There is a small but rising number of reports of cattle slurry bubbling and foaming up through cattle slats, usually after agitation. In a handful of instances the resulting gas has been ignited by sparks from a welder or angle grinder, causing a large but brief flash of flame.

Roscommon drystock farmer Peter Naughton agitated this tank on Saturday 12 April. The following morning, froth had bubbled up through the slat ribs. But by evening the foam was spilling across the feed passage.

“I sucked out one tank on the Sunday evening but it came right back up. I took out another two on Monday, one each on Tuesday and Wednesday and that got it down 2ft below the slats.”

The picture shows the tank a few days ago. The slurry continues to bubble and foam up, despite further tanker fills being removed. The foaming is being caused by vigorous activity by methane-producing bacteria. Methane is, of course, explosive. Peter has no idea why this has happened in this tank, just one of four in his yard.

“The tanks are here years. I did nothing different last winter, there was no contamination of the tank, I didn’t import any silage or anything.”

He is wondering if it will recur next spring and spread to the other tanks.

With a neighbour, Peter removed a bucketful of slurry from the tank and put a flame to it.

“The gases burned. It is methane. When you disturb the bubbles in the foam you get the smell. Farmers who experience foaming of slurry tanks should be careful not to ignite it.”