Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Biosystems Engineering Technology

Major Professor

C. Roland Mote

Committee Members

Bobby L. Bledsoe, Dan L. McLemore


A series of thirteen (13) static compost piles were constructed during the period of June, 1985 to March, 1986 at the University of Tennessee Dairy Experiment Station near Lewisburg, Tennessee. The study was performed to investigate the relationship among various compost process parameters (e.g., method of aeration, pile size, and time) and the moisture content and coliform bacteria population in composted dairy waste intended for use as bedding in free stalls.

Both natural and forced aeration methods were employed to supply oxygen to the piles of manure solids. The natural aeration method consisted of nothing more than aging the manure solids in an unconfined pile. The forced aeration method employed a fan to force air into a perforated plenum located underneath the compost pile. The forced aeration system was controlled by either a cycle time switch or a temperature set point controller sensing pile temperature.

Temperatures of the compost mass were monitored daily at three (3) levels within each pile. Samples from three (3) levels were analyzed for moisture content and total coliform bacteria populations on a weekly basis. A heterotrophic plate count - spread plate method was used to enumerate the total coliform bacteria.

Results of the temperature study suggest that the fan had an impact on the composting process such that the piles with the fan reached a higher internal temperature than the piles without the fan. Further, the time to reach maximum temperature was lower for the piles with the fan than for the piles without the fan. However, piles without the fan were able to achieve temperatures generally considered adequate for good composting.

The compost piles of dairy waste solids dried very slowly. There were no differences in drying rates between the two (2) aeration methods or between the two (2) pile sizes.

No consistent trends or patterns were demonstrated by the total conform populations through time with regard to treatment or level within the pile. Observations suggest that in many piles the population first declined but started rebuilding at some later point during the process.

It was anticipated that the total coliform population would decline as the temperature in the pile exceeded their normal living conditions. However, even after several weeks of temperatures above 60°C, total coliform populations of a magnitude similar to those at time zero were found in many samples.

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