▁conser ves ▁the ▁emission ▁of ▁green house ▁g ases ; ▁if ▁un prof itable , ▁it ▁increases ▁the ▁emission ▁of ▁green house ▁g ass es . ▁Government ▁subs id ies ▁are ▁necessary ▁to ▁make ▁buy - back ▁cent res ▁a ▁vi able ▁enter prise . ▁In ▁ 1 9 9 3 , ▁according ▁to ▁the ▁U . S . ▁National ▁W aste ▁& ▁Rec y cling ▁Association , ▁it ▁costs ▁on ▁average ▁$ 5 0 ▁to ▁process ▁a ▁ton ▁of ▁material , ▁which ▁can ▁be ▁res old ▁for ▁$ 3 0 . ▁ ▁In ▁the ▁US , ▁the ▁value ▁per ▁ton ▁of ▁mixed ▁rec y cl ables ▁was ▁$ 1 8 0 ▁in ▁ 2 0 1 1 , ▁$ 8 0 ▁in ▁ 2 0 1 5 , ▁and ▁$ 1 0 0 ▁in ▁ 2 0 1 7 . ▁ ▁In ▁ 2 0 1 7 , ▁glass ▁is ▁essentially ▁val uel ess , ▁because ▁of ▁the ▁low ▁cost ▁of ▁sand , ▁its ▁major ▁component ; ▁low ▁oil ▁costs ▁th w arts ▁pl astic ▁rec y cling . ▁ ▁In ▁ 2 0 1 7 , ▁Nap a , ▁California ▁was ▁re imb urs ed ▁about ▁ 2 0 % ▁of ▁its ▁costs ▁in ▁rec y cling . ▁ ▁Drop - off ▁cent ers ▁▁ ▁Drop - off ▁cent ers ▁require ▁the ▁waste ▁producer ▁to ▁carry ▁the ▁rec y cl ates ▁to ▁a ▁central ▁location , ▁either ▁an ▁installed ▁or ▁mobile ▁collection ▁station ▁or ▁the ▁re processing ▁plant ▁itself . ▁They