Millions of people convene at large festivals like Carnival in Rio de Janeiro and Dia de los Muertos in Mexico City. These gatherings are more than just wild parties or cultural heritage, however—they’re a rich trove of scientific data. Researchers now have calculated the methane emissions associated with Oktoberfest, a harvest celebration held in the fall in Munich, Germany. The scientists found that Oktoberfest’s area-normalized methane flux was about half that of an average dairy farm. Festivals—often unaccounted for in emissions inventories—can be significant, albeit temporary, sources of greenhouse gases, the team concluded.
Beer, Sausage, and Methane
At Munich’s Oktoberfest, typically held over 16 days, revelers consume more than 8,000,000 liters of beer and copious amounts of grilled sausages, fish, and oxen. But the natural gas used to heat Oktoberfest’s massive tents and power its grills consists primarily of methane, which is a potent greenhouse gas: Kilogram for kilogram, methane traps roughly 30 times as much energy as carbon dioxide.
Jia Chen, an electrical engineer focused on environmental science at the Technical University of Munich, and her colleagues set out to quantify Oktoberfest’s methane emissions. “Festivals could be a notable methane source even though they have not yet been included in the existing emission inventories,” said Chen. “Oktoberfest is the largest folk festival worldwide.”
Many Rounds for Science
In 2018, Chen and her collaborators walked and biked around the 2.5-kilometer perimeter of the Oktoberfest site carrying portable methane sensors. The team made 94 rounds with the instruments, which were about the size of a backpack and weighed roughly 11 kilograms. “It’s good exercise,” said Chen.
The sensors determined gas concentrations by pumping air into a cavity and then measuring the attenuation of different wavelengths of laser light. The team combined these data with wind information to accurately estimate methane fluxes. “The higher the wind speed, the lower concentration we will measure because the methane is more diluted,” said Chen.
The researchers found that on average, about 7 micrograms of methane per second were being emitted from each square meter of the Oktoberfest premises. That’s significant and only about a factor of 2 smaller than the flux escaping from a dairy farm, the team noted. (Cows are notorious methane emitters, mostly because of their belches.)
Roughly 20% of these emissions can be ascribed to biogenic methane produced by attendees’ exhalations and flatulence, Chen and her colleagues calculated on the basis of published estimates. The remainder, the researchers suggest, likely derived from incomplete combustion in gas-powered heaters or cooking appliances. Chen and her collaborators also found that methane fluxes were higher on weekends when more visitors were in attendance. That’s not surprising, because these emissions are all anthropogenic in nature, the team concluded.
These results were published last month in Atmospheric Chemistry and Physics.
Allowed in the Next Time
In 2019, the researchers returned to Oktoberfest, this time on the actual premises. “We were allowed to go inside,” said Florian Dietrich, an engineer at the Technical University of Munich and a member of the team. “We went closer to the sources.”
This time, they made measurements with portable methane sensors and also collected air samples. Back in the laboratory, they determined the ratio of ethane to methane in the samples to shed light on the origin of the emissions—biogenic sources produce very little ethane, whereas fossil fuels (e.g., natural gas) typically contain ethane. The results are being prepared for publication.
“There are so many different sources of methane,” said Ben Poulter, a carbon cycle scientist at the NASA Goddard Space Flight Center in Greenbelt, Md., not involved in the research. “Studies like this help individuals understand their greenhouse gas footprint a little bit better.”
—Katherine Kornei (@KatherineKornei), Science Writer