and most of Brazil and Peru in South America.”. Approximately three billion people live in these hotspots.

By Source: Approximately 20% of black carbon is emitted from burning biofuels, 40% from fossil fuels, and 40% from open biomass burning, according to Ramanathan. Similarly, Dr. Tami Bond of the University of Illinois, Urbana Champaign, estimates the sources of black carbon emissions as follows:

• 42% Open biomass burning (forest and savanna burning)

• 18% Residential biofuel burned with traditional technologies

• 14% Diesel engines for transportation

• 10% Diesel engines for industrial use

• 10% Industrial processes and power generation, usually from smaller boilers

• 6% Residential coal burned with traditional technologies

Black carbon sources vary by region. For example, the majority of soot emissions in South Asia are due to biofuel cooking, whereas in East Asia, coal combustion for residential and industrial uses plays a larger role. In Western Europe, traffic seems to be the most important source since high concentrations coincide with proximity to major roads or participation to (motorized) traffic.

Fossil fuel and biofuel soot have significantly greater amounts of black carbon than climate-cooling aerosols and particulate matter, making reductions of these sources particularly powerful mitigation strategies. For example, emissions from the diesel engines and marine vessels contain higher levels of black carbon compared to other sources. Regulating black carbon emissions from diesel engines and marine vessels therefore presents a significant opportunity to reduce black carbon’s global warming impact.

Biomass burning emits greater amounts of climate-cooling aerosols and particulate matter than black carbon, resulting in short-term cooling. However, over the long-term, biomass burning may cause a net warming when CO₂ emissions and deforestation are considered. Reducing biomass emissions would therefore reduce global warming in the long-term and provide co-benefits of reduced air pollution, CO₂ emissions, and deforestation. Johannes Lehmann of Cornell University estimates that by switching to slash-and-char from slash-and-burn agriculture, which turns biomass into ash using open fires that release black carbon and GHGs, 12% of anthropogenic carbon emissions caused by land use change could be reduced annually, which is approximately 0.66 Gt CO₂-eq. per year, or 2% of all annual global CO₂-eq emissions.