German police said the explosion in the central German town of Rasdorf last week was caused by methane from 90 flatulent cows. But researchers told DairyReporter.com it is more likely it was a build-up of methane in a badly ventilated manure pit.
“We think it is definitely not methane from the cows themselves,” said Dr Jan Dijkstra, associate professor in ruminant nutrition, Wageningen University.
Trapped methane
The amount of methane a cow produces is estimated at 500L a day. Air becomes volatile when it contains 6% to 16% (60,000-160,000ppm) methane. In Dutch dairy cow sheds, the average amount of methane does not normally exceed 50 ppm (0.08% of the lowest explosive limit), researchers say.
Another source of methane is the break-down of manure organic matter in the slurry storage.
Although methane production from the manure pit is normally lower than the amount produced by animals, the levels can increase when old unwanted or spilled feed gets into the pit. Manure pits may start foaming, trapping methane gas in air bubbles.
The explosion happened last Monday when a static electrical charge ‘caused the gas to explode with flashes of flames.’ A roof was damaged and one cow was treated for burns.
Pig stye incidents
Dijkstra said it is the first incident of a methane explosion in a cow shed he is aware of.
“The manure pit is the most likely explanation, because you see this happen now and then in pig styes. Pigs hardly produce any methane, but their manure does.”
“The more organic matter in manure, the higher levels of methane,” he said. “Farmers should try to avoid putting old feed in the manure, as that is lots of organic matter. There should be precautions, for example when emptying the pit. And farmers should have well ventilated manure pits.”
Wageningen UR is a collaboration between Wageningen University and the DLO Foundation (Service Agricultural Sciences). Based in the Netherlands with a presence around the world, Wageningen UR’s three areas of research are food and food production; living environment; and health lifestyle and livelihood.