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Furthermore, reduction of chip cost by re-using chips and/or by a town sup- 

 plying its own chips decreases this cost to some extent (Table 3). Accord- 

 ing to Epstein (personal communication) , a one-inch chip can be re— used 

 about five times before it is completely disintegrated. This extent of 

 re-use requires screening, which adds an estimated $1 per yard to the 

 overall cost. When all factors are considered, it is not inconceivable 

 that the cost of composting could be reduced to less than that of landfill 

 simply by initiating economies in obtaining and handling the chips. 



FUTURE PLANS 



The Town of Durham is now sufficiently satisfied with the composting 

 process that it has been incorporated into the design for a new secondary 

 treatment plant as the sole sludge handling system. So far as possible, 

 operating costs will be lowered by incorporating more permanent facilities 

 in the new plant. For example, the aeration system will be embedded in a 

 concrete pad so new pipe will not be required for each new pile. Mixing 

 of the chips and sludge will be done by a pugmill to reduce equipment and 

 labor costs. Finally, a front-end loader will be purchased for the com- 

 posting system. Thus, town equipment purchsed for other purposes will not 

 have to be used and charged off to the composting on an hourly basis. In 

 total, the estimated capital cost for the semi-mechanized system will be 

 $500,000. Ninety-five percent of this amount will be covered by Federal 

 and State funds. This leaves only $25,000 to be funded by the town. (In 

 comparison, establishment of a landfill site in Durham was estimated to 

 cost $600,000.) The estimated lifetime of the new treatment plant is 20 

 years, with an average sludge production of 43 wet tons per week over the 

 period. Thus, the per wet ton capital costs will be $23. However, the 



