Cleaning Up Diesel Exhaust Improves Both Health & Climate

Diesel engine exhaust has long been known to promote cardiovascular disease and lung cancer. A new understanding of one of the components of diesel exhaust shows it is also a powerful driver of climate change, with black carbon particles 3,200 times more damaging to the climate than carbon dioxide in the near-term. By controlling the dangerous components in diesel exhaust, as many OECD countries have done, we get co-benefits: reduced harm to both health and climate.

“Addressing these emissions is a possible win-win. It’s not only about health but potential climate benefits as well,” said World Bank Senior Environment Specialist Sameer Akbar, who led a new report examining the co-benefits of reducing diesel emissions for development and climate action.

In the near term, reducing the amount of black carbon emitted into the environment can slow the rate of global temperature increase.

A number of OECD countries have already cut these emissions dramatically. However, in low- and middle-income countries, where the majority of all black carbon is emitted, emissions are expected to grow as economies develop. Transportation accounts for nearly 20 percent of global black carbon emissions and most of it is estimated to come from older diesel engines without emission control equipment and using high sulfur diesel fuel in low- and middle-income countries. These countries have the opportunity to learn from the experience of OECD countries in reducing emissions, and achieve significant benefits for both climate and health. 

To help decision makers estimate the benefits of diesel emission controls, the World Bank has published a new study, Reducing Black Carbon Emissions from Diesel Vehicles: Impacts, Control Strategies, and Cost-Benefit Analysis.

The study, conducted by the International Council for Clean Transportation, summarizes a series of technical and policy options already demonstrated to cut the health and climate risks from diesel emissions. It also introduces a new analytical framework to monetize the benefits of black carbon emissions reduction.

Diesel Exhaust

In countries without adequate controls, diesel engines spew a toxic mix of small particles known as particulate matter. These fine particles, which can be inhaled deeply into the lungs, have long been known to harm health. The International Agency for Cancer Research, a UN agency, has labeled them as carcinogenic. The American Heart Association has warned that these particles can result in premature deaths and disability from cardiovascular events, including heart attacks and stroke. The particles are also believed to trigger or exacerbate chronic bronchitis and childhood asthma.

The health case against particulate matter is so solid that several industrialized countries have taken steps to nearly eliminate it. Controlling dangerous diesel exhaust can be accomplished in a number of ways including changing to cleaner fuels, requiring the use of specialized exhaust filters, encouraging better engine design and even buying older vehicles, to send to scrap heaps, or to replace them with cleaner vehicles.

Lately, climate researchers have focused on one of the components in fine particulate matter, the particles of black carbon. A 2013 assessment concluded that after CO2, black carbon is the second most important pollutant in the atmosphere in terms of its global warming impacts in the near-term, and that diesel exhaust is one of the predominant sources that are very rich in black carbon emissions. 

A New Framework

All diesel emission controls produce benefits, but they also have costs. To aid countries in choosing ways to control diesel emissions, the World Bank study introduces a new analytical framework.

The framework broadens existing analytical approaches by estimating values for the social benefits of black carbon mitigation for climate impacts as well as for health impacts. Determining the social costs of black carbon is a piece of work in its early days, building on the on-going work  on the social cost of carbon, which is increasingly being used in OECD countries to monetize the impacts of CO2 emissions.  

In the World Bank’s study, the framework was applied to four different project simulations: diesel engine retrofits in Istanbul, Turkey; green freight in Sao Paulo, Brazil; fuel and vehicle standards in Jakarta, Indonesia; and compressed natural gas buses in Cebu, Philippines. In all four cases, health benefits dominated the cost-benefit calculus and, in two simulations, the benefits of the control measures were enhanced by the climate benefits.

The framework is an early effort toward a more comprehensive assessment of the ways sustainable development can contribute to multiple benefits, including toward climate mitigation. For example, the framework could be broadened by adding other components, such as loss of agriculture production and damage to ecosystems. It is a significant advance because it allows for assessing the health and climate benefits of diesel black carbon emissions reduction initiatives.  

“We are now beginning to have the tools, the metrics, and the information to start expanding the economic analysis to factor climate benefits of black carbon mitigation into the cost-benefit equation,” Akbar said.