-9- 



Table 3. - Costs Incurred, Each Pile (1977) 



Item Cost 



Perforated plastic pipe (48(?/foot) $ 62.00 



Wood chips ($1.50/cubic yard) 270.00 



Equipment and labor 280.00 



Monitoring of piles 52.00 



Electricity 3.00 



Capital Costs 6.00 



Total $673.00 



Cost per wet ton of sludge 16.00 



Capital expenditures spread over the life of the project; does not 

 include construction of compost pad. 



DISCUSSION 



The largest single nonlabor cost in composting is for wood chips. 

 The costs quoted (Table 2) may be slightly high, since the chips can be 

 used more than once. The chips have been satisfactorily reused by simply 

 mixing the compost with more sludge; but to use the chips in more than 

 two or three cycles, fine particles need to be removed by screening. To 

 do this, a rotary screen is necessary, thus adding to the fixed costs. 

 (Rotary screens can be rented, but the cost is prohibitive.) Additional 

 handling costs and the need for extra equipment may offset the savings 

 gained by re-using the chips, unless the handling facilities are capital- 

 ized with a new plant as in Durham's new system. (See Future Plans.) Chip 

 costs can also be decreased by purchasing a chipper, providing the town 

 has an adequate supply of wood to be chipped (Table 3). 



