For the millions of people who descend on Munich for the annual bash, Oktoberfest is a celebration of beer, bands and bratwurst.

But as the dust settles for another year on the world’s largest folk festival, and die Bierleichen (“beer corpses”) return to the land of the living, environmental scientists have released the first analysis of methane emissions from the 16-day party.

Researchers at Technical University in Munich walked and cycled around the perimeter of the festival last year with mobile sensors aloft. The instruments found the event emitted nearly 1,500kg of methane – 10 times the amount that wafted off Boston, Massachusetts, in the same period.

The scientists attributed most of Oktoberfest’s emissions to leaks and incomplete combustion in cooking and heating appliances. Though an appreciable part of the rise in the gas, about 10%, was attributed to the flatulence and burps of attendees.

Jia Chen, who studies greenhouse gases in urban environments, said: “The observed methane concentrations cannot solely be explained by biogenic sources.

“We have strong indications that fossil fuel methane emissions by gas grills and heating appliances are major sources.”

After carbon dioxide, methane is the second most common greenhouse gas emitted by human activity. Though shorter-lived, it is more effective than carbon dioxide at heating the atmosphere and accounts for about 20% of global heating due to anthropogenic greenhouse gas emissions since 1750. Atmospheric levels of the gas have surged in recent years for reasons scientists cannot fully explain.

Having noticed a spike in Munich’s methane levels during Oktoberfest in previous years, Chen and her colleagues decided to monitor the event to see whether major festivals made important contributions to greenhouse gas emissions.

More than six million people visit Oktoberfest each year and make their way through more than seven million litres of beer, 100,000 litres of wine, half a million chickens and a quarter of a million sausages.

To Chen’s surprise, on average, every square metre of Oktoberfest in 2018 released 6.7 micrograms of methane per second. Less than 10% was calculated to come from festivalgoers in the form of flatulence and burps, according to a paper submitted to the journal Atmospheric Chemistry and Physics.

Chen believes the work can help festival organisers draw up policies to reduce their methane emissions. The study concludes the releases of methane are high enough for major festivals to be considered greenhouse gas sources in local emissions inventories.

“Large but time-limited festivals, like Oktoberfest, are sources that have not been accounted for in existing emission inventories, even though, as we have seen, the methane emissions are significant,” Chen said. “Inaccurate or incomplete emission inventories are a problem, because many decisions

are based on this data.”

With people travelling to Oktoberfest from more than 50 countries, methane leaks from the Theresienwiese site are not the greatest environmental concern. But improving gas appliances to reduce methane emissions still makes sense, Chen said. “Small steps can bring us closer to achieving the world climate goals,” she added.

