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April 8, 2015

 

Kristin Smith

 

There’s been a lot of hubbub lately about mixed-waste processing material recovery facilities (MRFs). As public and private waste and recycling firms work to divert more waste from the landfill, including organics, having the capability to process municipal solid waste (MSW) in addition to or instead of source-separated recyclables is becoming an attractive option.

For this issue of Renewable Energy from Waste, I interviewed several equipment manufacturers about how the equipment in a mixed-waste MRF varies from that of a single-stream MRF in the article “Processing for power.” Time and time again, I heard from equipment manufacturers about how single-stream recyclables can pretty easily be processed at a mixed-waste MRF. On the contrary, a single-stream MRF, they said, would not be able to handle MSW due to the strain it would put on the equipment from the high amounts of contamination. A mixed-waste MRF is designed to remove a majority of those contaminants at the front-end of the process. The recyclables that remain after that preprocessing step are recovered through a series of screens, air classifiers and optical sorters, almost identical to a single-stream MRF.

Many mixed-waste MRFs do process a combination of residential single-stream material, commercial and industrial recyclables, and MSW, all of which are run through the system at separate times. Because the front-end of a mixed-waste MRF applies similar technology to that of a construction and demolition (C&D) recycling facility, using a series of screens to sort light and heavy fractions, some mixed-waste facilities also handle mixed C&D debris.

Single-stream MRFs can handle a small degree of contamination, while mixed-waste MRFs have the flexibility to process a variety of material streams. As more emphasis is placed on organics recovery and acceptance of waste conversion technologies as part of an integrated waste management approach, it may make sense for companies to invest in the additional processing equipment used in a mixed-waste facility so that they are better capable to handle whatever types of material streams may come their way. As more of these facilities come online, the designs and equipment will only continue to improve so that the quality of the materials being recovered from these facilities also will improve.

In order to achieve the level of diversion being required in certain states and municipalities, or to achieve consistent feedstock volumes for waste conversion technologies along with keeping hauling costs down, at the very least, mixed-waste processing equipment investment is worth taking a look at.