Global black carbon emissions from transportation by region among top 10 motorized regions, 2000-2050. Source: Minjares et al., data from Facanha et al. (2012). Click to enlarge.

Black carbon has been found to be second to carbon dioxide in terms of its climate forcing. (Earlier post.) Black carbon is 3,200 times more effective on a mass-equivalent basis than carbon dioxide in causing climate impacts within 20 years, and 900 times more effective within 100 years.

Black carbon increases global and regional temperatures when emitted into the atmosphere, where individual particles directly absorb energy from the sun and radiate it back as heat. Black carbon also reduces the strong cooling effect of large, highly reflective surfaces such as glaciers and Arctic ice. High concentrations of black carbon in the atmosphere can change precipitation patterns and reduce the amount of radiation that reaches the Earth’s surface, which affects local agriculture.

In addition to the climate effects, exposure to particulate matter is associated with a range of diseases, including chronic bronchitis and asthma, as well as premature deaths from cardiopulmonary disease, lung cancer, and acute lower respiratory infections.

In 2012 the International Agency for Research on Cancer re-categorized diesel engine exhaust as carcinogenic to humans based on evidence that sufficient exposure is associated with an increased risk of lung cancer. (Earlier post.)

Controlling diesel black carbon emissions in developed countries has successfully relied on fuel quality improvements and vehicle emissions standards. Such standards require new vehicles to be equipped with filters and to use ultra-low-sulfur diesel (ULSD). This enables the use of diesel particulate filters and the adoption of strict emissions standards (e.g., Euro 6/VI). However, the report notes, refinery investment in upgrades or importation are key to the availability of ULSD in developing countries.

Furthermore, the report notes, no developing country has adopted fuel and vehicle standards equivalent to Euro 6/VI. Among non-OECD countries, Brazil has adopted the most stringent fuel and vehicle standards, followed closely by Russia. Brazil may adopt more stringent fuel quality standards by 2015; similarly tough vehicle standards are less certain, according to the authors.

China and India have made significant progress in moving to Euro 4/IV standards for light- and heavy-duty vehicles; some major cities, including Delhi and Beijing, have taken steps to advance beyond the national requirements.

Implementation of improved fuel and vehicle standards, which requires both government regulation and enforcement, may be difficult however in regions where governance is weak and technical capacity is limited. Emissions control strategies should be both sensitive to local needs and aim for maximum feasible reductions guided by best practices. Policy roadmaps can be a useful tool in providing greater predictability of interventions.

—“Reducing Black Carbon Emissions from Diesel Vehicles”

Other programs can provide significant benefits, such as vehicle scrappage and replacement, inspection and maintenance, and vehicle retrofitting, the report suggested. Complementary policies to limit growth in travel demand and long-term growth in emissions include fuel taxation, congestion charging, and logistics management, among other strategies.

Cost benefit. This study applied a new cost-benefit analysis methodology to four simulated diesel black carbon emissions control projects—diesel retrofit in Istanbul; green freight (plus retrofit) in São Paulo; fuel and vehicle standards in Jakarta; and Compressed Natural Gas (CNG) buses in Cebu—taking into account the additional climate benefits of black carbon reductions.

The study found that for some projects, the net benefits were positive only when assuming a large benefit from black carbon control on the climate in the near term (using 20 years Global Warming Potential or GWP) and a low social cost-of-carbon discount rate.

The analysis demonstrates that consideration of black carbon may make some projects viable that otherwise would not be considered worthwhile. While investments in many diesel emissions control projects can be justified without the consideration of black carbon, the inclusion of black carbon into a cost-benefit modeling framework was found to provide a more comprehensive assessment. In two of the four cases the health benefits of diesel emissions control alone were substantial enough to justify the interventions; the other two projects became viable only with the inclusion of climate benefits.

Further work is needed to fully test this methodological framework with real-world projects and to establish clearer guidelines for the incorporation of black carbon into cost-benefit analysis. Additional work is also needed to narrow the range of assumptions for the discount rate tied to the social cost of carbon as well as the Global Warming Potential. Importantly, a social cost of black carbon needs to be developed and alternative methodologies need to be explored whereby temperature response and damage functions (for climate impacts) are applied.

—“Reducing Black Carbon Emissions from Diesel Vehicles”

Resources

• Minjares, Ray et al. (2014)“Reducing Black Carbon Emissions from Diesel Vehicles: Impacts, Control Strategies, and Cost-Benefit Analysis” (Nº 86485)