Kerosene Lamps Pack Big Climate Punch

Kerosene lamps glow nightly in communities across the developing world. New research shows that these tiny lights have a greater impact than expected on climate (Environ. Sci. Technol., DOI: 10.1021/es302697h). Inefficient lamps burning kerosene release about 270 gigagrams of black carbon particulate matter into the atmosphere every year, the researchers estimate. This level of emissions is similar to that of the shipping industry.

When kerosene or other hydrocarbons combust inefficiently, they produce tiny soot particles called black carbon that absorb heat from sunlight because of their dark color. Black carbon absorbs heat to a greater extent than greenhouse gases can, despite the fact the particles don’t last as long in the atmosphere as the gases do. One ton of black carbon in the atmosphere can warm the climate as much as 700 tons of carbon dioxide over a century, according to previous estimates.

While climate scientists know approximately how much black carbon is in the atmosphere, they can’t fully account for all of its sources. Nicholas Lam of the University of California, Berkeley, Tami Bond of the University of Illinois, Urbana-Champaign, and their colleagues thought kerosene lamps in the developing world could be one of the missing sources. They formed this hypothesis after speaking with people about the large amount of soot produced from kerosene lamps in their homes. To test the idea, the team decided to determine exactly how much black carbon these lamps released.

Teaming with scientists in India and Uganda, Bond and Lam’s team measured black carbon produced when burning different kerosene fuels. They tested simple wick lamps typically found in Uganda and elsewhere that consist of a wick or rope dipped in fuel. Using electrochemical and nondispersive infrared sensors, the scientists burned the lamps and monitored real-time levels of black carbon in people’s homes. To confirm their measurements, team members studied similar lamps in their lab in Illinois. They measured black carbon levels using the same methods, along with collecting particulate matter from the lamps on filters in flow chambers.

The team found that on average, 1 kg of kerosene fuel burned in these lamps produced 90 g of black carbon. Based on the team’s estimates of the amount of kerosene used in home lamps in the developing world, the researchers calculated that the lamps produce about 3% of the black carbon found in the atmosphere.

As a comparison, boats that ship freight around the world produce 2% of total black carbon emissions, says Daniel Lack of the National Oceanic and Atmospheric Administration, who was not involved in the study. At the same time, the lamps use significantly less fuel than the boats, highlighting the inefficiency of the lamps, he says. Providing more-efficient lighting to people in the developing would help cut black carbon emissions, Lack says. Bond adds that people can more readily control black carbon emissions from kerosene lamps, unlike other major sources of black carbon such as forest fires.