Draft Cleaner Technologies Substitutes Assessment (CTSA): Screen Reclamation - Chapter 6
Overall Pollution Prevention Opportunities for Screen Reclamation
Screen reclamation is typically a chemical and labor-intensive process. During the course of the assessment of various screen reclamation methods, it was proposed that disposal of imaged screens, rather than reclamation, might be a feasible alternative. It was known that some screen printers with long production runs and extremely small screens, such as those used to print on pill bottles, simply cut the screen mesh out of the frame after completion of the production run. The question arises as to whether printers who use larger screens in shorter production runs could also feasibly dispose of their screens. By simply disposing of the screen, printers could eliminate the high cost of reclamation chemicals, labor time associated with screen reclamation, and occupational and population exposure to the chemicals used in screen reclamation, thus reducing risk. Conversely, printers would have to dispose of more screens, which could be expensive if the ink and emulsion components were required to be disposed of as hazardous waste. The time involved in preparing screens for printing, especially stretching and tensioning, would also be increased.
It would be difficult to directly compare the two options in terms of pollution prevention potential due to the different types of source reduction achieved by the two methods. While screen disposal may reduce chemical usage, screen reclamation might involve less hazardous waste disposal, particularly if filtration systems are used in the reclamation process. Other areas, such as screen performance, are also not easily defined. Some screen printers claim that screen performance improves with screen use because the tension throughout the screen mesh becomes evenly distributed. Because it is experimentally difficult to assess such claims, only a cost analysis of screen reclamation versus screen disposal was undertaken. Information on screen disposal was not collected as part of the performance demonstrations.
The cost estimate of screen disposal was developed for comparison to other reclamation methods. One cost estimate was developed to reflect the baseline facility's operations and size; it is profiled in Table VI-1. It should be noted that screen disposal is most cost effective under two circumstances not assumed for the model facility's operations: where production runs approach the useful life of a screen and where the size of the screen is relatively small. A number of assumptions were used to estimate the cost of this substitute method, including:
- No other changes in operations or equipment were required.
- Waste screens do not need to be handled as hazardous waste under RCRA, which would greatly increase the estimated cost.
- The replacement of screens (after reaching the end of the useful life of the mesh) was not considered in the baseline nor in any of the other reclamation methods; it is estimated to be approximately $0.60/screen reclamation. Consequently, this value was deducted from the total cost of this method.
- The average wage rate of screen stretchers ($6.87), which is slightly higher than for screen reclaimers, was used to calculate labor costs for this method.
Screen Disposal as a Method of Pollution Prevention
Pollution Prevention through Improved Workpractices
Pollution Prevention through Equipment Modifications
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