Spent solvent is a common by product of the flexographic printing process and its sources include inks and cleaning solvents. Spent solvent can be recycled through a distillation process. Distillation stills can be purchased or leased for on-site distillation and reuse of the solvent. There are also service providers that can either come on-site or will distill the solvent off-site. The printer may have the reclaimed solvent returned from the off-site distiller or choose to permit them to sell the material.
Best Management Practices & Pollution Prevention
Recycled solvent is often used in cleaning operations and saves the printer the cost of buying virgin solvent as well as reduces the volume of hazardous waste and associated handling and disposal costs. Prior to the recovery process, the waste solvents should be used as much as possible. For example, solvent that is slightly contaminated can be used for noncritical cleaning operations such as parts washing or the first step in a multi-step roller cleaning operation. Solvent recycled on-site may need to be restored before it can be reused.
For access to vendors who may supply alternative materials and equipment, see the PNEAC Vendor Directory.
Air emissions come from the process of distillation. The printer will be required to perform a mass balance calculation (total waste volume input compared to total volume of clean solvent out and total volume of still bottoms will result in the volume difference which is the air emissions (solvent loss).
A state or federal permit to operate a solvent distillation unit may be required due to the waste treatment activities and potential air emissions. The still bottoms, solids and residues removed from the dirty solvent, may be classified as hazardous waste and will require proper handling and disposal.