Ethanol emissions

A technique has been developed that allows scientists to track urban atmospheric plumes from manmade biofuels using a unique isotopic signature found in vehicle emissions.

Ethanol is used in making biofuels and as these fuels become more widely used, interest in their influence on air quality is increasing. When biofuels are burnt the remaining ethanol emitted as exhaust has a much higher 13C to 12C ratio than the ethanol naturally emitted by tropical plants. A study published in Environmental Science & Technology has suggested that this signature can be used to track plumes as they drift away from urban areas.¹

The researchers collected and analysed air from downtown Miami, Florida, USA, and the nearby Everglades National Park. The components of the air samples from the two locations were first separated using gas chromatography, before the abundance of each carbon isotope was measured via a mass spectrometer. The study found that 75% of ethanol in Miami’s urban air came from manmade biofuels, while the majority of ethanol in the Everglades air was emitted from plants, even though a small quantity of city pollution from a nearby road floats into the park.

It is estimated that plants currently release three times as much ethanol as manmade sources but the authors of the study warn that as the amount of ethanol used in fuels increases this should change.

1. B.M. Giebel, P.K. Swart and D.D. Riemer, Environ. Sci. Technol., 45(15), 6661–6669 (2011).

This story originally appeared in The Column. Click here to view that issue.