Materials sorting can keep trouble at bay as well as upgrade recycled products.
Attendees at the 2012 C&D Recycling Forum, held in Long Beach, Calif., in September, heard from two presenters on why recyclers C&D materials will continue to invest in automated sorting equipment.
Rick Comtois of Austin AI, Austin, Texas, reminded recyclers that scrap wood treated with chromated copper arsenate (CCA) will continue to enter C&D recycling facilities in the decades ahead.
Wood was treated with CCA as a barrier to prevent bugs and rot from eating into railroad ties, fence posts and other outdoor applications, particularly in the humid Southeast.
According to Comtois, CCA, which contains both arsenic and chromium, is unwelcome in mulch materials and in many boiler or energy applications. Although CCA has not been used since 2000, CCA-treated wood remains in use at many sites yet to be demolished or renovated.
Both because treated wood can be hard to spot (especially after it weathers) and because recyclers need to keep materials moving at a steady pace, Comtois says he has been working on automated techniques to sense and then segregate CCA-treated wood.
The system Austin AI has designed uses an X-ray fluorescence (XRF) sensor to detect copper, chromium or arsenic; and then air jets eject these pieces. The device, according to Comtois, is best used after a secondary shredding stage so the air jets can push the detected pieces far enough.
Comtois told attendees Austin AI is seeking “an industry partner to take the technology to the production stage [if] indeed there is a push to get CCA-treated wood out of the stream.”
At the same session, presenter Wilfred Poiesz from the Torrance, Calif., office of Van Dyk Recycling Solutions, noted that recyclers and their equipment suppliers have been re-adjusting their sorting equipment to handle an increase in commercial (non-C&D) materials heading into what were traditionally mixed C&D recycling facilities.
Poeisz says this commercial dry waste can comprise “up to 60 percent of the stream at some facilities, to compensate for the lower availability of C&D materials.”
When setting up to maximize returns on automated sorting, Poeisz stated that in both commercial dry waste and in future C&D materials streams, “increasingly, plastic is going to be a large factor in your material income.”
The C&D Recycling Forum was Sept. 23-25 at the Hilton Long Beach & Executive Meeting Center, Long Beach, Calif.