Several processing methods have been utilized for preparing gypsum drywall for recycling. The two major objectives of processing are separation of gypsum from the paper and the size reduction of the gypsum itself. A big issue associated with drywall processing is dust, and this is addressed by containing as much of the processing system as possible (placing indoors) or by providing water in the form of a mist to minimize emissions.
Drywall processing systems will in many cases require an air permit (appropriate regulatory authorities should be contacted - see State Contacts list).
Standard waste processing equipment (such as this tub grinder) may be used, but a screen will typically be required depending on the end-market. The control of dust is major concern.
A common practice is to integrate the grinding operation and the screening operation.
In some cases, a trommel screen can be used for both size reduction and separation of gypsum from paper.
Several vendors market self-contained drywall processing equipment. Many of these operate using some type of grinder followed by a screening system; a dust collection system is typically included. Standard size reduction devices found (e.g. tub grinders, horizontal mills) at many waste processing sites can be used to process drywall. Dust issues may need to be addressed and screening will normally be necessary. Trommel screens are frequently used screening devices, and in fact, trommel screens have been used as stand-alone operations where drywall is both separated from the paper and size reduced. The recovery efficiency is not as high as obtained in the shredding systems, but a preliminary size reduction step such as using a loader or compactor to provide rough size reduction is useful for increasing efficiency.
A recent development is the use of small grinders directly at the construction site; the idea is to apply size-reduced gypsum directly at the site. See the page on recycling drywall at the construction site for more information on the types of processing equipment used for this application.