Cars and not Cows are causing rising ammonia emissions, say researchers

Researchers at the Oak Crest Institute of Science in California used a technique called remote sensing in order to examine the individual emissions of 4500 vehicles, and found unexpectedly high levels of ammonia in the exhaust of petrol-powered cars.

Until now, scientists believed that decomposition of livestock waste was the main source of atmospheric ammonia, according to Marc Baum, principal investigator on the study.

Some theorise that reformulated gasoline, introduced in the mid-1990’s to lower sulphur emissions, has contributed to the increased ammonia emissions and, according to a recent study in the journal Environmental Science and Technology, catalytic converters may also play a role in the increase.

The evidence collected by the Oak Crest researchers also suggests that there are certain types of car which are producing the bulk of the ammonia. Though 70% had detectable levels of ammonia emissions, just 10% generated 66% of ammonia.

Aside from cars and dairy farms, major sources of ammonia emissions include fertilisers and sewage treatment plants, say the Oak Crest researchers.

Also reported this week in the Los Angeles Times, is a campaign by neighbourhood groups and environmentalists to block new dairy farm projects. The objection is to millions of pounds of manure dumped in slurry lagoons which can be as large as several football fields, and which, campaigners claim, pose a serious threat to air and water quality.

The campaign comes despite the fact that air quality has improved significantly during the last decade, according to data from the California Air Resources Board, the LA Times reports.