▁separation ▁is ▁the ▁other ▁extreme , ▁where ▁each ▁material ▁is ▁clean ed ▁and ▁sorted ▁prior ▁to ▁collection . ▁This ▁method ▁requires ▁the ▁least ▁post - collection ▁sorting ▁and ▁produces ▁the ▁pur est ▁rec y cl ates , ▁but ▁inc urs ▁additional ▁operating ▁costs ▁for ▁collection ▁of ▁each ▁separate ▁material . ▁An ▁extensive ▁public ▁education ▁program ▁is ▁also ▁required , ▁which ▁must ▁be ▁successful ▁if ▁rec y cl ate ▁cont am ination ▁is ▁to ▁be ▁avoided . ▁In ▁Oregon , ▁USA , ▁its ▁environmental ▁authority ▁Oregon ▁DE Q ▁survey ed ▁multi - family ▁property ▁man agers ▁and ▁about ▁half ▁of ▁them ▁reported ▁problems ▁including ▁cont am ination ▁of ▁rec y cl ables ▁due ▁to ▁tres pass ers ▁such ▁as ▁trans ients ▁gain ing ▁access ▁to ▁the ▁collection ▁areas . ▁ ▁Source ▁separation ▁used ▁to ▁be ▁the ▁preferred ▁method ▁due ▁to ▁the ▁high ▁sorting ▁costs ▁in cur red ▁by ▁comm ing led ▁( m ixed ▁waste ) ▁collection . ▁However , ▁adv ances ▁in ▁sorting ▁technology ▁have ▁lower ed ▁this ▁overhead ▁substantial ly . ▁Many ▁areas ▁which ▁had ▁developed ▁source ▁separation ▁programs ▁have ▁since ▁switched ▁to ▁what ▁is ▁called ▁co - ming led ▁collection . ▁ ▁Bu y - back ▁cent ers ▁▁ ▁Bu y - back ▁cent ers ▁differ ▁in ▁that ▁the ▁clean ed ▁rec y cl ates ▁are ▁purchased , ▁thus ▁providing ▁a ▁clear ▁in cent ive ▁for ▁use ▁and ▁creating ▁a ▁stable ▁supply . ▁The ▁post - process ed ▁material ▁can ▁then ▁be ▁sold . ▁If ▁this ▁is ▁prof itable , ▁this