Importance of Aeration to Optimize Compost Process and Reduce Area

Composting of animal manures is usually done with turned windrows. We had the opportunity to try out a self propelled windrow turner, so we too made turned windrows with dairy cattle manure (70% moisture which is usual for solid dairy manure).  We observed that the temperature inside the windrow did not reach 55 C, and the oxygen concentration remained almost zero, already 2 hours after turning. More importantly, when we withdrew air from the center of the pile, it was odorous. Composting theory would have told us that the material was too wet, and we would have to add additional dry material. This was not a great option for us, as this increases the amount of material to compost and increases the area required for composting. This location receives up to 1.5 m of rain between October and March which means that the material has to be covered.

Instead, we placed a 4″ aeration pipe between the two windrows and rolled the two windrows into one larger windrow using the loader. Within an hour of aeration with a 1/2″ hp blower and timer, the oxygen concentrations remained above 5%. The temperature increased to > 55 C, and there was no longer odor in the air that was withdrawn from the center of the pile.

We were achieving a faster composting process in less than 1/2 the area that was required for the two turned windrows. Two or three mixes of the material is still required for a consistent quality product, but we achieved a large space and operational cost saving.

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