Pig farmers report black foam rising from under floors

North American pig farmers have reported several occurrences in the past year of large volumes of black foam rising from under slatted floors which can produce hazardous gases.

As the gases are released and become trapped by foam at the surface, the foam builds up.

When the foam is disturbed by pig activity, power washing, water sprinklers or agitation, it releases methane and hydrogen sulphide gas.

Methane concentrations inside the foam are 60%-70%, which is above explosive concentration.

When foam bubbles are broken, methane accumulates under pig shed ceilings, and becomes explosive.

When methane exceeds about 5% of the air volume, and there is a flame or spark from a heater pilot light, electric or gas motor, or light switch, an explosion may occur.

This has been the case on about six pig farms in the midwestern US since 2009.

The black foam started appearing in the last four or five years there and experts don’t know where it has come from.

Possible causes are new bacteria or a chemical change in pig waste.

There is some speculation that it is the latter and that the ultimate cause is distillers, dried grains, and solubles (DDGS).

DDGS is a byproduct of the ethanol industry and is being used at increasingly higher levels in pig diets.