The temperatures in the biomeiler pile are measured with thermocouples buried in several locations. Nine of them are found at three heights (1’, 2’, and 3’ above the ground) in the inner core, outer core, and mantle of the pile. The graph in today’s post shows the temperatures measured by thermocouples at 3’ height. These sensors are buried 1’ below the upper surface of the pile. A sheet of Reflectix, a tarp, and some snow lie above the top of the pile.
In previous posts, I described how the biomeiler was, contrary to expectation, cooling the air passing through the vent pipe into the coop. The cooling effect was due to cold water from melting ice dripping down through the pile. The cooling effect began to diminish in June and, by the second week of July, this remarkable phenomenon had come to an end.
At the time the cooling effect ended, the data from the thermocouples revealed the start of another process. In the graph we see that the temperature profile in the pile reverses during the second week of July. The pile began the month hotter on the outside and cooling toward the center. However, by the 13th, the inner core of the pile was the hottest region and the outer layers were progressively cooler.
This switch in the temperature gradient indicates that composting has resumed in the center and the pile is once again behaving in the traditional manner, generating heat. Because of the absence of aeration in the pile since the start of summer, I conclude that the composting must be due to the action of anaerobic bacteria.
The resumption of heating was not confined to the uppermost portions of the pile. At all depths, the temperatures steadily rose during the month. At the 2’ height, the temperature profile reversed in the third week. At the 1’ height, the profile reversed in the last week of the month.
As mentioned in yesterday’s post, the readings were discontinued on the 28th because we left for a vacation. During the fall, I will analyze the results with the goal of redesigning the biomeiler for the coming winter heating season. Any work of that sort will probably begin in September.
