-6- 



During the composting process, the piles should be monitored for tem- 

 perature and internal air oxygen level. Temperatures should be recorded at 

 least daily at several locations in the pile; oxygen values of the exhaust 

 gasses should be measured in a like manner. Temperatures should be above 

 45 C. and oxygen values between 5 and 15 percent (Epstein and Wilson, 



1975). It usually takes two to three days for the temperature to reach 

 45 C. If the temperature of the pile rises to over 60 C. , there is prob- 

 ably no need to monitor oxygen level. In the event that the temperature 

 does not rise, the cause is usually insufficient oxygen to maintain aerobic 

 decomposition, or excess cooling form too high an air flow. The required 

 temperatures are usually attained when air flow is adjusted to maintain the 

 air oxygen level at between 5 and 15 percent. 



COSTS OF OPERATION 



Capital Costs 



There will, of course, be certain costs associated with start-up and 

 operation of a forced aeration composting system. The initial costs in- 

 curred by the Town of Durham are summarized in Tables 1 and 2. 



A graded and gravel-filled pad was already available near the Durham 

 treatment plant, so no site preparation costs were incurred. However, the 

 cost of preparing a mixing and composting pad would have to be included in 

 most town's start-up costs. 



For each fan box, a two-foot square platform was placed four feet above 

 the ground on an old telephone pole to hold the aeration equipment. The fan 

 motor and the timer were covered by a removable louvered top for weather 

 protection. One 1/3 horsepower fan is sufficient to aerate two composting 

 piles. 



