O2Compost Hot Topics
Successful Manure & Waste Management
The Curing Phase
September 9th, 2008 by peter
QUESTION: Three weeks into the aeration process, our temperatures have dropped from 130 degrees to 80 degrees. The airflow has been increased but it doesn’t seem to make a difference. Is this normal?
ANSWER: It sounds like everything is going as planned. In general, heat results from the biologic activity during the first 21-30 days but the actual duration of heat generation is a function of the available carbon and the amount of nitrogen in the feedstocks. With horse manure composting, the readily available carbon - simple sugars, proteins, etc. - are utilized quickly leaving the more resilient forms of carbon (cellulose and lignin) to be degraded over time. As as result, the pile temperature tends to jump up quickly and then fall off in 3 to 4 weeks. This is referred to as the “active phase”.
Following the active phase, the compost pile transitions into what we call “curing’. While active composting is a bacterial-driven process, curing is a fungal-driven process and takes place at cooler temperatures. You should see mushrooms growing on top and a white fibrous material growing in the top 12-18 inches. This is called actinomycetes and it is a very good thing given that it is working on the cellulose in the manure balls and lignin in the bedding. To produce a truly stable product, curing can take 30-60 days following active composting.
The one thing to watch for is the moisture content of your mix. Pile temperatures will plummet if the moisture content drops much below 45%. The mix should fee wet to the touch and when you squeeze a handful, you should be able to get a drip or two or a bead of water between your fingers. To determine this, take a posthole digger and dig a vertical hole and see what the materials look like, to to bottom.
Also, when we meet the oxygen demand of the micro-organisms during the active phase, additional airflow will actually cool the pile down because we are displacing the hot air with cooler air. To increase the pile temperature, try reducing the airflow and see if the pile temperatures rebound at all. If your mix is wet and you don’t see a rebound, then you are likely in the curing phase.
Leave a Reply
You must be logged in to post a comment.