Effect of Sulfur Levels in Diesel Fuel and LAC

On June 2012, the UNEP Partnership for Clean Fuels and Vehicles (PCFV), which supports developing countries in their efforts to improve fuel and vehicle technologies that reduce air pollution, announced the latest updated data on the global status of sulfur levels in diesel.

According to these data, limits on sulfur content are typically less than 50 parts per million (ppm) in developed countries, and often less than 15 ppm. However, the sulfur level in diesel fuel in many developing countries, including in Latin America and the Caribbean (LAC), is still very high. Chile, Costa Rica, Puerto Rico and Virgin Islands are the only countries in the Latin America and Caribbean region which currently utilize low sulfur diesel fuel (sulfur levels below 50 ppm).  Other countries across the region are in the process of transitioning towards low sulfur fuels, but this is happening too slowly whilst other countries have no regulatory plans in the pipeline.

Sulfur in diesel fuel forms sulfur dioxide (SO2) and sulfate (SO4) particulate matter (PM) during combustion. These pollutants raise particulate levels including ambient fine PM levels. SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract. Furthermore, when SO2 combines with water, it forms sulfuric acid; this is the main component of acid rain.

In addition to these air quality and environmental impacts, sulfur in diesel fuel contributes to increased acid levels in the engine and causes serious damage on engine and emission control systems. The presence of sulfur in the engine exhaust limits the effectiveness of many exhaust after treatment technologies, resulting in higher emissions of other pollutants such as volatile organic compounds, particles, CO and NOx.  Therefore, using low sulfur diesel fuel directly reduces ambient SO2 and fine PM levels, improves engine and after treatment system durability, and enables new technologies to be commercially viable. The introduction of ultra low sulfur diesel and subsequently low pollutant emission vehicle technologies should therefore be prioritized as an easily achievable action and accelerated in developing countries.

The Clean Air Institute is seeking to tackle this and other related issues through its Sustainable Transport and Air Quality (STAQ) program funded by the Global Environment Facility and the World Bank.  One of the Program’s regional objectives is to expand the Clean Air Initiative for Latin America and Caribbean.  This is a network of local and national governments, stakeholders, international organizations and private sector entities with a common goal of protecting the health of people exposed to air pollution, while achieving GHG emission reductions and other co-benefits in LAC cities and across the Region.  From this platform CAI intends to facilitate the faster take up of low sulfur fuels through knowledge sharing, build institutional and technical capacity and increasing the profile of such issues in the region.